I’ve promoted root washing of containerized and B&B trees and shrubs for a few decades now. The experimental science is slowly coming along – it can take several years to determine if the practice is more successful in terms of plant survival than leaving the rootball intact. But we know how soils function in terms of water, air and root movement, and we understand woody plant physiology. So it’s pretty easy to predict what will happen when trees, whose roots are held captive in layers of stuff, are then planted, intact, into the landscape.
Maple newly purchased from nursery.
Early in spring 2021 I purchased a couple of Japanese maples to frame our garage. As always, I root washed these specimens. Here’s a play by play of what we did, and what we found.
Container removed, exposing fine roots. Some of the media has fallen away and is at the bottom of the wheelbarrow.Since we can’t see the root flare, we mark the point at which the trunk and soil meet.As we remove the container media, we find burlap and twine. And under that, a clay root ball. There is a root crown somewhere…Some beating on the clay rootball helps create some cracks where water can then help with the process.Into a nice soaky bath to loosen up that clay. The longer it sits, the more clay will slough off.We speed the process along with a directional spray of water.Jim gets his fingers into the wet clay to pry it away from the roots. Still no root crown, but you can see the Sharpie line on the trunk a couple inches above the clay.Eureka! A root flare several inches below the original media level.
After more cleaning and untangling, we have a root system ready for planting. Well, almost.
We have roots, but we still have some problems.It’s got some pretty crappy roots (from not being potted up properly at the nursery), and the remanent of a stake next to the trunk (about 4 o’clock). But there is a nice structural root to the left, with healthy fibrous branches.“Knee roots” have to go (I call them “knee roots” because they are at 90 degree angles). They have poor structure and will only continue that downward growth pattern, rather than growing outwards. The easiest thing to do is sever them when they turn downward at 90 degrees – don’t worry about removing them if they are too tightly entwined. New root growth at the cut will be directed outwards.We neglected to get “beauty shots” of our maples through the summer, but you can see one of them to the left of the New Zealand flax plant in the pot. Both maples established their root systems quickly and grew vigorously throughout the summer.Now in late October, the maples are turning color. Note the distance between the trees and the garage – this ensures that we will have little branch/building conflict as the trees grow in height and spread.Here’s one of our beauties getting ready to shut down for the winter. They thrived throughout the summer, even when we reached record high temperatures. We look forward to their continued success in years to come.
If you are still wondering why this is a cautionary tale, consider what would have happened if the rootball was planted intact:
The root flare would have been buried below grade.
There would be multiple layers of stuff between the roots and the native soil (i.e., clay, burlap, and media).
The twine circled around the trunk would girdle it eventually.
The poor structural roots would not create a stable support system.
Now, one can argue all they like that there isn’t a robust body of scientific literature to recommend this practice – and there isn’t, yet. But leaving rootballs intact creates textural discontinuities between the roots and the native soil, and poorly structured woody roots are not going to correct themselves. So why not embrace a practice that removes both the soil and root problems?
Say the word “hydroponics” or the even more mysterious sounding “controlled environment agriculture” and the image that most people conjure in their minds is of large greenhouses or artificially lit rooms filled with complex hoses and tubes using all manner of technological gizmos to pump water and nutrients to plants. True, modern ag technology does allow for some pretty amazing and technical production of food but hydroponics can be super simple and so easy that just about any home gardener can do it.
Why grow hydroponically at home?
Growing vegetables can be pretty easy and straightforward
for outdoor production – seeds, soil, water, and wait (sure, there’s a few
other steps in there), so why complicate things by growing hydroponically? Aside from the challenge and the novelty that
delights many gardeners, intensive growing with hydroponics can allow gardeners
with the smallest of spaces to grow impressive amounts of produce in a short
amount of time. Most of these systems
also do well for winter production indoors with the use of grow lights or some
good-sized south facing windows.
Hydroponic or similar-type production systems are the “craze” right now for folks wanting to grow some of their own produce at home, usually in smaller indoor spaces, but these systems can run into the hundreds or thousands of dollars making production less than economical. Plus, most of these systems require the use of pre-made plant/seed plugs that add to the expense.
Why is hydroponic production important?
On a larger scale, hydroponic and controlled environment agriculture has a few benefits that will help in feeding a growing population on a warming planet. Hydroponic production can be pretty intensive, meaning that it can grow a large amount of food in a relatively small amount of space. This makes it ideal for production in urban areas, which is important as most countries become more urbanized. It also cuts down on transportation needs to get food to consumers. This not only reduces fuel consumption but also, as we can see, makes it easier to get food to large populations when distribution becomes an issue. And as the term “controlled environment agriculture” implies crops can be grown using hydroponics in greenhouses or indoor farms no matter what the season or climate making it ideal for year-round production in areas where it is too cold or too hot part of the year to do so. This also means that hydroponics and controlled environment agriculture can be important mitigation strategies for climate change. When the temperatures or precipitation are no longer favorable for growing outdoor crops in certain areas, controlled environment ag can provide a stable source of produce with indoor production.
And as ironic as it sounds, growing hydroponically
drastically reduces the amount of water used for production. Closed systems, which either recirculate
water or grow in enclosed containers, use much less water than field production
systems relying on irrigation.
A simple system example
Earlier this year I build some super simple enclosed hydroponic systems for demonstration at our Extension office and at the county fair. My goal was to show how easy hydroponic production can be – no need for pumps, tubes, or expensive equipment. The system was so simple that I built it with my non-horticultural interns as an onboarding/team building exercise.
The system we built utilizes the Kratky method of hydroponic production – a simple system where the plant is suspended on top of a container full of nutrient solution. In a typical recirculating hydroponic system where water is moved around air is introduced into the water that then provides oxygen to the roots to avoid hypoxic conditions that damage roots. Some static systems rely on introducing air (like using aquarium air stones) to introduce oxygen but the Kratky method is even simpler than that. Instead of introducing air into the solution, the level of the solution is reduced (usually through use and evaporation) as the roots grow keeping a section of roots exposed to open air. The setup is super simple and low maintenance – no moving parts, no electricity (unless I need to use lights for indoors). Just plants, a medium to hold them, a container and a nutrient solution.
