It’s time for our Spring edition of People and Plants. This time we’ll be taking a look at the life and accomplishments of Asa Gray.
Asa Gray in 1864 CC image
Asa Gray (November 18, 1810 – January 30, 1888), now considered the most important American botanist of the 19th century, had very humble beginnings. He was born in the back of his father’s tannery in Sauquoit, New York, the eldest of eight children. From childhood Asa was an avid reader. After completing grammar school in 1825 he attended the Fairfield Academy in Herkimer Co., New York and then went on to the Fairfield Medical College in 1826. It was then he began mounting botanical specimens. He got his medical degree and did eventually open a practise in Bridgewater, New York but never really “made a go of it”, he enjoyed botany much more. So much more that in the fall of 1831 he basically gave up his medical practise to devote more time to the study of plants.
By 1832 he was trading specimens with botanists not only in America but also in the Pacific Islands, Asia and Europe. In early 1836 he became curator and librarian at the Lyceum of Natural History in New York, now called the New York Academy of Sciences, he resigned in 1837. In 1838 he took a position at the newly established University of Michigan as the Appointed Professor of Botany and Zoology. This position was the first devoted solely to botany at any educational institution in America. He was soon dispatched to Europe to purchase books to start the university’s library and for equipment, such as microscopes, to aid research. He spent a year traveling around Europe, visiting gardens and meeting important botanists of the day including William Hooker in Glasgow, Jospeh Descaisne in Paris, Stephan Endlicher in Vienna, and Augustin Pyramus de Candolle in Geneva. He returned to the USA in 1841. Some trip, eh?
Gray in 1841 CC image
While he was in Paris at the Jardin des Plantes Gray came across an unnamed dried specimen, collected by André Michaux, and named it Shortia galacifolia. Over the next 38 years he spent considerable effort looking for a specimen in the wild. The first expedition in the summer of 1841 to an area in Ashe Co., North Carolina was unsuccessful. Further expeditions yielded the same negative results. In May 1877 a North Carolina herb collector found a plant he couldn’t identify. It was collected and sent to Joseph Whipple Congdon who contacted Gray telling him that he felt he’d found Shortia. Gray was thrilled to confirm this when he saw the specimen in October 1878. In spring 1879 Gray led an expedition to the spot where S. galacifolia had been found. Unfortunately, and much to his disappointment, Gray never saw the wild species in bloom.
Shortia galacifolia – 2013. Photographed in Oconee County, South Carolina. CC image
In 1841 Gray was elected to the American Academy of Arts and Sciences. In 1842 he accepted the offer of a position at Harvard University. It included a salary of $1,000/year, teaching only botany, and being the superintendent of Harvard’s botanic garden. Though the salary was low the position allowed him plenty of time to do research and work in the garden. He was only 32. At the time he had a priceless collection of more than 200,000 preserved plants, many of which he named as new species, and 2,000 botanical texts, which he donated to Harvard to found its botany department.
Asa Gray, the early years at Harvard CC image
In the summer of 1844 Gray moved into what became known as the Asa Gray House in the Botanic Garden. As an academic, Gray was considered a weak lecturer but was highly regarded by his peers for his expert knowledge. He was better suited to teaching advanced rather than introductory classes, which he found tedious. He eventually became well known by the outside of academia for his prolific writings and textbooks.
Asa Gray House
His first book, TheElements of Botany was published in 1836. In it Gray championed the idea that botany was useful not only to medicine, but also for farmers. His next work Flora of North America, co-authored with John Torrey, was published in 1938. By the mid-1850s he had become so well-known that he wrote two high school-level texts in the late 1850s: First Lessons in Botany and Vegetable Physiology (1857) and How Plants Grow: A Simple Introduction to Structural Botany (1858). The publishers pressured Gray to make these two books non-technical enough so high school students and non-scientists could understand them. A prolific writer, he was instrumental in unifying the taxonomy of North American plants. The most popular book was his Manual of the Botany of the Northern United States, from New England to Wisconsin and South to Ohio and Pennsylvania Inclusive, known today simply as Gray’s Manual. Gray was the sole author of the first five editions of the book and co-author of the sixth, with botanical illustrations by Isaac Sprague. Many editions have been published and it remains a standard in the field.
Illustration from Gray’s Manual of the Botany of the Northern United States
Gray also worked extensively on a phenomenon called the “Asa Gray disjunction” which is the surprising morphological similarities between many eastern Asian and eastern North American plants.
Before 1840 Gray’s knowledge of Western US plants was limited to specimens sent him by collectors and colleagues working in the field. He worked with George Engelmann, Ferdinand Lindheimer, and Charles Wright who all collected widely in the Southwest including Texas, New Mexico, and parts of northern Mexico. Accompanied by his wife, Gray finally traveled to the American West on two separate occasions, the first by train in 1872 and then again in 1877. Both times his goal was botanical research and sample collection to take back to Harvard. His collecting companion on these trips was Jospeh Dalton Hooker, son of William Hooker whom Gray had met in Glasgow on his first trip to Europe in 1838. Gray’s and Hooker’s research was reported in their joint 1880 publication, “The Vegetation of the Rocky Mountain Region and a Comparison with that of Other Parts of the World,” which appeared in volume six of Hayden’s Bulletin of the United States Geological and Geophysical Survey of the Territories.
Asa died in January of 1888 after suffering a stroke two months prior.
Aesculus discolor by Gray, from Plates Prepared between the Years 1849 and 1859 to Accompany a Report on the Forest Trees of North America Public domain image
As I write this, about half of the lower 48 United States has passed the median date of the last freeze according to the National Centers for Environmental Information. Here in the Southeast, we are well into the planting season even though our usually early planting for crops like corn was delayed due to very wet soil. The rest of you may have to wait for a few more weeks before you can put any heat-loving plants into the ground. As we enter the growing season for the majority of the country I thought it might be helpful to take an updated look at what we expect this summer and fall to give you an idea of what conditions you might experience.
What factors will control the climate this summer?
In the Southeast most gardeners say that you should not plant summer crops and flowers until after Easter, although since Easter has a variable date that can sometimes be a problem when it is unusually early. In western Michigan where I grew up my grandmother always told me to wait until after Memorial Day. What rule of thumb do you use? If you look at the map below, you can see why! Wherever you garden you need to know the specific weather and climate to expect in your location. That includes things like the plant hardiness zone, how much rain to expect, and the specific microclimates within your garden (especially if it is a large one). That will help you pick the plants and trees that will do best in your location.
Every year is unique in terms of what temperature and precipitation patterns occur, but in many parts of the country we can get some indications of what might occur due to large-scale climate patterns that are occurring across the world. Of course these also affect the weather in other places from Europe to Australia and points in between, but I am going to focus on the US in this post.
As temperatures rises around the globe we can expect both daytime high temperatures and overnight low temperatures to increase in temperature. In most areas the minimum overnight temperatures are rising faster than the daytime highs. This is due to a combination of increased humidity caused by increases in evaporation and more water-holding capacity of the air and heat-trapping in urban areas due to pavement and buildings. You can determine trends in temperature and precipitation for your location using the “Climate at a Glance” tool for anywhere in the continental US, including maximum and minimum temperature. The increased humidity will increase the likelihood of fungal diseases in plants that are susceptible so you will want to watch carefully and be prepared to treat them. You should also watch for protracted hot, dry spells and increased water usage, which might require you to water more often. But keep in mind that while the average temperature might be warmer, there will still be ups and downs with the daily weather.
