Sometime in the last twenty years or so, the word “chemical” has become a dirty word. Hard to pronounce words. Unnatural synthesized substances. Mad scientist concoctions brewed in a laboratory.
I used to try to introduce some perspective when I facilitated pesticide workshops for the general public by teaching how scientists and regulators determined toxicity, so comparisons between familiar substances, like caffeine, aspirin, or detergents could be made, to varying degrees of success.
It was the “unnatural synthesized substances” part that I had the most difficulty overcoming.
James Kennedy, a chemistry teacher in Australia noticed the same problem, and started a blog and outreach effort, using infographics to illustrate the chemical make up of familiar fruits and vegetables.
As a high-school chemistry teacher, I made these posters for my students as a visual introduction to our organic chemistry course. I want to erode the fear that many people have of ‘chemicals’, and demonstrate that nature evolves compounds, mechanisms and structures far more complicated and unpredictable than anything we can produce in the lab.
The success of the basic chemical makeup posters led further to include the evolutionary history of fruits and vegetables from their wild ancestors, as explained in this Brad Plumer article at Vox.
Fruits and vegetables have changed a lot since the onset of agriculture 10,000 years ago, as generation after generation of farmers artificially bred crops to select for more desirable traits like size and taste.
But that change can be hard to visualize. So James Kennedy, a chemistry teacher in Australia, created some terrific infographics to show just how drastic the evolution has been.
One of my favorite bumper stickers from days gone by said simply “Stop Continental Drift”. Good luck with that.
Today’s topic deals with another type of drift – a phenomenon one of my professors referred at ‘Bibliographic drift’. This type of drift occurs when authors cite a paper without bothering to look up the original source. Then a second author cites original source based on the first author’s paper; then a third author cites it based on the second paper and so on and so forth. This is why grad students learn that second citing is a cardinal sin.
It’s an easy trap to fall into even in the age of access to electronic journals. It can happen in all sorts of ways, especially if the point the author trying to support is something that is intuitively appealing and not likely to be questioned. For example, I was recently reading through The Practical Science of Planting Trees by Gary Watson and E.B. Himelick. It’s a good book with lots of great info and photos but under the section on digging the planting hole there is a subsection “wider is better”. This is something we all ‘know’ but there is no data with any scientific rigor to support it; at least not that I’ve ever been able to find and I’ve looked repeatedly. So I was intrigued to see Watson and Himelick cite four papers to support the notion that wider is better. Cool. So I went through the bibliography to look up the citations.
First up, Arnold and Welsh 1995. Effects of planting hole configuration and soil type on transplant establishment of container-grown live oak. J. of Arboriculture 24:213-218. This paper doesn’t even discus planting hole width, at least not directly. The authors looked at various planting hole configurations (round, square, star-shaped) but made a point to keep the planting hole volume the same. Zero points for wider is better.
Next, Corley 1984. Soil amendments at planting J. Environ. Hort. 2:27-30. One of the experiments in this paper compared root and shoot growth of four shrub species transplanted from #1 containers into holes that were with 1.75x or 3.5x the width of the root-ball. The author measured root and shoot growth after two years and the results were a mixed bag. They found the wider hole was better about half the time, the other half of the time it didn’t make a difference. One point for wider is better (sort of).
Next, Montegue et al. 2007. Influence of irrigation volume and mulch on establishment of select shrub species Arboriculture & Urban Forestry. 33:202–209. The title of the paper says it all; the authors compared water relations and growth in response to mulch and irrigation but planting hole size wasn’t included as a variable. (Spoiler alert: mulch improved growth and water relations). Zero points.
Last and most interesting, Watson et al. 1992. The effect of backfill soil texture and planting hole shape on root regeneration of transplanted green ash. J. of Arboriculture 18:130-135. In this study the authors looked at new root growth and shoot and diameter growth for three years after transplanting green ash trees into planting holes that were 1.2x, 2x, or 3x the width of the root ball. And they found… nothing. Well, not nothing but they didn’t find any effects of planting hole size on root density, shoot growth or caliper growth. To help visualize the response I’ve summarized their growth data three years after transplanting below. One point for it doesn’t matter.
As a final note I include a photo from the Waston et al. paper 1992. The photo is fuzzy but the caption should be clear.
So where does that leave us? Digging a wider hole doesn’t hurt, except maybe your back. And I think that’s part of the appeal of this advice: If it’s more work it must be better. Dig a hole 2 times, 3 times, 10 times the width of the root-ball if you want. Just don’t say “Research shows wider is better…” because it’s ambiguous at best.