I’ve seen the systems made with all kinds of containers but we chose 25 gallon storage totes because they are inexpensive and pretty easy to come by. Having a lid that is relatively easy to cut/drill also makes these kinds of containers ideal to make multi-plant “beds” but I’ve also seen lidded buckets used as a single-plant system.
To hold the plants we used plastic net pots that you can find at garden centers that sell pond or aquarium plants (or order) that are also now common at hydroponic supply stores, if you’re lucky enough to have one in town. You can also use plastic orchid pots or standard nursery pots, perhaps adding extra holes for roots to grow out. We used 6 inch and 2 inch pots to plant a variety of sizes.
Net pots in the system, with holes made slightly smaller for them to fit and not fall in.
Next we cut holes in the lid slightly smaller than the diameter of the pots so that they sit on top and don’t fall through. You can do this by tracing and cutting with a sharp object, or use a drywall hole saw that you use with a drill to cut a perfectly round hole. We used one with adjustable sizes, rather than buying individual sizes.
And now, to plant!
The pots were then filled with an inert, soil-less medium to support the plants. We used a puffed clay stone called LECA, but you can use rockwool or hemp fiber blocks made for hydroponic starts, large particle perlite, or even something like a poly fiber filling (like used in sewing) – just something that won’t break down to hold the plants in place.
Some of the plants I had started in fiber cubes so those easily went into the LECA, but we did end up buying a few transplants. Since these were started in some sort of potting soil we had to wash as much of the soil off as we could. We placed larger plants like peppers and kale in the large pots and smaller plants like herbs in the small pots.
As for plant selection, leafy greens and herbs like basil and parsley are easiest and can use smaller containers and pots. Plants like tomatoes and peppers will need bigger containers and pots and will also require more light and heat if you are growing them indoors.
A solution for easy nutrient solutions
And last but not least – the nutrient solution. Since we are growing without soil we have to provide basically all macro and micro nutrients. We are used to supplying nutrients like nitrogen and phosphorous, but not so used to supplying things like manganese and molybdenum. This one is probably the scariest to those new to hydroponics, but there are some easy options out there for small scale production that are “off the shelf” solutions. Rather than worry about mixing up nutrients by hand, these pre-made mixes make it easy for home growers to try hydroponics. They come in two or three part sets of either liquid or solid fertilizers, because some of the chemicals used will react and precipitate out into a sludge if kept together in concentrated form. Just mix according to package directions and you’re good to go. If you are growing anything like tomatoes or peppers that require flowering and fruiting, you’ll want to make sure the formula is for flowering plants. Regular water-soluble fertilizers might do in a pinch, but for long term growth you’ll want to invest in something with all micronutrients.
Storage tote hydroponic system, sitting in the office courtyard.
If you’re planning on refining your technique, you might want to invest in a pH meter or TDS (total dissolved solids) meter to fine tune the solution based on the minerals dissolved in your water. And if you have really hard water you can usually get an additional nutrient product to account for the pH and calcium levels to balance things out.
So now we just filled the totes with the solution all the way up until the bottom few inches of the pots were covered. We kept watch on the solution and added water as needed, keeping in mind that as the roots grow out of the pot the nutrient solution level needed to be low enough to expose around 2/3 of the roots to air.
The nutrient solution is only a few inches deep in the bottom of the tote at this time, allowing roots to be exposed to air for oxygen uptake.
As the plants grow, you’ll just want to keep an eye for signs of nutrient deficiency and add nutrients to the water as needed. The solution should be completely dumped and replaced every 6-8 weeks, as the plants rapidly deplete some nutrients, allowing some to build up to toxic levels. You can typically just pour the solution out on the garden or lawn, as it only contains plant nutrients. However, you’ll want to make sure not to keep dumping in the same spot to avoid build up of salts in the area. Spraying the area with a bit of water from the hose can help wash it off of plants and start diluting it into the soil, rain and weather should do the rest of the job. But if you are in an area with little precipitation, you may also want to take care since there won’t be a lot of water to dilute the nutrient build up over time. And just remember, if you harvest and completely remove crops, pull apart and clean the system with some good soapy water and a sanitizer (bleach works well). You should do this every few months if you have a long-lived crop in the system.
In a nutshell…..
A simple system like this one can be a great way to explore a new growing technique, even for beginner gardeners. After these were set up, we basically left them in our courtyard all summer with little to no maintenance, except adding water earlier in the season and changing out the nutrient solution once. If you need a bit more info, or want to try something a little more complex, there are some great resources out there for small systems that I’ll share below.
As the climate warms the value of trees for cooling the environment around buildings, especially in cities, drives tree planting programs. Planting trees is just the first step in growing a tree in a sustainable landscape. Successful plantings require evaluation and guidance of the new tree’s current and future branch architecture. In almost every case, nursery grown trees will require some structural pruning so that a shade tree can develop strong and effective branch attachments that will support the canopy for the coming decades without failure. In this blog I cover maintenance of the newly planted tree including how to structurally prune young trees so that they develop strong and sustainable canopies.
As mentioned in earlier pruning blogs, trees do not require pruning. This is predicated on the assumption that trees are allowed to grow in the way they are genetically programmed to grow without damage. Unfortunately many container nurseries prune trees with a heading cut to the central leader in order to create branches that can further be pruned to make a “lollipop” canopy that mimics the form of a large tree. Consumers have become accustomed to this “in-pot” miniature version of a shade tree and nurseries are accustomed to producing them. Low branches are removed to enhance the tree lollipop shape. Nurseries often stake trees tightly to provide a way to keep them from being blown over in wind events and since all the temporary branches are removed from the low trunk they are top heavy and require rigid staking usually with a stake taped to the trunk. Tightly staked trees grow taller than unstaked trees and their trunks may lack caliper or taper (increase in trunk diameter lower on the stem). This requires that when these trees are planted out that they continue to be staked, otherwise they would fall over. This creates another burden in getting the newly planted landscape tree to survive—helping trees stand on their own.