We are currently in a waning El Niño (EN) after experiencing a strong EN over the winter. The winter weather pattern showed a very clear EN pattern over most of the country (and other parts of the world for that matter) with unusual warmth and dry conditions in the northern US and wet, somewhat cooler, cloudier conditions in the southern part of the country although that was tempered by the long-term temperature trend upward. The current EN is expected to disappear rapidly over the next few months and swing to the opposite phase, La Niña (LN), by mid to late summer as shown below. I also discussed this back in February. This LN will likely control our weather for a good part of the rest of 2024 and into the spring of 2025.
How will this affect the growing season weather in the US? While the correlation between LN or EN and summer weather is less strong than the winter correlation, we do expect to see some lingering effects of EN for the next few months before LN kicks in. That means wetter conditions are likely to continue in the southeastern US for the next few months before dry and sunny conditions move in later this summer or fall. The timing of when that transition occurs depends on how quickly the transition from EN to LN occurs. It is changing right now, but it’s still too early to tell how soon it will affect our summer weather. In the northern US we will probably see more seasonal weather for the next few months but next winter is likely to be much colder and wetter than last year. Again, the transition should occur later this summer but could wait until late fall to really become apparent. Some areas like the Central Plains are not very predictable by the phase of EN or LN so we are less certain about what you will experience if you live there. You can see the lack of certainty in the May-July temperature map below.
The warm Atlantic and what we expect from the Atlantic
tropics this year
Last year, we had 19 named storms plus three other unnamed storms that were close to tropical status. This is in spite of the El Niño, which usually suppresses development of tropical systems because of strong winds aloft that keep tropical storms from developing the vertical structure they need to grow. Most of those storms stayed over the Atlantic Ocean where the water temperatures have been at record-setting levels for over a year. They are still at record-setting levels now and are even hotter than last year at this time. This year with a La Niña there is not much to keep storms from developing so I expect to see more storms, especially in the western Atlantic and in the Gulf, where they are more likely to come onshore and do damage or drop a lot of rain along their paths. I have seen predictions of as many as 33 named storms this year, although that would be a record and climatologists don’t generally like to forecast record values. A more conservative value of mid-20s for named storms seems more likely, although this is still a lot more than we usually get. What you actually experience depends critically on the path that the storms take, which cannot be predicted until after the storms form. So you could get hit directly by strong winds and heavy rain or you could be in the area outside the path with clear skies, sinking air, and no rain at all.
No matter how many named storms we get, those of you who live in the eastern US where a hurricane or tropical storm (or their remnants, which can also carry flooding rain to places far away from the tropics) can travel should be watching carefully when the storms start popping later this spring or early summer. Conversely if you live in the western US, you may see less activity this year than last year since when LN is strong, the Eastern Pacific Ocean (EPO) storms have a harder time developing due to the colder ocean water in the EPO associated with LN. But with rising global temperatures we are in uncharted territory so surprises are always possible.
What NOAA’s Climate Prediction Center predicts
The combination of all of these factors (and other climate influences
as well) is collected into NOAA’s Climate Prediction Center maps. I have shown
the one for May through July 2024 below. It shows the likelihood of wet
conditions in the Southeast and drier conditions out west associated with the
lagging EN conditions. You can see maps for other time periods at Climate
Prediction Center – Seasonal Outlook (noaa.gov).
For gardeners, if you are in the region where frost is still likely, you should hold off on planting tender vegetables and flowers at this point or at least start them inside. If you are in the southern reaches where frost is no longer likely then you can (and probably are already) plant the summer flowers and vegetables you are craving to set out, as long as no cold outbreaks are predicted. If you live in an area that is affected either directly by tropical storms and hurricanes or indirectly by heavy rains that remain after the storm has weakened now is a good time to clear out dead limbs and other potential flying debris, think about drainage in your gardens in case of heavy rain. Please make your hurricane plans in case one tracks over you (you can find one for Georgia at https://gacoast.uga.edu/wp-content/uploads/2020/08/ResidentsHandbook.pdf but most of the information there is relevant to large parts of the country). If you live in other parts of the country like the western states, you could see dry conditions and potential wildfires return to those areas so you should prepare for those conditions. By late fall, the La Niña should be well established and dry conditions are likely to occur in the southern tier of the US while cold and wet conditions are more likely in the northern states.
Spring with flowers. Source: Larisa Koshkina, Commons Wikimedia.
In many publications and garden resources you see the suggestion to remove flower buds to improve establishment of new fruit and vegetable plants. This advice is shared for both woody and perennial plants like fruit trees and strawberries and for annuals like tomatoes and peppers. And whenever you see someone stating this as gospel, you see someone else stating that it is false or only anecdotal. So the question is – does research support the advice to remove early plant blossoms to improve vegetative plant growth and establishment? Let’s take a look at some recent, and not so recent, research to see what really happens and understand the process.
The Physiological Process
Prior to my extension career teaching people gardening, I
fancied myself a budding (ha ha) plant science researcher. Many of my classes,
therefore, were focused on plant physiology and genetics. Not necessarily handy
in teaching people the basics of gardening, but pretty damn handy in explaining
how plant processes work.
As most upper elementary and middle school students will tell you, plants make their own food in the form of the sugar glucose by using energy from the sun through photosynthesis. That glucose is used in the respiration process to release the energy for the plant to use, transformed into other sugars and compounds for functions around the plant, or turned into starch for long-term storage. Photosynthesis is not an unlimited process and genetics, environment, and other factors play a role in the rate of energy development. So it stands to reason that there are lots of things that have to happen with the finite resources made by the plant.
In plant physiology circles, photosynthesis is called the “source” of plant energy and those uses, such as root, leaf, stem, wood, flower, and fruit production and storage are called “sinks” (sometimes also “pools”). Researchers often discuss these pathways as “source-sink” interactions. Since there are only so many carbohydrates to go around, researchers have long known that when demand is high for growth of certain structures that development of other structures is slowed. If there is a period of rapid root growth, the demand for carbohydrates in the roots increases and the availability for other locations in the plant is decreased. As a result growth in the leaves, stems, or reproductive organs may slow until a supply is restored. But this phenomenon varies by plant species and even cultivar/type, as genetics does play a role in the rate of photosynthesis. Some plants have a higher level of photosynthesis to help offset the sudden upswing of need, and some don’t.
Think of it like a household budget, but you have a job that only pays you in months that are warm and sunny. You have a set monthly income (the source) and then your housing, utilities, food, and other bills to pay (the sinks). Plus, hopefully you are saving some money for later somehow (another sink). If your bill sinks are greater than your income source, you might dip into your savings a bit, but you don’t want to take it all because you will need most of it in the months when you don’t get paid because it is cold and dreary, or your leaves have fallen off, or your herbaceous bits have died back. As a plant you don’t qualify for credit so the only way to make things work is to cut back in some areas (a sad reality for many on limited incomes). You have to reduce your utility usage, cut back on more expensive foods, find cheaper rent, etc. Similarly, a plant has to reduce the amount of energy used for, say, root growth if it has a rapid leaf growth.
And if you have a kid then the expenses go way up, right? That’s what happens when a plant is just minding its business, enjoying a free and frivolous lifestyle when all of a sudden reproduction comes along. First flower structure development, then fruit development. Plants that have a higher rate of photosynthesis have a higher budget to pull from, so the change may be minimal. But when photosynthesis rates are low, like in newly developing plants with few leaves, unfavorable environments, or genetic limits, the effect can be significant.