I often get horticulture questions from county extension agents, Green Industry professional, gardeners and my next door neighbors. One of the most common questions I get is why their plant did not flower that year. There are many reasons why a plant, either woody or herbaceous perennial, will not flower and both new and established plants can be affected. Some of the below reasons are obvious, some not so obvious.
There may be several reasons why a landscape plant does not flower (more to come next week):
1) Plants requiring full sun are not receiving enough sunlight.
Sun loving plants require at least six hours of direct sunlight per day to produce flower buds
Flowering is significantly reduced in areas with too much shade
Foliar diseases may be increased, such as powdery mildew, as foliage stays wet longer after rain
Growth is tall and “leggy” with most of the foliage and flowers occurring at the top of the plant
2) Transplant shock may result in little to no flowering 2-3 years after planting.
After planting, woody plants are using energy to establish a root system to support future leaves and flowers
Make sure plants are receiving enough water to encourage root growth and plant establishment
For trees, it may take longer than 3 years to produce new flowers
3) A plant may not flower because it is not cold hardy to your area.
If you live in U.S.D.A. Cold Hardiness Zone 4 and plant is rated to only zone 5, buds may be killed over winter
For some plants, like forsythia, vegetative (leaf) buds can be a half to one zone more cold hardy than the flowering buds
Make sure to select a plant and cultivar rated to your cold hardiness zone
4) In warmer cold hardiness zones a plant may not receive enough chilling hours in winter to break dormancy.
Chilling hours are the total amount of time during winter below a certain temperature, called vernalization
Required temperature are either below freezing, 0° C (32°F) or below 7°C (45°F) for temperate species
Plants suited for colder climates, like common lilac (Syringa vulgaris), require at least 3 months of cold temperatures in order to break dormancy and bloom in spring
In areas with mild winters, these plants may not flower or set fruit
Low chilling hour requiring plants are available for warmer areas
There is no definitive data on number of chilling hours required for all species
5) Severe late spring frosts can kill flower buds coming out of dormancy or emerging buds.
Developing spring buds are in advanced stages of development with minimal cold hardiness
Flowers can be killed or severely deformed
Especially damaging if the hard frost occurs after weeks of warm temperatures resulting in budbreak
Little to no fruit is produced that year; a serious problem for fruit growers
6) Pruning trees and shrubs at the wrong time of year will remove flower buds.
Flower buds are produced during the preceding summer for spring flowering plants
Prune within two weeks after flowering in spring
Avoid pruning in mid to late summer as next year’s flower buds are developing for next year’s bloom
Can prune large, suckering shrubs in dormant season, but realize flowering will be reduced that year
For summer flowering shrubs, late winter to early spring before growth begins is a great time to prune as flower buds have not developed yet for that summer
7) Flowering can decrease significantly on older, overgrown shrubs like lilacs, forsythias, chokeberries, and spirea.
Larger diameter branches have reduced flowering as the stems age, especially for lilacs
Flowers may only be at the very top of the plant out of sight and smell
Large, suckering shrubs need renewal pruning, also called thinning
Depending on the species, every 1-3 years, remove about a third of the largest diameter branches (greater than 1.5” in diameter) back to the base of the plant to allow light penetration
Regeneration of new suckering branches will occur at the base of the plant that produce new flower buds the second or third year and fill in the plant
Thinning (renewal pruning) also preserves the overall plant shape
Never shear flowering shrubs as you will be removing flower buds and ruin the plant form
Renewal pruning should only be done for shrubs that sucker
Do not attempt this type of pruning on evergreens or slow growing plants
8) A tree or shrub may be alternate bearing with heavy blooming one year and sparse flowering the next year.
Common with some trees, such as Japanese and Peking tree lilacs (Syringa reticulata and S. pekinensis), and flowering crabapples (Malus spp.)
There is little a gardener can do to avoid this from occurring
If the fruit is not ornamental, removal of old flowers before fruit set may redirect a plant’s energy into flower bud production for next year’s bloom instead of fruit production this year
Select plants that reliably flower each year if you do not want to miss the show
I was checking my eggplants today, and watching the bumble bees getting busy with the large purple flowers. As they flew in, buzzing away, they landed on the flower and kept buzzing — but the note changed, dropping in pitch. The bumble bee hummed away for a while, then flew off to the next flower.