This newly planted coast live oak complete with gator bag for water retains the nursery stake which should have been removed and has two other stakes because it does not have enough taper to stand on its own. There are no temporary branches low down and it has been “lolipopped” during nursery production. Branch faults such as “all branches from the same point” will certainly develop if it is not structurally pruned.Crape myrtle is notorious for lacking taper when tightly staked during nursery production. this tree retains the nursery tape and stake and has the classic lolipop shape that will require structural pruning to correct.
Nursery pruning creates two kinds of branch faults that if left in the tree canopy will lead to failure later. These result from heading the main leader of the young tree. When buds grow from the pruned tree, they often produce too many branches from the same place or two branches or new leaders that are the same size. We call these faults: too many branches from one point and codominant stems respectively. If the nursery tree retains these branches and they are allowed to mature in the landscape tree, one or more branches may break loose. Almost all structural pruning seeks to correct these faults at some point in the life of a nursery-grown landscape tree. The approaches are different depending on how long the branch fault is left in the tree after planting. Branch faults of newly planted trees are best corrected in the first year–they are easy to correct in the first few years and problematic after that. This is because when poorly attached branches grow well and attain greater size over time, they will pose a problem upon removal as pruning will leave behind a substantial wound which provides an entry point for wood decay. Structural pruning is best done in the nursery or if in the landscape, in the first year after planting.
This young oak retains the nursery stake even after several years post planting. The lolipop shape is indicative of inherent branch faults that have not been corrected
There are several goals of early pruning (1-3 years post planting): -Retain temporary branches on the stem to assist trunk growth (but keep them pruned) -Remove competing leaders (remove a co-dominant stem) – Thin clusters of branches (fix the all branches from one point fault) -Leave the first permanent branch unpruned -Subordinate all other branches to “temporary” status by heading them back – Leave unpruned branches along the stem that will take a permanent place in the crown of the tree. -Leave enough space between permanent branches to support their sustained growth over the life of a tree -Permanent branches should be spaced vertically and helically around the main or central leader
Most trees will do all of this without any pruning if they are unpruned from the seedling stage. They will shade out their temporary branches and permanent large branches will form strong attachments and uniform spacings. Heading cuts on young trees destroy their form and this should be avoided. In the next blog I will cover pruning young to mature trees.
Do you wish you had a crystal ball that could tell you what the climate will be next year when you plan your garden? So do many other gardeners (and climatologists). But while there is no magic answer, we do know that in many parts of the United States and other countries, year-to-year climate variability is strongly dominated by what is going on in the eastern tropical Pacific Ocean. This is through a phenomenon called “El Niño Southern Oscillation” or ENSO for short.
Witch Hazel Covered By Snow In The Garden. Hampshire UK. Source: Si Griffiths, Commons Wikimedia
What is ENSO and how does it affect climate?
ENSO has
three phases—a cold phase with unusually cold water in the equatorial Eastern
Pacific Ocean (EPO) called “La Niña”, a warm phase with unusually warm water in
the EPO, and the neutral phase that occurs between the two extreme phases. The
ocean see-saws back and forth between the two opposite phases on a semi-regular
pattern that usually lasts between two and five years from one El Niño to the
next. Sometimes you can have two La Niña years (or even three) back-to-back (the
end of 2021 is expected to be a second La Niña in a row), but you almost never
have two consecutive years of El Niño.
In many parts of the world, the phase of the ENSO is highly correlated with the climate. Scientists can use that relationship to predict what the climate might be like in the coming months. That is helpful for gardeners who need to know what to expect both next season and next year for planning purposes. Not all parts of the world have a climate that is well correlated with ENSO, however, and so folks in those areas will have to depend on other methods to look ahead to next growing season. Winter has the best correlation between ENSO phase and climate, while summer is much less predictable. And every El Niño and La Niña is distinct, leading to variations from the statistical pattern we expect.
How does the temperature of the tropical Pacific Ocean affect climate in other parts of the world?
You might think that unusually warm or cold water in the equatorial Pacific Ocean would not have much impact in other parts of the world because of the distances involved, but it does. Since the atmosphere flows like a river, putting unusually warm water (El Niño) into the EPO acts like putting a rock into a stream. The flow of water (or air) shifts around the rock, changing the pattern of atmospheric winds that blow weather systems around. When we are in a warm El Niño phase, the storm track shifts south and covers the southern US, leaving the northern US warmer and drier than usual. When I lived in Wisconsin, we noted that lake ice cover in El Niño winters did not last as long as other years, which made ice fishermen like my dad unhappy. La Niña shifts the storm track in the opposite direction. Because of that, La Niña winters are colder and wetter than average in the northern US since the storm track shifts north into the Ohio River Valley and sometimes even farther. This leads to cold, damp winters in the northern US. Similar correlations, called teleconnections, are seen statistically in climate records at many places on earth.
If we know what the phase of ENSO is likely to be, that tells us what climate conditions are expected in areas where there is a teleconnection between the EPO and that region. While every El Niño and La Niña is unique, statistically they do provide guidance on what to expect in that region, and most years they are correct, although once in a while a wildcard like a Sudden Stratospheric Warming will occur and give us an occasional busted forecast, as it did in February 2021.
What do we expect this year?
Right now, we are in neutral conditions following last winter’s La
Niña, but we are headed back towards another La Niña in the next couple of
months (almost an 80% chance in the November through January period). That phase
should last for most of the winter but is expected to return to neutral by spring. After that, it is too far out to make a
believable prediction. The Global
ENSO Temperature and Precipitation Linear Regressions website provides
global correlations between the ENSO phase and what kind of temperature and
precipitation anomalies to expect. In it, each three-month period shows the
relationship between the temperature anomaly of the EPO and other parts of the
world (regression) and how strong that relationship is (correlation).
In the map below for December-February (DJF) temperature, it shows that if the EPO is unusually warm (+) in an El Niño, then the northern part of the US will also be unusually warm (+) while the southern states are cooler than normal (-). The storm track over the southern US in an El Niño year brings rain and clouds to that region, keeping conditions wet and cool due to lack of sunshine. A La Niña year is just the opposite. The strong correlation in both southern and northern states shows that it happens most of the time, but in areas with little correlation, you can’t use ENSO reliably to predict seasonal conditions. If you have a hard time interpreting these maps, the website has a tab that explains it in more detail.