So, what about my plant?
The question we always get is, “is it necessary to remove the early blossoms on my ______ plant to help it get established?” For perennials like fruit trees, that would generally be the first few years. For annuals like tomatoes, it would be removing blossoms the first few weeks after planting (and removing any blossoms developed before transplanting). The answer is…maybe. Or more like, there probably is an effect, but it depends on the plant and environment as to how impactful the effect is. This phenomenon has been observed in several species, including Douglas fir, peaches, olives, and more.
For example, research shows that letting blueberry bushes fruit the first two years after planting (not removing flowers or fruits) reduces the biomass (vegetative growth) AND the yield in year 3. The plants will likely catch up in later years, but if your goal is to get plants established early and have fuller harvests sooner, removing flowers in years 1 and 2 would be advisable.
The same can be said for strawberries. The abstract from this paper from 1953 (I couldn’t track down the full article prior to publication) says that “removal of blossom from newly set strawberry plants helps more in the establishment of a vigorous planting than almost any other cultural operation.” This paper doesn’t measure biomass, but did find that removing flowers on day-neutral strawberries (that produce throughout the growing season) until July 1 resulted in maximized yields in the later season and removal of flowers for the entirety of the first year resulted in maximized yields in year 2 (note: in commercial strawberry production, strawberries are usually grown as an annual or at most a biennial, so maximizing early yields is important).
Now, for the all important tomato (drumroll, please). This study from the 70s found that removal of early blooms on indeterminate tomato plants resulted in larger plants (higher vegetative growth) and that eventually the fruit yield nearly caught up with the controls. They found that when fruit development started, leaf growth was “markedly depressed” and root growth ceased (and there was even some root death). So while there was ultimately a small loss of yield, the result was a better established plant that would likely be able to better weather environmental and disease issues throughout the season.
And beyond establishment, flower and/or fruit thinning on plants with high floral numbers has been shown in many plants (apples, blueberries, peaches, and tomatoes, to name a few) to result in larger, higher quality fruits. The same pathways apply here – each and every fruit is a sink. The more sinks you have, the more “mouths” the plant has to feed. So flower removal is a viable production strategy for many different crops and something that home gardeners should think about if you want the biggest, and juiciest fruits on the block.
Sources:
Chanana, Y. R., et al. “Effect of flowers and fruit thinning on maturity, yield and quality in peach (Prunus persica Batsch).” Indian Journal of Horticulture 55.4 (1998): 323-326.
Dejong, Theodore M., and Yaffa L. Grossman. “Quantifying sink and source limitations on dry matter partitioning to fruit growth in peach trees.” Physiologia Plantarum 95.3 (1995): 437-443.
Eis, S., E. H. Garman, and L. F. Ebell. “Relation between cone production and diameter increment of Douglas fir (Pseudotsuga menziesii (Mirb.) Franco), grand fir (Abies grandis (Dougl.) Lindl.), and western white pine (Pinus monticola Dougl.).” Canadian Journal of Botany 43.12 (1965): 1553-1559.
Hesami, Abdolali, Saadat Sarikhani Khorami, and Seyedeh Samaneh Hosseini. “Effect of shoot pruning and flower thinning on quality and quantity of semi-determinate tomato (Lycopersicon esculentum Mill.).” Notulae Scientia Biologicae 4.1 (2012): 108-111.
Hurd, R. G., A. P. Gay, and A. C. Mountifield. “The effect of partial flower removal on the relation betwen root, shootand fruti growth in the indeterminate tomato.” Annals of Applied Biology 93.1 (1979): 77-89.
Kim, Jin-Gook, et al. “Effects of cluster and flower thinning on yield and fruit quality in highbush’Jersey’blueberry.” Journal of Bio-Environment Control 19.4 (2010): 392-396.
Link, H. “Significance of flower and fruit thinning on fruit quality.” Plant growth regulation 31 (2000): 17-26.
Michael G Ryan, Ram Oren, Richard H Waring, Fruiting and sink competition, Tree Physiology, Volume 38, Issue 9, September 2018, Pages 1261–1266, https://doi.org/10.1093/treephys/tpy114
Rosati, Adolfo, et al. “Fruit production and branching density affect shoot and whole-tree wood to leaf biomass ratio in olive.” Tree Physiology 38.9 (2018): 1278-1285.
Scott, D. H., and P. C. Marth. “Effect of blossom removal on growth of newly set strawberry plants.” (1953): 255-6.
Solomakhin, Alexey A., and Michael M. Blanke. “Mechanical flower thinning improves the fruit quality of apples.” Journal of the Science of Food and Agriculture 90.5 (2010): 735-741.
Williamson, Jeffrey G., and D. Scott NeSmith. “Evaluation of flower bud removal treatments on growth of young blueberry plants.” Hortscience 42.3 (2007): 571-573.
Trees in forests have many defects such as deadwood, cavities and fungal infections
Arborists are trained in seminars and texts that rot in trees is bad. Wood decay can constitute a “hazardous condition” which when accompanied by the tree being in a place that has a target and the tree is large, can create a “hazardous tree”. The notion of hazardous trees is a uniquely human construct that has little to do with the ecology of trees, the variety of organisms that utilizes large declining trees, and does not consider what the various defects in trees may be contributing to the environment or forest around that tree in terms of organism habitat. Humans require that trees living near them must perform appropriately otherwise get out the chain saw and make them comply. In the last decade tree care for birds and wildlife has become a popular training subject for arborists in the western United States. In Europe researchers have been popularizing the notion that large trees can become centers of biodiversity because they have many microhabitats that support numerous organisms not found on younger trees. This concept is abbreviated TreM or Tree related Microhabitat.
Cavities in trees are common TreM’s in mature trees
As trees mature and then decline, they accumulate deadwood, cavities, epiphytic organisms, excrescences, exudates, fungal decay organisms, and even accumulates of soil or pockets of water in branch crotches. Arboriculture practice tends to regard tree defects as having no value, thus we remove dead wood, cut down trees with cavities and condemn trees with wood decay sporophores. It is now accepted that the more “defects” a tree accumulates the quantity and diversity of organisms associated with that individual tree also increases. In this sense old trees become centers of biodiversity within both managed and unmanaged forests.
Decay fungi infect trees but when they produce a sporophore, that is a TreM, as it provides food for athropods, here the Pleasing Fungus Beetle takes a meal.
The health of a forest is not measured only by the quality of the wood it can produce or the number of board feet it can supply, but also by its connections to other organisms that ensure its health over time. Forests are ecosystems and require connections between organisms and diversity of organisms in order to be resilient. These organisms utilize not only living but also dying and declining trees. Ancient trees are often rich in defects and have many TreM’s.
Lichens are epiphytes that utilize tree bark and rocks as a place to grow
Tree injuries such as storm damaged branches, lightning scars, frost cracks, branch failures and and other damage are all considered TreM’s. While these are functional habitat in forests they may be quickly removed from the urban forest even if they do not pose a hazard. Now that they have apparent value, perhaps we can rethink their removal where and when appropriate.