I was watching buzz pollination at work. Egg plants, and a lot of other flowers, don’t leave their pollen hanging out in the open where any ant or fly that happens by could eat it. Rather they wrap them up in little packages that, when vibrated at just the right rate by a buzzing bumble bee, sends the pollen shooting out, so that bumble bees, which pollinate effectively, can access the pollen, but other insects, that would just eat it all, can’t.
In the garden, it isn’t easy to catch a glimpse of the pollen spewing forth, but luckily there are videos. Thank goodness for youtube. Watch it, and next time you are in your garden and hear a bee land in the flower and suddenly change the tone of its buzz, know you are seeing — and hearing — buzz pollination at work.
We just finished up with our 8th season of welcoming you-pickers to our back yard, which happens to include three acres of northern highbush blueberries. This has been an interesting venture – helps pay for our farm, obviously, but also presents an opportunity to connect with the “general public” outside of academia [that probably wouldn’t happen otherwise, considering we are both introverts]. Ninety-nine-point-nine percent of the folks that take the trouble to come to a you-pick are fabulous, functional human beings. We are very, very grateful for their patronage, especially since blueberries from Canada are on sale for $1.50/pint at the grocery store and take 5 seconds to plop in your cart. We do, as you might expect, get some interesting questions and comments, and the “OMG! Nature!” thing has come up a few times.
Here’s a selection of our [reasonably patient] responses to not-so-frequently-asked questions and comments that occur while handing out buckets and ringing up sales:
“No, we don’t have to plant them every year like potatoes. They are perennial shrubs.”
“The berries do indeed taste better if they are blue. Green and pink, not so much.”
“No, I cannot weigh you before and after picking to tell how many you’ve eaten in the field. Ha, ha, I’ve not heard that one before.”
“I’m sorry you saw a Japanese beetle.”
“Alas, we do not provide Wi-Fi out in the field.”
“I can’t go pick for you while you watch the sales stand. Sorry.”
“I know the picking season started one week earlier than last year, even though you were on vacation. It’s kind of a weather thing.”
“Nope, there will not be more berries ‘appearing’ later. This is sort of a one-shot deal, they flower in the spring, and that’s what you see here.”
“Yes, there may be some bees around. It’s a farm. We have bees. The name of our business is Bee Berry Farm.”
“No, we cannot put a net over three acres.” (People are very concerned as to how we are not overwhelmed with deer, birds, bears, etc.)
“I’m so sorry your child was stung while poking a stick in a yellow jacket’s nest.” (indeed very scary for all of us involved…especially the poor little guy with the stick.)
“We do not apply chemicals other than water and fertilizer. Pardon? Yes, water is a chemical.”
“Unfortunately, you cannot make your own bushes by planting these blueberries. And no, I’m not familiar with that website.”
“No ma’am, I do not know who placed excess zucchini in your unlocked car.”
Other observations made and behaviors noted:
Small children are usually not excited about roaming through a hot sunny field at 11:30 a.m. Though we salute the parents who think this might be a good experience for them.
Please do not send said hot and annoyed children to stand unattended under the sales tent, staring at the proprietor.
You would be amazed at how sound travels across a hillside; other pickers may or may not want to hear exactly what you think of your mother-in-law.
Please don’t park IN our perennial border.
It’s not fun to find a dirty diaper hiding in the bushes.
One of the coolest plants you’ll ever see is the titan arum. It varies quite a bit in height, but this one, named Odie, measured just a little over five feet tall. This amazing corm bloomed at the UNC Charlotte Botanical Gardens last week. Unfortunately the bloom only lasted for about two days, and during that time the area around it smelled just like roadkill. We are now waiting to see whether a fertilization attempt was successful. If it was then soon (a few long months) we may have baby Odies!
Long-time readers of this blog might remember a Friday quiz I gave back in 2010. It involved the slow but inexplicable decline of our dogwood (Cornus kousa). On the following Monday I revealed the reason for the decline and reported that we were moving this nearly dead tree to another location without the offending perched water table.
In 2011 I posted my first update along with photos of the new leaves and flowers. And today I reveal its obvious recovery to a fully functional if somewhat still spindly tree (several of its multiple leaders died as a result of the rotted root system).
There are several take-home lessons from this example:
1) Don’t assume that tree decline is due to a nutrient deficiency or pest/disease problems. The last thing a stressed tree needs is unnecessary additions of fertilizers or pesticides.