The bottom line
For this coming winter, I expect warmer and drier conditions than usual in the southern tier of US states as the storm track shifts north. That means more overwintering of insect pests and diseases; an early start to the growing season is also likely. The northern US is expected to see colder and wetter conditions than usual, which means a later start to the 2022 growing season but less chance of drought next year, although fungal diseases could be bad if the damp conditions continue into spring and summer. Western Europe could see warmer conditions than usual but the correlation is weak so that is not a strong forecast. Australia is likely to be colder than normal, with a fairly high probability because the correlations are high, at least near the coasts. This should last until spring, when the La Niña ends, and we swing back into neutral conditions when other climate factors become more important. In the Southeast, the summer after a La Niña ends is also a hot and dry summer due to the lack of recharging rain over the winter, so I think we have the potential for drought in the Southeast next summer.
I like catchy memes as much as the next person. They’re easily memorized and passed on. But “Save the planet, plant a tree” has always bugged me for two reasons. First, and probably most importantly, this simplistic mantra absolves people of doing MORE to improve our environment. It’s a “one and done” approach: “Hey, I planted a tree today, so I’ve done my part.” That’s hardly a responsible way to live in a world where climate change is a reality, not a theory. Planting trees (and other woody plants) needs to become part of a personal ethic dedicated to improving our shared environment, and that includes reducing our carbon footprint in MANY ways.
No and no.
Second, and more germane to this blog, is that most people don’t know how to plant trees (and that includes an awful lot of professionals who should know better). Planting trees properly requires an understanding of woody plant physiology and applied soil sciences. Otherwise, newly planted trees are likely to die due to one or more problems:
Poor plant species selection
Mature size too large for site.
Species not adapted to urbanized conditions. This includes insistence on using native species whether or not they tolerate environmental conditions far different from their natural habitat.
Gaultheria shallon does well in the forest subcanopy – not so well in urban settings
Poor/improper soil preparation
Working amendments into the soil before, during, or after planting. Your goal is to keep a texturally uniform soil environment.
Digging a hole before seeing what the roots look like. It’s like buying a pair of shoes without regard to their size.
The reality of tree roots: you can’t dig a hole until you can see what goes in it.
Poor quality roots
Most roots found in containerized or B&B trees are flawed through poor production practices. If you are using bare root stock, you don’t have to worry about this problem.
Can’t see the roots? Well, that leads to the next problem.
You can’t see root problems unless you take it all off.
Improper root preparation
No removal of burlap, clay, soilless media, or whatever else will isolate the roots from its future soil environment. Take it all off.
No correction of root flaws. Woody roots don’t miraculously grow the right direction when they are circling inward. They are woody; it’s like trying to straighten a bentwood chair.
Just try to straighten those circling, woody roots.
Improper planting
Planting at the wrong time of year. It’s best to plant trees in the fall, when mild temperatures and adequate rainfall will support root establishment and not stress the crown.
Not digging the hole to mirror the root system, especially digging too deep.
Failing to place the root crown at grade (which means the top of the root crown should be visible at soil level). Look at forest trees if you are not familiar with what a root crown looks like.
Stomping or pressing the soil around the roots. That just eliminates the air space in soil pores.
Adding “stuff” like transplant fertilizers, biostimulants, etc. They are not needed and you risk creating nutrient imbalances when you add “stuff.”
The tape marks where the burlap ended – a good 10″ above the root crown.
Poor aftercare and long-term management
Failing to add arborist wood chips as a mulch on top of the planting area. Regardless of where you live, natural woody material as a mulch is critical for root, soil, and mycorrhizal health.
Failing to irrigate throughout the establishment period and seasonally as needed. Trees will continue to grow above and below ground, and without a similar increase in irrigation the trees will suffer chronic drought stress during hot and dry summers.
Adding fertilizers of any sort without a soil test to guide additions. Trees recycle most of their nutrients; don’t add anything unless you have a documented reason for doing so.
There is nothing better for roots, soil, and beneficial microbes than fresh arborist chips.
That’s a lot to think about when you are planting a tree – but when you understand the science behind WHY these actions should be avoided, then you can devise a better plan for planting. And if it all seems to be too much, I have created a twelve-step planting plan that might be useful. Please feel free to share it widely!
As we head into Fall garden routines and leaves start to turn color, the smell and feel of the Fall weather is in the air. Winter is just around the corner and with those horticultural routines comes the urge to prune stuff . Both fruit producing and shade producing trees often get a hair cut during fall and winter months, herbaceous perennials are often cut back in the fall after bloom and before their winter rest so it seems a good time to blog about pruning before you get the urge! After years of pruning demonstrations for Master Gardeners and the public I have noted a common thread in how gardeners think about pruning. Pruning is a mysterious process. How we take that tangled mess of a plant (tree) and fix it? What do we prune? And the less frequently asked question: What do we not prune? To add confusion, some plants such as roses seem to have their own pruning “culture”. In this blog post I will cover the basic principles that apply to pruning all plants and then expand into specifics in upcoming blogs.
“Lion tailing” is a form of pruning that removes branches from the interior of a tree leaving tufts of foliage at the ends of branches. This kind of pruning is destructive to oak trees as it lets too much light permeate the crown of the tree
Plants don’t want to be pruned! The first point is that no plant wants to be pruned. Gardeners prune plants because they think it is necessary for horticultural, aesthetic or safety purposes. Gardeners should temper their pruning by understanding plant responses that result from pruning. Generally plants don’t respond much when dead portions are pruned away. In some cases removing large dead portions of a plant will allow more light to enter and some response can occur, e.g., damage to portions of a plant not used to such sunlight intensity. So even a dead plant part may be doing something that you don’t understand. Also dead wood or dead plant parts may be part of some other organism’s home. Owls and other birds nest in cavities, some kinds of bumble bees will reproduce in old flower stalks of desert plants such as Nolina, etc. So dead plant parts are not always useless. If you are pretty sure that nobody else is using dead material go ahead and remove it if bothers your garden aesthetic.