Deadwood is an obvious TreM but so are bark folds, branch architecture, plus soil and water that accumulate in these areas
The TreM concept is derived from trees growing in forests not those in cities. TreM’s may not become a management tool for urban forestry, however there are many lessons to be learned from the TreM concept. The greater the number of microhabitats, the more organisms and connections between organisms there will be. This provides resilience even to urban ecosystems. There is strong evidence that TreM’s serve as a reservoir of organisms in forests helping to maintain their health. Using the TreM concept for non-forest trees will not change how trees are managed for many situations. Risk tolerance often trumps ecosystem services. Greater understanding of TreM’s will perhaps allow us to save trees that do not pose hazards where they would otherwise be disposed of. Some tree managers have tried to create defects in trees to enhance habitat for wildlife. This is not based in science and I do not advocate creating TreM’s for the sake of having them in trees. Fungi and other organisms find their way into trees all too easily. Until we have some science based evidence for the creation of TreM’s, I recommend against it. It’s the whole do no harm thing we have going as plant pathologists. Being aware of TreM’s and evaluating their usefulness in the urban forest is a new area of study.
Trees also create TreM’s under their canopies. Here Ramairia spp. fruits in oak/pine litter
In their field guide, Butler et al., 2020 describe 47 TreM’s that they further break down into 15 groups and 7 types. The field guide is available on line if you want to find out more about TreM’s. The research on TreM’s is nascent, and restricted mainly to Europe and Canada. This fall we will collect data in the Chiricahua Mountains to add to that body of research as part of the South Western Research Station’s Trees Course to be held the last week of September into early October.
References
Butler, R., T. Lachat, F. Krumm, D. Kraus, and L. Larrieu. 2020. Field guide to Tree-related Microhabitats. Descritpions and size limits for their inventory. Birmensdorf, Swiss Federal Insitute for Forest, Snow and Landscape Research WSL. 59 p. www.wsl.ch/fg-trems
Larrieu, L., Paillet, Y., Winter, S., Butler, R., Kraus, D., Krumm, F., Lachat, T., Michel, A.K., Regenery, B., and Vanderkerkhove, K. 2018 Tree related microhabitats in temperate and Mediterranean European forests: a hierarchical typology fr inventory standardization. Ecologial Indicators, 84: 194-207
In the last week, I’ve driven all the way from western Virginia, where the redbuds are blooming, to Tallahassee, FL, where red clover is everywhere. As I drove through the mountains north of Charlotte NC, I noticed some signs indicating that strong gap winds may blow down the valleys when atmospheric pressure patterns align to produce strong pressure gradients that drive the wind. I have discussed wind before in previous posts (“Who has seen the wind?” and “Does wind chill affect plants?”) so you can find the basics of what causes wind and some of the different kinds of local winds by going to those posts. In today’s article I want to share some different local names for winds and other local weather and invite you to share your own local weather names. Note that this is not a complete list, but I will provide links at the end that prove a bigger sample of all the names that are used around the world to denote different kinds of weather, especially wind.
Redbud trees (Cercis canadensis) along Lake Marmo, Jay Sturner, Commons Wikimedia.
Local weather names based on topography
Local mountains and valleys can cause a big variety in the types of winds we observe. Generally, these winds can be classified as katabatic winds blowing downhill and anabatic winds blowing uphill. The direction depends on the time of day due to heating but also to large-scale weather patterns that direct the flow of air. Local winds can also occur due to changes in the heights of the ridges so that where the ridges are low, air can spill over the mountains in the gaps between peaks. Winds blowing downslope can also accelerate as they move to lower elevations, increasing their strength. Those winds can be very strong because of the funneling effect of the terrain leading to warnings like the ones I saw on Interstate 77 in the northern North Carolina Mountains. Some of these local winds in other parts of the world are called the Viento Zonda (or Zonda wind) in Argentina, the Williwaw in the Alaskan Panhandle, Karaburan in Central Asia, Chinook wind along the Front Range of the Rocky Mountains in the USA, Mistral in France, and the Warm Braw in the Schouten Islands north of New Guinea. You can read more about each of these by looking online at Wikipedia or other sites (link below). Winds which are affected by topography can provide good sources of steady wind for wind farms.
One of the most interesting large-scale topography-driven winds is the Tehuantepecer in southern Mexico which begins in the Gulf of Mexico (after coming south across North America) as a north wind that crosses the Mexican isthmus and blows through the gap between the Mexican and Guatamalan Mountains. It is so strong that it can be felt as much as 100 miles out to sea. This happens several times a year, especially in winter when the wind is more often from the north, and is amazing to see on https://earth.nullschool.net/ when it happens. In fact, as I am writing this on Thursday (March 28, 2024) it is happening today! How cool is that?
Some winds are named for abrupt shifts in atmospheric temperature and humidity when air from a different source region moves in. They can be small-scale changes due to outflows from individual thunderstorms like gust fronts or can be larger-scale changes due to wind blowing an air mass with colder, hotter, or drier characteristics into the area.
Some of the winds associated with drier and dustier conditions occur near desert locations as the wind shifts to bring in air from the desert regions to replace the air that was already there. One of the most common terms for one of these is haboob, which originated in Sudan but is now used in the western U. S. (Haboob basically means “dust storm” in Arabic but sounds a lot more exotic). A haboob is associated with a wall of hot, dusty air that moves into the region from the desert, bringing low visibilities to the region (often resulting in car accidents as drivers caught unawares can be blinded by the sudden change in conditions). Other dry winds include the Khamsin in Egypt and the Red Sea region, the Scirocco in North Africa and the Mediterranean, and the Harmattan in West Africa.
Airflow into NE Georgia on January 1, 2021, causing a wedge of cold air at the surface. Source: University of Georgia Weather Network.
Cold winds include the Blue Norther, a fast-moving cold front that moves in from the north that can send temperature plummeting by 20-30 degrees in a few minutes, the Bora in the Adriatic region, the Khazri in the north Caspian Sea, the Montreal Express in New England, and the Norte in Mexico. In the Southeast US, we have what we call the Wedge, which is a shallow layer of cold air that moves south along the eastern slope of the Appalachian Mountains under northeast flow, bringing clouds, cold weather, and the chance of ice storms to the region in spring. The Wedge is partly due to topography as well, since the cold air is so shallow that it can’t move west over the Appalachian Mountains and thus is forced down to us in parts of the Carolinas and Georgia. Hot dry winds include the Brickfielder in southern Australia, the Leveche in southern Spain, and the Diablo and Santa Ana winds in California, which are also affected by air moving down from the mountains into coastal areas of the state when high pressure dominates the Southwest.
Local winds are associated with thunderstorms
In addition to the wind names associated with topography and change of air quality there are also some names that are tied to smaller weather events like hurricanes and thunderstorms. Those include the Kalbaishakhi in India and Bangladesh, the Bayamo on Cuba’s southern coast, the Pampero in Argentina and Uruguay, the Cordonazo on the west coast of Mexico, and the Borasco in the Mediterranean. Strong winds associated with thunderstorms can cause tremendous damage to gardens, trees, and buildings and can cause problems with flights and road transportation. Since it is spring and we are entering severe weather season for a lot of the US, it’s a good reminder that it does not need to be a tornado to cause significant damage—straight-line winds can be just as severe.
Red clover, Pam Knox, 2014.