2) Explore soil conditions to find possible water movement disruptions. Our perched water table was discovered serendipitously with our pond installation. You can do the same with a good-sized soil auger. (I bought one of these bad boys, but haven’t had a need to use it yet. Some day…)
3) If a tree or shrub is failing, by all means move the poor thing to another location. In doing so, you may discover that the roots are still stuck in a clay ball and have not established into the native soil. Clean off all the burlap, twine and clay before replanting.
4) Be patient. If it took a while for your tree to reach its current sorry state, it will take a while for it to recover.
No, I’m not one. But the folks who run the Ask an Entomologist site are. You can ask them anything about bugs, and some of their best posts result from questions that come from kids.
Don’t think of it as a place for identification, although they’ll do their best to answer, or direct you to a good place where that can happen; think of it as a way to prompt them to explain some aspect about the science of Entomology that may not be well understood by the general public.
If you’re interested in how insects are related to one another, how they work on the inside, how they behave, current events in the news, or anything else … you’ve come to the right place.
And here’s how they addressed the identification part in a recent post, introducing the science of Taxonomy:
Please don’t take this the wrong way. We *want* to help you, we’re just not qualified. Insects make up 58% of the biodiversity on the planet, with beetles alone consisting of over 350,000 species. People who study scarab beetles may not even have the expertise to help you identify your sap beetle. Joe and I are just two people, and two people just can’t know all the bugs. That’s why we refer you to places where many people with various areas of expertise are present.
And they’re not afraid to tackle controversial issues, with explanations and links to the science to explain how something works. This one, for example, which addresses the Sterile Insect Technique (SIT) using the new process of genetic engineering to create the sterile insects.
People have asked Nancy and me a lot of questions about the sterile GMO mosquitoes the British company Oxitec is planning to release in Florida. We get these questions on a Facebook page we administrate as well as through this blog. People are really curious about what’s going on with these mosquitoes, and we’re really excited to talk about them!
Since I used to be responsible for a mosquito management program targeting the mosquitoes that spread West Nile Virus, as well as provide general public pesticide education, that post provided a great deal of clarity on the whole topic. In particular, the part about Rachel Carson and a quote from her seminal work, Silent Spring, which endorsed SIT as a way to reduce dependence on pesticides; a way to selectively manage a pest in a local area at the species level. That means zero impact on non-target species. What an exciting possibility!
I’m reviewing some literature while working on a proposal and ran across a paper by Lisa Richardson-Calfee, Roger Harris and Jody Fanelli at Virginia Tech on the effects planting date on sugar maple trees. It’s not actually the topic of the proposal I’m working on but the paper caught my eye because spring versus fall planting is one of those questions that just never seems to go away. In this particular study, balled-in-burlap trees planted at spring budbreak had more new root growth than trees planted in the fall. So does this mean spring planting is better? Not necessarily. For container-grown trees the results were basically a wash. This is fairly typical. I’ve not done an exhaustive search but I’ve looked at a fair number of studies of spring versus fall planting and they often show no clear trend or some will show spring coming out better or fall coming out better.
So why do we hear so often that “Fall is a great time to plant trees.” Well, first off, think about who is saying it. Frequently it is nurseries that are looking to unload inventory that didn’t sell during the growing season or landscapers that are looking to keep crews busy during the slow fall season. But the other part of whether fall is a good time to plant has to do with rainfall and temperature patterns. Linda Chalker-Scott is an advocate of fall planting. And for her location in western Washington – and many other locations in the West – this makes sense. If we look at average rainfall patterns for Seattle (actually Linda is in Puyallup but no one outside of the Northwest can pronounce Puyallup), planting in October – when the rainy season is getting into full swing – makes much more sense than planting in April or May before the summer dry season.
Where I live in East Lansing, on the hand, our climate has a summer maximum precipitation pattern – as does much of the Midwest. As I’m fond of telling people, there’s a reason Michigan’s Arbor Day is the last Friday in April. Spring is a great time to plant trees here because soil temps are warming and the rainy season is just getting started.
What about fall planting in the Midwest? My take is that fall is an OK time to plant trees but not necessarily the best. We typically will still have some rain in the fall but temperatures are declining quickly. Our average daily temperature in December is 28 deg. F, meaning our soils are beginning to freeze, while the average December temp in Seattle is a balmy 42 deg. F. That’s warm enough for Linda’s roots to keep growing – well, actually not Linda’s roots but Linda’s tree’s roots.