This Ancient sycamore is falling apart with dead wood as younger stems continue to grow. The deadwood provides habitat for animals and in this location poses no risk to people so there is little reason to remove it.
There are two physiological responses to pruning
The two principles of pruning can be used to train plants and in the case of trees, produce a strong architecture that will not easily fail (drop branches). To achieve pruning goals two kinds of pruning cuts are used: the heading cut and the thinning cut. Heading cuts are often made in the middle of stems and do not have a branch that can take over the terminal role of the removed portion. Heading cuts are often used to reduce size or volume of plants. Thinning cuts remove branches at their origin. If thinning cuts are not too large and don’t allow excessive light into a canopy the plant will not respond by invigorating buds. Thinning cuts are used to maintain the natural form of a plant but can be overdone. Over-thinning results in plants that have so much light now entering that buds are invigorated and new shoot form in overwhelming and unnatural locations just as when heading cuts are made. Excessive use of thinning cuts can also produce trees that are “lion-tailed” where all the leaves occur at the end of Pom Pom branches. Remember from a tree or shrub point of view they don’t need or want to be pruned.
A thinning cut removes a branch at its attachment.A heading cut removes a branch or stem without a side branch to assume its dominant role in the plant
Back to plant responses. There are two responses that most plants have to pruning. When living portions are pruned the remaining portions are then invigorated. This implies that dormant or “latent” buds will grow that would not ordinarily grow so plants will produce flowers or foliage in new places. In this way we can re-direct the growth of plants to achieve pruning goals we may have. This is how we can pleach a tree to grow flat along a wall or produce topiary shapes with shrubs. These kinds of pruning that dramatically alter form of a plant will require successive and significant pruning to maintain the altered form or shape. Not all plants can tolerate this and even those that do can be subject to sunburn or other processes that cause them injury. The second common response to pruning is that the more a plant is pruned, the less it will grow—pruning is a growth reducing practice. Even though buds are invigorated through pruning they can’t make up for the lost leaves and buds taken away without utilizing stored energy. The overall effect of having leaves removed is to slow the growth of the entire plant. Pruning when used as high art results in Bonsai plants that are really stunted individuals with highly stylized forms.
These plane trees along lake Como in Italy have been pollarded to dwarf them. Removing branches each year stunts the tree and limits its growth in a sustainable way. Pollarding is a style of pruning that requires continued removal of branches each year.
Pruning devigorates plants
Since pruning removes leaves and buds (which make more leaves) it is a devigorating process. You are taking away a plant’s ability to harvest light energy and convert carbon dioxide and water to sugar. All this happens in leaves. The fewer leaves a plant has the less sugar it can accumulate and then the less work it can do in terms of growing. On old or slow growing plants pruning removes energy needed for growth and also the energy needed to make secondary metabolites or chemicals which fight insect and pathogen attacks. This is why old trees pruned hard often died not soon after or become susceptible to pathogens they may have been able to fight before the pruning happened. Whenever you prune something think about how you are taking away photosynthate and what it might mean to the plant.
Fruit Trees and Roses
We have to prune fruit trees to make them fruitful? NO. Fruit trees produce lots of fruit when they are not pruned. The goal of pruning fruit trees is to modify trees so fruit is: • in an easy to pick location, • so there is less of it • and so the fruit that forms is of higher quality. An unpruned tree will make the most fruit but it may not be the quality or size you desire or where you want it in terms of picking height.
The same goes for roses. There are many pruning schemes for roses, but the most flowers will be found on the least pruned shrubs. Flower size is mostly determined by genetics. Shrubs that are severely pruned will have fewer flowers than their unpruned counterparts.
Roses have may pruning paradigms but the basic rules of pruning apply the more you prune it the less it will grow. The less you prune it the more flowers you will have.
Pruning and Disease
Pruning to remove diseased parts is often cited as a common garden practice. With some diseases like cankers and blights it is a good idea to prune out infected portions before they make spores or other inoculum to further infect the rest of the plant. In most cases it is important to prune well beyond the diseased portion so all of an infection is removed. Some diseases are “systemic” such as wilt diseases and while pruning will remove a dying portion it will not rid the plant of the infection. It is always best to identify the cause of disease even before pruning it from the plant. As we will learn in an upcoming blog I rarely recommend sterilizing your pruning equipment with disinfectants. A stiff brush and water is all that is needed when removing most diseased plant parts.
Pruning is a useful tool for gardeners. To get the most from the practice it should be conducted with knowledge of the effects it will have on the plant that is being pruned. This is quite variable and in some cases pruning is really contraindicated. While some plants like herbaceous perennials will be pruned to the ground either by the gardener or by frost, others maintain above ground architecture and pruning choices make permanent impact to many woody plants. In the next blog I will write about pruning young trees to create strong structure.
This Maten tree (Maytenus boaria) has a canker disease. A good reason to prune out branches, but in this case pruning may have been delayed too long as the tree will be quite disfigured after removing all the affected branches.
References:
Downer, J., Uchida, J.Y., Elliot, M., and D.R. Hodel. 2009. Lethal palm diseases common in the United States. HortTechnology: 19:710-716.
Downer, A.J., A.D. Howell, and J. Karlik. 2015. Effect of pruning on eight landscape rose cultivars grown outdoors Acta Horticulturae 1064:253-255
Chalker-Scott, L. and A. J. Downer. 2018. Garden myth busting for Extension Educators: Reviewing the Literature on Landscape Trees. J. of the NACAA 11(2). https://www.nacaa.com/journal/index.php?jid=885
“Chemical-free” – a term I’ve seen several times attributed to many products, especially food and produce at farmers markets and even in gardening circles these days. This term is often misused to describe plants grown without the use of any pesticide, either conventional or organic. I have my thoughts that I’ll share later on that subject but first let’s talk about this “chemical-free” that gardeners, farmers, and others use and why its not only a myth, but a dangerous one at that.