Knowing your local climate is important for gardeners
Anyone who lives for a long time at a location will start to recognize the local weather and climate patterns that govern your local garden conditions. If you are really dedicated, you can even measure these variations. If you know that in certain seasons, you are more likely to experience very dry dusty air, you might consider plants that can survive those conditions with less care. If you live in an area that is subject to frequent strong local winds, you will need to plan your garden to place more wind-resistant plants where the air flow is the strongest or else construct a wind shelter to keep more sensitive plants safe. Buildings can also affect the wind flow and can cause “wind tunnels” where the air is constricted and blows faster in the narrow passage.
Note: For those of you who wonder about the title of this post, Maria (sometimes listed as Mariah) is a fictional wind popularized in “Paint Your Wagon” (Lerner and Lowe, 1951) and by the Kingston Trio (1959). The name may have originated with the 1941 book “Storm” by George R. Stewart according to my colleague Jan Null of Golden Gate Weather Services.
Sources of more local wind information
Here are some websites that have listings of additional
local winds, although none of them is a complete list, I am sure.
Wherever
whitetail deer occur they present a challenge for gardeners. The internet
offers abundant advice on this, but too often it is simplistic gardening myth
such as scattering human hair or planting garlic.
Distance shot of micro-exclosure with the protective ability clearly evident
Historically
in deer control literature there have been occasional observations that deer
hesitate to enter an area which looks too small or constrained for rapid
escape. Finally, it came time to acknowledge and test this theory.
Green Island
Preserve and the University of Minnesota Extension set about investigating this
possibility through their Regional Sustainable Development Partnership (RSDP)
program which provides support to community-benefit projects in partnership
with private citizens and organizations. The test site was a 60 acre rewilded
forest inside a small northern city. Deer pressure was heavy with resident herd
numbers varying from 16-30 animals during the trial.
This graphic represents approximate scale, small, but useful for special plants and for efforts at forest understory diversification.
The first issue was defining a “small space” for testing the theory. In all the literature only one other trial of this concept could be found. It was conducted in Wisconsin with traditionally fenced spaces ranging from 15 ft by 15 ft to 21 ft by 21 ft feet during part of one summer. The Minnesota Green Island Preserve and RSDP trial chose 16 feet by 16 feet based upon the dimensions of manufactured, ridged cattle panels. These panels are 50 inches in height and 16 ft long and tend to be readily available at Fleet or Home stores even in suburban areas. If successful, their advantage would be very easy set-up and portability at a reasonable cost.
Micro-exclosure close-up at the advent of the growing season.
What was the
result? Over 2 years of trial, this test demonstrated 95% success. Six
micro-exclosures were established and planted within forested and forest edge
locations in a zone of heavy deer pressure. During an observation period of 730
days, only one instance of deer browse occurred inside a micro-exclosure.
Notice the ease and portability of an exclosure from “Cattle Panels”
This success
rate is more impressive because these fences are not a physical barrier
to deer entry. They are strictly a psychological deterrent. This places them in
much the same class as flashing lights, sound cannon, water spray, etc., but
according to this study’s data, they’re actually more effective. All
psychological deterrents have a failure rate dependent on application,
monitoring, seasonality, rainfall, and more. But micro-exclosures show a low
failure rate, without maintenance. If a deer breach does occur, the solution is
simply to make the exclosure appear even smaller. This can be done by
stretching rope across the center holding noticeable flagging. It can be lifted
off when tending plants.
A concise photo review of the micro-exclosure concept
This is a highly promising discovery which merits further controlled testing by universities and professionals. The Minnesota Green Island Preserve and RSDP trial was specifically targeted to white tail deer predation while other ungulates present browse problems in other geographies. Rabbits were not addressed. However, until further and definitive research is conducted, citizen-scientist gardeners can contribute by testing versions of this method for themselves and adding their data to the general deer-control knowledge base. In using and testing micro-exclosures, gardeners will fare infinitely better than by spreading human hair, interplanting garlic, or buying “ultrasonic” gizmos.
This post was provided by Kent Scheer. Kent is a career sculptor with a side mission for reforestation and environmental compassion. He is the editor of three handbooks on sustainable agriculture resources and owner/ manager of a rewilded pine forest in northern Minnesota created for environmental education and awareness. You can contact Kent at kentscheer@outlook.com.
I’ve written before about my time as a trial judge for the All-America Selections program, which I did during my seven years with Nebraska Extension. I happened upon the opportunity to be a judge by accident, but really came to relish my time and the work that the organization does.
You see, All-America Selections started in 1932 as a way to actually certify the claims that newly-introduced plants were actually better than ones already available. Previously it was sort of the wild-west of claims made by everyone who had a garden catalog or wrote a garden publication. There was no way to level the playing field and certify these claims until W. Ray Hastings, the president of the Southern Seedsman Association, established the All-America Selections trial program. As a non-profit and now part of the National Garden Bureau, the organization and its volunteer judges can serve as impartial arbiters of the superiority of newly-introduced plants.
This emblem on a seed packet or plant label indicates that the plant has gone through rigorous testing and performs well in gardens across the US (and beyond).
This is especially important in this day and age of spurious
claims and piles of misinformation on the web. The organization uses a research-based
approach in determining high-quality plants with replicated trials all across
the country. Plants have to perform well in all regions of the country to be a
winner. Sometimes if a plant does well in one area but not others, it will be
considered a regional winner.
Ninety-one years later the organization still serves as the gold standard for performance in home garden plants. Judges have a track record of picking plants that are favored even decades after they are introduced. The ‘Celebrity’ tomato, winner from the class of 1984, has probably been grown by almost everyone who grows tomatoes and can be found in almost every garden catalog or seed rack. ‘Bright Lights’ Swiss Chard, class of 1996, is also a go-to favorite for almost anyone who grows chard. And while many plant cultivars come and go with trends and company closures, there are still seven cultivars from the first class in 1933 still available for home gardeners to purchase through retailers: Tomato ‘Pritchard’, Spinach ‘Giant Nobel’, Pansy ‘ Dwarf Swiss Giants’, Nasturtium ‘Golden Gleam’, Carrot ‘Imperator’, Canterbury Tale ‘Annual Mixed’, and Cantaloupe ‘Honey Rock’. You can check out their profiles on the AAS website to see where to buy them.
2024 Winners
So far there have been 10 winners announced for the 2024 garden season. It unlikely that any more will be introduced at this point, but they often aren’t announced until they are ready to go to market so there’s always a chance. I served as a judge for the edible crops (vegetables, fruits, herbs) for both in-ground and container trials so I’ll start with the edible winners. Then I’ll also share info on the ornamental winners. You can always find more information, including which seed and plant suppliers/retailers carry the plants, at the AAS website.
Broccoli Purple Magic F1
A striking purple broccoli with tight growth habit. Judges noted it for its great broccoli flavor that was sweeter and more tender than the green broccolis to which it was compared. It was also noted for its heat and stress tolerance.
Broccoli Skytree F1
This broccoli’s long stalks set it apart. They make the compact heads easy to harvest. It is also noted that the stalks themselves are tender, sweet, and flavorful so they should be eaten as well. It is noted as being uniform and early maturing. Skytree was a regional winner in the West and Northwest. Container suitable.
Pepper Red Impact F1
This is a Lamuyo pepper which is a Spanish pepper noted for exceptional sweetness. It is sweeter than your standard bell pepper. The fruits are huge – nearly 8” long and double the size of standard bell peppers. We noted that they were delicious and sweet, even when green.
Celosia Burning Embers
A beautiful and long-lasting celosia in the garden. It is noted for its bronze leaves with pink veins and bright flowers. It is well-branched, heat and drought tolerant, and long-lasting in the garden. It lasted well past other types trialed. Container suitable.