In any event, if you live in Midwest and other places with a summer max. precipitation pattern, your state’s Arbor Day is a good guide to plant trees. If you live out West in areas prone to summer drought then fall may be your best bet. This is also a another example of why it’s good to get your landscape and garden advice from local sources rather than the ‘one-size-fits-all’ advice common in many magazines and gardening websites.
Richardson-Calfee, L.E, J.R. Harris, and J.K. Fanelli. 2008. Root and Shoot Growth Response of Balled-and-Burlapped and Pot-in-Pot Sugar Maple to Transplanting at Five Phenological Growth Stages J. Environ. Hort. 26(3):171–176.
We are in the dog days of summer! Record high temperatures across the country have been reported. Let’s face it, climate change is real and the planet is getting warmer, despite record cold temperatures in winter in some areas. With climate change, there are more occurrences of extreme temperatures as well as precipitation such as severe drought, flooding, heavier than usual snowfall, etc. So, how does climate change affect gardeners? To understand the concept, we must first understand how high temperatures affect plant growth and development.
Plant temperature tolerance is the ability of any plant to adapt to a given climate at both low and high temperatures. It is obviously important to use species that not only can survive our winter temperatures, but also our hot summers. Similar to the U.S.D.A. Plant Cold Hardiness Zone map (http://planthardiness.ars.usda.gov/PHZMWeb/), the American Horticultural Society published a plant heat zone map (http://www.ahs.org/gardening-resources/gardening-maps/heat-zone-map). The heat zones are based on the average annual days with temperatures above 86°F (30°C). For example, up in my neck of the woods in Wisconsin, we have four heat zones in the state; zones 2-5 with the cooler (lower number) heat zones in the northern part of the state and the warmer heat zones in the southern and western part of the state and in urban areas. In comparison, North Carolina has seven heat zones (2-8). California has even more heat zones due to its varying climates and elevations.
Unique microclimates can be created at a specific site. Urban areas usually are slightly warmer than rural areas due to the heat island effect created by light reflection off of buildings, heat rising from sewers, and trapping of heat between large buildings. For example, trees planted close to pavement have warmer conditions in summer, than trees planted near turf, especially in the root zone, and have greater water needs. Trees and shrubs in this environment should receive, but rarely get supplemental irrigation compared to those same plants planted in the middle of a lawn or park area with cooler root areas and less heat stress to the tree.
So what does this mean for temperate woody plants?
High temperature stress is important for a number of reasons. The main effect is increased water use. However, water availability is often limited, especially in urban environments, leading to a net loss of moisture within the plant. Leaves loose water quicker through the stomates via transpiration as temperatures rise. The stomates then begin to close and the cooling effect of evapotranspiration is stopped.
Other physiological processes are impacted by high temperatures such as fewer carbohydrates available for plant growth and development, generation of plant pigments (red, purple and blue pigments) and defense used in protecting plants against insects and diseases. When plants with poor heat tolerance are grown in regions that routinely experience high summer day and night temperatures and insufficient moisture, plants will use many of their stored sugars during the evening hours and during the hottest part of the day. For many temperate woody plants, optimum temperatures for photosynthesis are below 86°F (30°C). Above this temperature, net photosynthesis declines with increasing temperatures. If this continues long term, plants can die, especially young plants that do not have many stored carbohydrate reserves and are under drought stress.
What can we do as gardeners?
Unfortunately, climate change is occurring at a fast rate and each decade is getting warmer and often drier than the preceding decade. Here’s what we can do as gardeners:
Select non-invasive, pest resistant, stress tolerant plants for your landscape
Non-drought or heat tolerant landscapes plants will require regular watering to sustain them
Use of soaker hoses or drip irrigation is better than overhead watering as the moisture is directly applied to the roots with less runoff
A plant is not truly drought tolerant until it has been established in the landscape for at least three years or more to allow for root growth, especially for trees
Some native and exotic plants can tolerate these changes, but some native species in natural areas may be lost if our climate continues to get warmer
Incorporate compost into the soil prior to planting new areas to improve moisture retention and aeration
Apply 2-4” of bark or wood chips to the top of the soil to retain soil moisture. Make sure the mulch does not touch the trunk of trees or base of shrubs. Excessive mulching (mulch volcanoes) can actually kill landscape plants by impeding air and moisture penetration and invite fungal diseases.
Cities need to avoid planting trees in tree pits (sidewalk cutouts), i.e. restrained planting areas in sidewalks along streets. These trees are under severe moisture, drainage and heat stress and do not live long. Planting areas that are wide and long work much better for tree health and longevity than planting in tree pits.