Ain’t such a thing as “chemical-free” anything
At face value, the term “chemical-free” would literally mean that whatever the label is applied to contains no chemicals. That the entire item, whether it be animal, vegetable, or mineral is devoid of any and all chemicals. Factually this can never, ever be true. Everything that exists is made of chemicals. Oxygen, water, carbon dioxide, and any simple molecule, by definition, is a chemical. Plants and animals are organized structures filled with complex chemicals. Even you and I, as humans, are walking, talking bags of chemicals. The air we breathe, the food we eat, and the water we drink are all composed of a great mixture of chemicals. The use of the term “chemical-free” to describe anything is uninformed at best, and intellectually dishonest at worst. But a bigger problem, as we’ll discuss later, is that using the term can cause confusion and even fear of things as simple as food and as complex as science and medicine.
What most people intend to say when they use the term “chemical-free”
in relation to plants or produce is that they are produced without use of
pesticides or conventional “chemical” fertilizers. Therefore, a better term to use would be “pesticide-free”
instead of “chemical-free” as it more accurately represents the situation. Many may ask why the term “organic” or “organically
grown” couldn’t also be used to describe “pesticide-free” plants. And while those terms would be accurate, organic
production can involve the use of organic pesticides that are derived from
natural sources such as plants, bacteria, or natural minerals. Natural sources of fertility for plants, such
as composts and even soil itself, are all composed of a myriad of chemical
substances. Plants don’t differentiate
between the chemicals they uptake from compost or soil and those from
fertilizers. To plants, nitrogen is
nitrogen and phosphorous is phosphorous no matter where it comes from.
For some clarification on what different growing and production terms like these mean, check out this lecture I gave for the Oregon Farmers Market Association earlier this year.
While many have a strong opinion on the use of pesticides and fertilizers, I’ll state here that the use of any pesticide, organic or conventional, must follow the label on the container by law. And the use of any pesticide according to the label instructions means that the use of that pesticide should present a minimal risk to the health of the applicator, consumer, off-target species, and the environment. And don’t use any home remedy recipes or products that aren’t labeled (or at least scientifically researched) for use as a pesticide. In most cases these remedies aren’t effective, in some cases they can be more dangerous to human health or the environment than the pesticide they are trying to replace. And applying them as a pesticide could also be illegal.
Pesticide label signal words that denote relative toxicity of a given pesticide.
Any gardener or producer, whether they use pesticides or not, should also be practicing Integrated Pest Management (IPM) to decrease or mitigate the effects of insect and disease pests on their plants. For those using pesticides, use of the least toxic pesticide that offers control of the problem should be the last step in a series of steps to avoid damage from pests after a threshold of damage has been reached. For those who don’t use pesticides, IPM should be a central practice in their gardening or farming practice. Unfortunately, the tradeoff for not using pesticides is often time and labor, so successful “pesticide-free” growing often involves more work (and for produce at the market or grocery store, a higher price). I have seen some gardeners and farmers who don’t use pesticides and don’t make an effort to practice IPM, taking whatever plants or produce mother nature and her children deal them. I’ve sometimes referred to this type of growing as “organic by neglect” as I see insect and disease riddled produce harvested and even sold at local farmers markets.
Why does it matter?
“So what if I use the term ‘chemical-free’? It doesn’t hurt anyone,” you may say. While this may seem the case, the use of the
term “chemical-free” has risen as a result of what many call chemophobia,
effects that reach far beyond the garden or the farmers market. This kind of thinking leads to the incorrect
notion that all “natural” remedies are safe and all “synthetic” remedies are
dangerous. True, many chemicals do pose
a risk to human, plant, animal, and environmental health but many do not. Just like not all natural substances are safe. Poison ivy, anthrax, botulinum, and cyanide
are all natural and cause everything from a skin rash to instant death
(sometimes I get poison ivy so bad I wish for instant death).
This chemophobia can lead to, or is a symptom of, a broader mistrust of science, the scientific process, and modern medicine that has developed in society in the last few decades. Many attribute this to an anti-intellectual or anti-science stance in society resulting from mistrust or political saber-rattling against universities, education in general, science/scientists, “big Pharma”, “big Agriculture”, and others. As a result, the news is filled with people who eschew well-researched scientific advances that have been proven safe and instead turn to home remedies that have no such guarantee of either effectiveness or safety. The results can be worse than the effects of the proven advance the person was trying to avoid.
While the outcomes of “chemical free” gardening might not
have such dire consequences as immediate death, the misuse of such terms can
feed into a cycle of anti-science cause and effect, serving as both a cause and
a symptom of mistrust of science and the scientific process. While everyone has a right to choose whether
or not they use pesticides (or any other scientific advancement), making such
decisions from a place of knowledge instead of fear is paramount for success
and continued advancement.
With drought conditions or lower than average precipitation becoming more widespread across the country, it’s time to revisit the principles of xeriscape gardening. Let’s take a look at the “classic” principles and we’ll update them, Garden Professor style. Note: If you’re growing food crops to supply your table not all of these principles will apply. Some will, e.g mulching, and some won’t. This blog post is focused on ornamental landscaping.
James Steakley/Creative Commons
SO WHERE DID IT ALL BEGIN?
As an “official” landscaping technique xeriscaping seems to have begun in the early 80’s. Denver Water, the largest and oldest public water utility in Denver, Colorado, coined the term xeriscape in 1981 by combining “landscape” with the Greek prefix xero-, meaning ‘dry’. The utility then began to formally define the main principles of xeriscaping for members of the Denver community interested in modifying gardening practices to save water. The results were the Seven Principles of Xeriscaping, listed below.
THE SEVEN PRINCIPLES OF XERISCAPING 1. Sound landscape planning and design. 2. Limitation of turf/lawn to appropriate, functional areas. 3. Use of water efficient plants. 4. Efficient irrigation. 5. Soil amendments. 6. Use of mulches. 7. Appropriate landscape maintenance.
Let’s review them and apply some up-to-date gardening information.
1. “Sound landscape planning and design” – the ideal starting point for all gardens, “Right Plant, Right Place.” This principle earns a GP thumbs-up.