Geranium Big EEZE Pink Batik
This geranium was noted for its long-lasting flowers and large flower heads. The prolific and large flower heads have a unique pink and white mosaic design. Judges also noted that it was very sun and heat tolerant. Container suitable.
Impatiens Interspecific Solarscape ® Pink Jewel F1
Noted for the bright pink flowers with an opalescent sheen, these flowers lasted well through the season. These plants are sun tolerant and also noted as being resistant to impatient downy mildew, which has basically made it almost impossible to grow (or buy) impatiens lately. Container suitable.
Marigold Siam Gold F1
This large-flowered marigold was noted for season-long performance. It was also noted that the plants didn’t need staking, even though they were tall and had large flowers making them top-heavy. Container suitable.
Petchoa Enviva™ Pink
You might be asking yourself the same question I did – “what the hell is a petchoa?” And the answer is great – it is a hybrid cross between an Petunia and a Calibrachoa, often called Million bells. The result is a beautiful, mounding plant that is covered with large, beautiful pink iridescent flowers with yellow throats. The judges noted that plants performed well all summer, even in extreme conditions. Container suitable.
Petunia Sure Shot ™ White
The judges noted that this petunia performed like a powerhouse all season long, including extreme summer heat and weather. Most notably, the flowers kept their snow-white flowers all season, whereas many white flowers fade or get blemished quickly after blooming. Regional winner from the West, Northwest, and Great Lakes regions. Container suitable.
Verbena Sweetheart Kisses
This blend of verbena has pinks, roses, reds, and whites that were super attractive to bees and other pollinators. Judges also noted the fine foliage, which isn’t like standard verbena foliage. The plants performed well all season long, even in heat and drought. Container suitable.
Petchoa – bringing together the best of the Petunia and Calibrachoa worlds
Wrapping it up
Finding that AAS seal is a great way to assure that you’re buying high performing plants for your garden. I truly did enjoy my time as a judge, even though my trials were often “if it lives through this, it definitely deserves an award” type of gardening. Now that I’ve left Extension, I’ll no longer serve as an official judge, but I still plan to volunteer to help the Extension office and serve as an “ambassador” for the AAS program. I’m glad they’ll let me stick around!
Continuing
with the theme of Underrated Beneficial Arthropods that I brought up in my
December post about Underrated Pollinators– I will be focusing on the next
category of what I consider the trio of beneficial arthropods (which includes
pollinators, natural enemies, and nutrient cyclers).
Natural
Enemies
Natural enemies are comprised of predatory and parasitic arthropods, in which one or more life stages of the arthropod feed on other organisms, such as garden pests, thereby killing them. Many gardeners are familiar with this group which includes some of our most ‘famous’ predatory arthropods such as mantids, lady beetles, lacewings, etc. This category, however, contains a plethora of beneficials that you may not always think about because most of what they do often occurs behind the scenes.
This is also a very broad category so this post will not be a comprehensive collection of all the natural enemies out there (because there are literally countless) but will have a variety of some of the most abundant, important, and unique. Like the last post it will be grouped by order or major category of Arthropod, where I will go into examples of the rockstars within that category. I will also include several resources at the end which I used to compile this information and encourage those of you who want to dig deeper into the world of natural enemies to take a look.
Flies
Flies (order: Diptera) are an incredibly diverse group of insects which provide a wide variety of different ecosystem services. They undergo complete metamorphosis (which basically means that they have 4 growth stages starting as an egg, and a major transition from their larval form of maggots that turn into pupae, and then into the adults that we recognize as flies). As such, flies also inhabit countless different ecosystems (including terrestrial and aquatic) and can be found on every continent including Antarctica. We learned about pollinating flies in the Underrated Pollinators blog post but, like many of the arthropods that we are going to cover, flies span all 3 of the major categories of beneficial arthropods. We will discuss them a bit more in-depth in the nutrient cycler category, but for this post I wanted to highlight some examples of the cool predatory and parasitic flies that we can find in our yards and gardens.
Tachinid flies [Tachinidae] are dark-colored medium-sized flies that are recognized by the dark bristles covering the body of the adults (which look similar to house flies). This family contains over 8000 described species and can be found on nearly every continent. The cool thing about this group is that every single species of Tachinids has a parasitic larval stage and many are continually utilized as natural enemies of many common pest species. As such, these flies have also been intentionally imported into various locations for biocontrol purposes. The targets of tachinids include a variety of different arthropods including caterpillars, sawflies, grubs, adult beetles, and many more! To learn more about this awesome group of parasitic flies, check out this excellent article on Tachinids written by Susan Mahr of University of Wisconsin-Madison.
Hover flies
[Syrphidae] also known as flower flies or ‘Syrphids’ are another awesome group
(you might recognize them from their shout-out as pollinators in their
bee-resembling adult stage). Larval syrphids can be terrestrial or aquatic. You
may recognize the term “rat-tailed maggots” which refers to the aquatic larval
syrphids that have a breathing tube resembling a ‘tail’ at the end of their
body. They are used in biocontrol of a variety of soft-bodied arthropods
including aphids, mealybugs, thrips, mites, and more. To learn more about hover
flies, check out this excellent resource about their use as
a biocontrol agent from
Cornell University.
True bugs
(Hemiptera and Homoptera) contain a variety of easily recognizable garden
inhabitants that can be characterized by their piercing/sucking mouthparts.
Although there are many plant feeders and common pests in this category
(including aphids, cicadas, mealybugs, leafhoppers, scale insects, stink bugs,
etc.) there are also some excellent natural enemies that don’t always get the
spotlight. Often referred to as ‘Predatory Bugs’, this fierce category of
insects includes assassin bugs [Reduviidae], big-eyed bugs [Geocoridae], minute
pirate bugs [Anthocoridae], damsel bugs [Nabidae], and predatory stink bugs
[Pentatomidae]. They vary in shape and size, but feed in the same way: by
piercing their prey with their mouthparts and sucking out the fluids. Many are,
therefore, excellent biocontrol agents in our yard and garden landscapes. Some
are even commercially available for use in greenhouses and hoop houses/high
tunnels to suppress populations of common soft bodied insect and mite pests. To
learn more about them, check out this great article on Predatory Bugs from Colorado State University.
Wasps (order: Hymenoptera) often strike fear in many people who are unaware of the sheer diversity and complexity of this group of insects. You learned about the pollinating wasps in my last Blog post, but there are also several groups of predatory and parasitoid wasps that are commonly found in our landscapes. Predatory wasps include many different species including the commonly known social wasp species (such as yellow jackets, hornets, and paper wasps) but also include countless other predatory species. One group of these common predators includes the striking family of thread-waisted wasps [Sphecidae]. This family includes spider-hunting wasps, cricket-hunter wasps, and katydid wasps. Another common family includes the cicada-killers [Crabronidae] which are a large and intimidating-looking wasp species that are actually harmless to humans. Both of these groups of solitary wasps work similarly by paralyzing their prey (often characterized by their common names) and then bringing their live bodies back to their underground nests for their larvae to feed on.
Parasitoid
wasps are an incredibly large group of wasps which include many species varying
greatly in size and shape. If you’ve seen the movie ‘Alien’ you have an idea of
what the life cycle of these wasps is like. The mother lays her eggs in a
living host (which spans countless species of insects), and her larvae feed on
the host from within, until they emerge as adults. This includes groups such as
braconid wasps [Braconidae], ichneumon wasps [Ichneumonidae], and families such
as Aphelinidae, Scelionidae, Eulophidae, and Trichogrammatidae. Each species of
parasitoid wasp needs another species of host insect in which to complete its
life cycle, and entomologists estimate that there may be hundreds of thousands
of species of these incredible organisms! Many parasitoid
wasp species are important biocontrol agents for some very famous insect
pests (including the Emerald Ash Borer, which those of us in North America are
very familiar with). You can even purchase some commercially available species
of these parasitoids to manage certain pests in your gardens and greenhouses. There
are even hyperparasitoids
which are parasitoid wasps that specifically use other parasitic wasps as
hosts. To learn more about the incredible world of wasps, check out this great
article by Marissa Schuh from University of Minnesota.
Beetles
(order: Coleoptera) are one of the most diverse groups of insects and include groups
that fall into each of the three categories of beneficial arthropods. Although
some are pests in their larval and/or adult stages (example: Japanese beetles)
and feed on a variety of different plant structures including leaves, stems/trunks,
fruit, flowers, seeds, and roots. We are also familiar with some of these
predatory beetles (with many shining a spotlight on the easily recognizable and
lovable lady beetles). That being said, there are countless other groups of
predatory and parasitic beetles that can have a significant beneficial impact
on our landscapes.
One example of a large group of these are the predatory ground beetles [Carabidae]. This dark and iridescent family of beetles can vary in size and shape. They have distinct and powerful chewing mouthparts (mandibles) which enable them to be excellent generalist predators and scavengers. The more than 40,000 species (spanning every continent except Antarctica) are common garden-inhabitants and perform invaluable services of biocontrol in agricultural, horticultural, and home garden settings.
In addition to feeding on many insect and mollusc pests, certain host-specific groups of plant-feeding beetles are also used in the biological control of weed species (including many noxious weeds) and reared by insectaries for distribution.
Neuroptera
Neuroptera (derived
from the Greek words meaning “nerve” and “wing”) is an entire order consisting
only of predatory insects! The most famous of this group are the lacewings [Chrysopidae]
(which many gardeners recognize as an awesome predator of many soft-bodied
garden pests). This order also includes other incredible species such as
antlions or “doodle-bugs” [Myrmeleontidae], dobsonflies [Corydalidae],
mantidflies or mantid lacewings [Mantispidae], snakeflies [Raphidiidae], and
more.
Mites (subclass: Acari) are another often misunderstood group of arthropods. These are arachnids (characterized by 4 pairs of legs and two body segments). Mites feed on countless living and decaying organisms including plants, animals, fungi, yeasts, algae, mosses, and even bacteria. They range in size, though most are tiny and many are even microscopic soil-dwelling organisms. The sheer diversity of mite species (due to their very broad range of ecological roles) indicates that there may be over a million species that have yet to be described.
Many
gardeners recognize some common mite pests (such as the two-spotted spider
mite), but there are countless predatory mite species as well. Predatory
mites [Phytoseiidae] are slightly larger than spider mites, and excellent predators
of spider mites and eriophyid mites which are common plant-gall causing mites.
There are several species used in biocontrol of soft-bodied insect and mite
pests as well as commercially available ones that you can purchase.
Spiders
I am sure that no one reading this post would be surprised to find these amazing arachnids on this list. Although some species are dangerous to humans, most species of spiders will leave you alone, and are incredible predators of lots of indoor and outdoor insect pests. Many humans dislike these 8-legged organisms, though most are still understanding of the important role that they play. Spiders can be strikingly beautiful, colorful, and variable in size and shape. Although some build webs to capture prey, others are active hunters or trappers that capture other organisms on which to feed. Some are even kept as pests (I had 4 tarantulas of my own at one point, and I thoroughly enjoyed observing them daily, and handling the more mild-mannered ones). There is so much that can be said about the incredible role of spiders in our homes, gardens, and natural ecosystems that it would be difficult to condense into a short summary (and may therefore be a separate Blog post in the future since this one is getting pretty lengthy).
Centipedes
span 4 different orders including soil centipedes [Geophiulomorpha], garden/rock
centipedes [Lithobiomorpha], giant centipedes [Scolopendromorpha], and house
centipedes [Scutigeromorpha] all of which are carnivorous. This group of
arthropods is characterized by many body segments, venomous fangs, and 1 pair
of legs per segment. Although many people are creeped out by these ferocious many-legged
beasts, they stay out of the way and eat many common pests in home and garden
landscapes.
I hope that
you enjoyed reading about some of your gardening companions, and if nothing
else: I hope that it broadened your perspective of all the different critters
that share your landscape with you. Stay tuned for my next post in June, which
will cover the third and final category of beneficial arthropods: the nutrient
cyclers.
The many faces of carboard found in home gardens and public greenspaces
In the quarter century that I’ve been researching, publishing, and educating on the topic of landscape mulches, one thing has become clear: cardboard should never be used as a mulch. This viewpoint has been of great interest to gardeners; in fact, my earlier post has been the most frequently viewed post since it was published in 2015. I occasionally appended new information to the original post as needed, but the topic deserves an update.
Landscape mulching with cardboard is wildly popular but has no published research to support it.Photo courtesy of Chris Martin on Flickr.
Rather than rehashing what’s been written earlier (which can be found here, here, here, here, and here in addition to the link above), I’m providing information in a Q&A format that might be helpful:
Q: Is there research on using cardboard mulch in home landscapes?
A: Not much. To date, the only peer-reviewed research relevant to landscape soil conditions is our own work published in 2019. The abstract explains the importance of the results to landscape soil health as stated in the abstract (below):
“The orders of magnitude differences in diffusion
coefficients among the mulch materials, however, could negatively impact a
diverse soil environment such as those found in biologically rich landscapes
with higher oxygen demands. Among the mulches tested, wood chips are a
preferred method of mulching in terms of providing best gas permeability,
particularly in landscape conditions.”
This chart (derived from our 2019 study results) demonstrates the increased impairment of gas movement by different mulch types.
Q: Cardboard has been used as a mulch in agricultural production. Why doesn’t that research support using it in landscapes?
Sheet mulches, including black plastic, is frequently used in agricultural production where weed control and maximzing plant yield are the most important concerns. Photo courtesy of Wyoming BLM.
A: The goal in agricultural production is to maximize yield of an annual crop. In contrast, the goal in caring for a permanent landscape is to maintain a healthy soil ecosystem that will support plant life long term. The table below explains these differences in more detail.
Comparative criteria for intensive agricultural production, home vegetable gardens, and managed landscapes
Q: Okay, I understand that science doesn’t support using cardboard as a landscape mulch, but what about my vegetable garden? Isn’t the research on agricultural crops relevant there?
A: The research on agricultural production mulches is more relevant if maximizing yield is your most important goal. But your goals may include maintaining a healthy soil ecosystem, reducing the use of pesticides and fertilizers, and other criteria. Are you concerned about the established negative impacts that cardboard and other sheet mulches have on soil life? If so, then sheet mulches are not a good choice compared to chunky, three-dimensional mulches.
Typical agricultural soil (photo courtesy of Soil Science on Flickr)
Healthy landscape soil (photo courtesy of Jim Downer)
Agricultural soils are devoid of the structure provided by soil organisms such as fungi and roots found in well-maintained landscape soils.