2. “Limitation of turf/lawn to appropriate, functional areas” – turf has a place in the landscape but perhaps not everywhere or in every landscape. “Right Plant, Right Place” (hmm, that sounds familiar). Another GP thumbs-up.
CC
3. “Use of water efficient plants” – it may be stating the obvious but you want water efficient plants that work in your grow zone or micro-climate. Do some homework and choose plants that will be happy in your region. We’ll give this one a GP “OK” with a few points lost for being vague.
Photo by Halawa Xeriscape Garden
4. “Efficient irrigation” – this one has always been a puzzler. Perhaps it was included for folks who can’t break the habit of watering their gardens. The goal of xeriscaping is to have a landscape that does well on the average precipitation of an area. Granted in times of drought some plants may need a good drink now and then and new plants may need help getting established. But for the most part watering should be at a minimum and at the correct time, seasonally as well as weekly or monthly. Don’t forget to include any natural slope and drainage in your efficient irrigation plan. And “efficient” includes a correctly working automated system if you use one. This gets a GP “OK” as well.
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5. “Soil amendments” – We now know that amending the soil is not a recommended practice. It interferes with drainage, causes soil subsidence and is not conducive to root growth. Plants need to be planted in native soil, whatever it may be. This one gets a big “F” for Fail and shall be removed from our list.
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6. “Use of mulches” – if you’ve been following the Garden Professors blog you’ll know this is a winner. You also know that, ideally, we recommend using arborist chips but we also know that not everyone has access to them. Mulch choice also depends on the landscape site, plant choice and, in many instances, local codes. An organic mulch (but not bark) is usually the best bet, but there are times when an inorganic rock mulch is desirable. Do your homework and choose the best mulch for your situation. Mulch! This xeriscape principal gets the GP Seal of Approval.
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7. “Appropriate landscape maintenance” – too often xeriscapes are advertised as “maintenance free”; this is false. Like all landscapes and gardens xeriscapes are an artificial environment and require maintenance to thrive. Established xeriscapes will, hopefully, need less maintenance but they do need care. This can include dealing with weeds, regular inspection and maintenance of an irrigation system, and regular plant husbandry items such as pruning and clean up. This gets a GP thumbs-up.
Image by Leubert/Creative Commons
So, based on the above discussion, here are The Garden Professor’s Principals of Xeriscape, Revised Version
THE SIX PRINCIPLES OF XERISCAPING 1. Sound landscape planning and design. 2. Limitation of turf/lawn to appropriate, functional areas. 3. Use of water efficient plants. 4. Efficient irrigation. 5. Use of mulches. 6. Appropriate landscape maintenance.
Looking over these principles we see no reason why they can’t be applied in every region and in every landscape. Learning to garden with what you have and where you are is the hallmark of a wise gardener. Garden smarter, not harder.
In the past week, two new major climate reports have been released. One is the latest (6th) report from the Intergovernmental Panel on Climate Change (IPCC) and the other is the State of the Climate 2020 report. Of the two, the IPCC report has garnered a lot more press, but both are compilations of work by hundreds of scientists looking at recent weather and climate patterns and how they are affecting us here on earth. The IPCC report also provides projections of what the future climate might be like, using a number of assumptions about how the earth behaves, which can be difficult, and how humans respond, which is arguably even tougher to determine. In this post, there is no way that I can cover both sets of reports in meaningful detail and I won’t address how we need to address the rapidly changing climate here, but I do want to try to pull out some things that you can use as gardeners now. {Note, the pictures are ones I have taken myself on recent trips to use as eye candy!}
What do the new reports tell us?
The State of the Climate 2020 report, published jointly by NOAA and the American Meteorological Society, focuses on global climate events that happened in 2020. You can read some of the notable findings from the report at my blog. The report also discusses many of the “big” climate events of 2020 and puts them into historical context, including how frequently these extreme events occur and how the changing climate is making them more likely.
The United Nations’ IPCC 6th Assessment Report presents similar information but also makes more explicit the cause of the warming, which scientists have known for well over 100 years has been caused primarily by human emissions of greenhouse gases in the atmosphere that trap heat near the earth’s surface. The IPCC report makes it clear that the rapid pace of the warming will cause severe changes to the earth’s climate that will be difficult for humans and ecosystems to adapt to.
What do the conclusions of these reports mean for gardeners?
Here are some of the changes that we will
have to adapt to in the future:
Rising temperatures across the globe—Temperatures are rising across nearly all the globe, both on land and in the oceans. Warmer temperatures mean warmer winters, hotter summers, and longer growing seasons. They also mean more increases in both evaporation from water surfaces and more evapotranspiration from plants, resulting in increases in water stress. That means you may need to water more often or use other techniques like mulch to preserve soil moisture. You may also need to switch to more heat-tolerant species as the USDA plant hardiness zones shift north (in the Northern Hemisphere). It may become harder to work in the middle of the day when it is the hottest.
Rising temperature leads to rising humidity levels, at least where there is a source of water vapor nearby. The higher humidity is contributing to higher night-time temperatures, which puts stress on animals living outdoors (pets, livestock, and wildlife) and also stresses some plant species. It can also lead to more clouds, which reduce direct sunlight and cool the air but also reduce solar radiation available for plants, slowing their development. You may have to manage your gardens for more diseases that are related to the high humidity levels.
Some areas like the northern US may see more rain, while others like the Southwest become increasingly dry. Year-to-year variability in precipitation is also likely to increase, with both more floods and more droughts. In both cases, water management of your gardens will become increasingly important, with the heavy rain events causing more erosion and the potential for loss of plants and trees from too much water and not enough air in the soil, and the longer dry spells making gardens more dependent on either drought-tolerant species or more frequent irrigation. You may have to put in rain gardens to help slow the movement of water through your gardens in heavy rain.
With the rising temperatures, frost and snow will become less likely but will still occur (there will still be winter!). This will allow you plant earlier than in previous decades but will still make the plants vulnerable to late-season frosts.