Q: I like reusing cardboard packaging as part of organic weed control. Isn’t that a good enough reason to use cardboard?
A: In addition to interfering with water and gas movement into the soil environment, corrugated cardboard has chemical contaminants that you really don’t want in your soil or even your compost pile. Corrugated cardboard contains environmental contaminants including dioxin and PFAs or “forever chemicals.” No gardener should want to introduce more of these widespread contaminants into their landscape or garden soils.
Recent peer-reviewed publication looking at hazardous chemicals contained in cardboard and other recycled materials.
Table from Fernandes et al. (2023). Compare the levels of contaminants between shredded cardboard and untreated wood shavings.
As I’ve been recommending for nearly a quarter century now, the very best mulch to use for treed landscapes is arborist wood chips. There is robust, peer-reviewed science establishing the benefits of arborist chip mulches in controlling weeds, enhancing growth and establishment of landscape plants, and maintaining a functional soil ecosystem. In contrast, sheet mulches such as plastic, weed fabric, and cardboard have demonstrated negative impacts on the long-term health of landscape soils. Any resource that says otherwise is not paying attention to the research-based facts.
Arborist wood chips protect exposed soil and suppress weeds while supporting desired landscape plants
In this blog I’ve talked several times about El Niño and La Niña and how they affect climate across the Northern Hemisphere as well as their impacts on the rest of the world. We are currently in a strong El Niño with sea surface temperatures in the Eastern Pacific Ocean (EPO) that are much warmer than the long-term average. But underneath the surface the ocean currents are starting to change and the El Niño is expected to swing quickly into the opposite phase, La Niña. That will affect us in North America but also other parts of the world since both El Niño and La Niña are linked to global atmospheric patterns. Since a La Niña Watch was just issued by NOAA this week I will be talking about the changes we can expect to see over the next few months and how those changes will affect gardens and gardeners.
Daffodil crop ready, Andrew Wood , Commons Wikimedia
Review—What are El Niño and La Niña?
El
Niño
and La Niña
are opposite phases of a large-scale atmosphere/ocean pattern that is driven by
temperatures in the EPO. The pattern affects climate in many places around the
globe. It is the biggest driver of seasonal climate in the Southeast and
Pacific Northwest as well as in some other countries, especially in Northern
Hemisphere (NH) winter when it is usually the strongest.
In September 2023 I discussed the
likely impacts of the El Niño that was growing at that time and how
it would affect your winter gardens. The conditions I expected have mostly been
observed, although there are some local differences that are not surprising
considering that each event is unique. Northern states have been incredibly warm
with little snow, while in the Southeast we have had a lot of rain and cooler
(although not frigid) temperatures due to wet soils and a lot of clouds
blocking the sun. California is getting hit by one atmospheric river event
after another, so they are also very wet and are even seeing a lake
in Death Valley. I imagine they will have quite a bloom of spring flowers
when it gets warmer because of the ample moisture. What have you experienced in
your area? Did my earlier column get it right?
How is this season different than a typical El Niño winter?
Even though we have had the swings of El Niño and La Niña (collectively called El Nino Southern Oscillation or ENSO) for thousands of years as evidenced by layers in ice sheets in Peru and ocean sediments, there are other changes that are not cyclical. The rise in global temperature over time is showing up as a warming trend in all seasons but especially in winter. That does not mean we don’t see other swings in climate over time because ENSO and other atmospheric cycles are still occurring, but they are superimposed on the slowly rising temperature associated with increases in greenhouse gases so the cold outbreaks aren’t quite as severe and the warm spells last longer.
Sea surface temperature departure from normal for 2024-2-12.
Plum blossoms starting to bloom, John Morgan, Commons Wikimedia.
In addition, in spite of one cold big outbreak this winter across the eastern United States, most areas have been warmer than normal resulting in an early spring that has brought honeysuckle leaves to my yard more than a week early. You can follow the “green wave” north and see when it gets to your area or verify that it’s already there at the National Phenology Network site. I am concerned about the possibility of having another late frost like 2023 that could impact the peach and blueberry growers in the Southeast since our average last spring frost date is early to mid-March for most of the commercial peach region. There has been enough cold weather for most of the fruit-producing plants to have reached their required number of chill hours, which means the warm weather is making them ready to bloom. While I don’t see another cold outbreak on the horizon for the next few weeks, we have had frosts in the Southeast into April before so we are not out of the woods yet.
ENSO probabilities for 2024 as of mid-February.
When will La Niña begin?
Climatologists predict that El Niño will weaken through spring and we will swing back into neutral conditions by the April through June period. From there most models predict we will move into a La Niña by the June through August period. By NH fall (September through November) there is a 77% chance we will be in La Niña conditions. This has implications for the summer and especially for the Atlantic tropical season since in neutral and La Niña years the number of tropical storms that occur in the Gulf and Atlantic is higher than in El Niño years. Last year despite El Niño we had 20 named storms, much more than the average of 14 events. This was in part due to the unusually warm water. Most of those stayed over the Atlantic Ocean rather than make landfall due to the presence of a strong jet stream high in the atmosphere which disrupted the development of storms farther to the west and prevented a lot of damage to us in the United States. In spite of that, we still had Hurricane Idalia and Tropical Storm Ophelia, both of which caused a lot of damage to infrastructure and agriculture.
With La Niña fully in place by fall, there will be little to stop the development of tropical storms in the Gulf and Atlantic Ocean except for Saharan dust and unfavorable weather patterns in the United States that could at least shunt any storms away from land. Some early unofficial predictions are for 25 or more named storms to occur this year, although the official predictions are still a few weeks away.
Next winter, we can expect La Niña to control a lot of our climate. That means warmer and drier conditions across the southern part of the United States while cold and wet conditions return to the northern states. Here in the Southeast, that means soil could be pretty dry in spring 2025 leading to issues with planting although it will be easier to drive heavy equipment into the fields than I expect will happen this year.
Field with daffodils, Txllxt TxllxT , Commons Wikimedia
What does all of this mean for gardeners in the United
States?
Because of the recent warm conditions associated with rising
temperatures and enhanced by El Niño in northern parts
of the country, spring is coming early to many places. That can be a good thing
if you like flowers and don’t like snow, but it does mean that your early
flowers will still be susceptible to frost damage if we get another cold
outbreak later in March or even into April or May for northern states. So you
will need to be prepared to protect the tender plants if a frost or freeze
occurs.
The end of El Niño and the eventual rise of La Niña also has implications for areas that are affected by tropical systems. This includes the Gulf and East Coasts and areas downwind of those locations but can also include parts of California and the Southwest which can see impacts from tropical systems in the EPO west of Mexico. Rainfall could be hit or miss in the late summer depending on where the storms go. You should prepare well in advance of June 1, the official start of the season, because the warm ocean water could allow tropical storms to develop in May ahead of the “official” start. That means making sure you remove damaged limbs or other objects that could become wind-borne debris, make sure you have adequate drainage for heavy rain, and keep an inventory of your belongings that could be washed or blown away in a storm. Have a family plan to keep in touch and evacuate if you need to, including pets and livestock. You can find a lot of good information on preparing for and recovering from natural disasters in this University of Georgia handbook, even if you are not in Georgia or the Southeast.
While the current warm weather makes gardeners eager to get out in their plots and get started, it’s probably too early to start in most of the country except the most southern areas. But you can dream and start planning for the warmer weather soon to come!