Increases in carbon dioxide may provide some fertilization of some plants, but only if there is enough water available for growth. Since some weedy species are more efficient at using carbon dioxide than other plants, you may need to deal with more weeds and invasive species in the future than you do now.
Strong storms like hurricanes and derechos may occur more often and be more damaging than the ones we are already seeing now. The research in this area is less definitive than that for rising temperatures because there are many different factors that go into storm development, but scientists generally agree that the number of hurricanes seems to be climbing upward and that the seasons are getting longer. In addition, the storms appear to be moving slower, and that is likely to lead to more rain from the storms over a specific area and more likelihood of rapid storm development. If you live in an area that is prone to strong thunderstorms or tropical cyclones, you may see them more often and the season may start earlier in the year. Rains and winds are likely to increase, leading to more tree damage and flattened plants.
Will we be able to see these changes over the next few years?
Year-to-year variations in climate will continue to plague gardeners, since whatever happened last year is unlikely to occur again this year. The climate naturally varies over time and space as well as exhibits these long-term changes. That means it can be hard to see the creeping trends in temperature and precipitation in the noise of yearly climate swings. If you are only worried about next year’s garden, what is happening in 50 years may not be of much interest. But if you care about your children’s gardens and their future on a warmer earth, than it is something these two reports make clear we have to think about and do something about.
Personal note: This week I was also invited to participate as an author on another upcoming large climate report, this one the 5th National Climate Assessment (NCA) that focuses on changing climate in the United States. I will be one of a number of authors contributing to the chapter on the Southeast US. If you are interested in what the content of that report includes, you can view the 4th National Climate Assessment, released in November 2018. There are chapters for each section of the country, but also chapters that deal with economic sectors like water and agriculture. The 5th NCA will update the information in the previous version as well as add additional information based on scientific studies completed since then.
References:
The State of the Climate report in a peer-reviewed series published annually as a special supplement to the Bulletin of the American Meteorological Society. The journal makes the full report openly available online, here. NCEI’s high-level overview report is also available online, here.
Sixth Assessment Report, Climate Change
2021: The Physical Science Basis is now out. The report
addresses the most up-to-date physical understanding of the climate system and
climate change, bringing together the latest advances in climate science, and
combining multiple lines of evidence from paleoclimate, observations, process
understanding, and global and regional climate simulations. Get more
information including links to the press release and some videos here.
This home landscape is managed using science-based methods; the only routine additions are water and arborist chip mulches.
Upon reading this post’s title, you may be inclined to stop right there. (That’s why I have an eye-catching photo to lure you in.) While logic may seem irrelevant to your enjoyment of gardening, I can guarantee that reading this blog post will challenge many seemingly logical assumptions you’ve heard or read about. Recognizing unsubstantiated assumptions and avoiding their pitfalls means you can make wise choices about how you care for your gardens and landscapes.
You can find this and thousands of other silly correlations at www.tylervigen.com
A few definitions are needed before we get started:
Correlation refers to variables whose changes mirror one another. For instance, the addition of nitrogen fertilizer to container plants is correlated to plant growth: as nitrogen levels increase so does plant growth. You can also have inverse correlation, where the variables move in opposite directions. An example is water availability in soil and planting density: the more plants you have in a specified area, the less water is in the soil.
Plant growth is correlated with increased nitrogen and other nutrients (from Xu et al. 2020)
Causation takes correlation one step further: it establishes that one of those variables is causing the change in the other. Using the same examples, we know through published evidence that the increase in nitrogen is causing the increase in plant growth, and the increase in planting density is causing the decrease in soil water because of competing roots. These relationships are obvious to us, but what’s important is that these causative effects have been established through scientific experiments.
Inverse relationship between planting density and soil water content (from Shao et al. 2018)
Sometimes scientific evidence doesn’t exist to demonstrate causation. That may be because it’s impractical or impossible to run an experiment that tests for a causative effect, or it may be because the experiments just haven’t been conducted yet. The latter is the unfortunate reality for those of us interested in managing gardens and landscapes: there is no major funding agency that supports field research for us. There is research being done, but it’s on a small scale with a shoestring budget…so the body of literature develops very slowly. In such situations, we must rely on established applied plant physiology and soil science to ask whether a suggested correlation might be elevated to causation.
Something caused these arborvitae to fail…but what? Research is slow to catch up to our observations of landscape failures.
Which brings me to my current source of online irritation: the constant blaming of tree failure on mulch volcanoes. Yes, tree failure is definitely correlated with mulch volcanoes – because lots and lots of newly planted trees fail. But is the mulch to blame? No one seems to care much that there is NO published work to show that mounds of appropriate mulch materials will somehow kill otherwise healthy trees. Instead, observers jump to the conclusion that thick layers of wood chip mulch kill trees. They are elevating correlation to causation in the absence of either experimental research OR known plant physiology. In fact, there is published research to show that thick layers of arborist wood chip mulch enhance tree establishment and survival. And there are many poor planting practices that increase the likelihood of tree failure. But it’s easiest to blame the wood chip mulch, though it’s merely masking a multitude of planting sins.
Street volcano 1
Street volcano 2
Volcano as garden fashion statement
Volcano mulching is ugly – but does it cause tree failure? Or is it hiding something?
Not interested in mulch volcanoes? Well, there are lots of other examples of garden and landscape management practices or phenomena that fall into the logical fallacy camp. I’ve linked to appropriate references, when available, that go into more detail:
and just about any gardening product you can think of where there is NO published evidence – or appropriate, established plant or soil science – that supports any causative, beneficial effect on plants or soils. Cornmeal, Epsom salt, gypsum, and kelp products are just some of these.
All of these products, practices or phenomena are correlated with some anecdotal observation (increased yield, healthier soil, plant failure, etc.) that elevates them to causative relationships. But no science.
I’d encourage you to think objectively about your closely held beliefs about your gardens or landscapes. Are you sure that what you’re doing is actually beneficial? How do you know there’s a cause-and-effect relationship? I’m not going to talk you out of your cherished beliefs – but if you are a science-based gardener, you might talk yourself out of them instead.
Willow screams in pain What is its source of anguish? More research needed!
