I received an email this week from an arborist colleague who had been sent an “engineering solution” which claims to help with rooting issues in clayey soils or areas where root area is reduced. There was a spiffy diagram accompanying this which I’ve reproduced below.
I could dissect this for you and point out all the problems right now, but instead I’d rather supply you with some factual information and let you apply it to this “engineering solution.”
Planting hole material that is not the same as the surrounding soil will have reduced water, air, and root movement due to the abrupt changes in texture. The hatched material in the pit appears to be different from the surrounding soil, leading to the assumption we’ve got modified backfill. Here’s a peer-reviewed journal article that discusses the fallacy of soil amendment.
“Augured sump drain/root channel bores” are simply modified French drains. French drains serve to move free water (i.e., water that is not in soil pores) somewhere. Where “somewhere” is in this case is unclear.
French drains and other drainage systems do NOT reduce the amount of water that soil holds. Field capacity is the term used to describe a saturated soil. A sandy soil has a low field capacity and drains quickly. The higher the clay content of a soil, the higher the field capacity and the slower the drainage.
“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.
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.
Now that much of the world’s attention is focused on
limiting the spread of pathogens, well one pathogen, it seems like a good time
to talk about some of the questions or concerns we’ve seen regarding vegetable
gardens, community gardens, and farmers markets. It’s a good time to talk about some of the
practices that we should be doing to prevent other human pathogens from
handling produce, like E. coli and Salmonella, and how those might fit into
preventing the spread of COVID-19.
First things first
First off, we have to remember that SARS-CoV-2, which is the virus that causes COVID-19, is not a food borne illness. I repeat: COVID-19 IS NOT A FOOD BORNE ILLNESS. This means that it is not spread through the consumption of contaminated food like E. coli and Salmonella. I’ve seen many instances of people spreading fear about food online, with many suggesting using soap or bleach on food to minimize risk. Those steps are both unnecessary an actually pose a poisoning risk. There is currently no evidence to suggest that COVID-19 is transmittable by food or food packaging.
The risk from food (which is considered minimal by experts)
is from cross-contamination from food or packaging onto hands or onto surfaces
that are then touched by hands. The
virus would then have to go from a persons hand to mucous membranes in the
respiratory system by something like touching your face or picking your…..well,
we won’t go there. The best defense
against this isn’t necessarily sanitizing all the food you buy, but washing
your hands after you handle it and sanitizing any surfaces that packaging or
shopping bags touch.
But while we’re on the topic of pathogens and food safety,
it’s a good time to talk about some general guidelines that can not only help
stop that potential SARS-CoV-2 cross contamination but also food borne illness
Minimizing the risk from produce even further
Whether you grow it in your own garden, buy it at a local
farmers market, or purchase it at the grocery store, produce has a minimal risk
when it comes to COVID-19.
To minimize the very small risk of cross-contamination even further and (probably more importantly) to also reduce any risk from common food borne illnesses, proper washing of the produce should be practiced. But do you know how to do that? Maybe…and maybe not. Here are some steps to help out.
Wash your hands. The most common pathway of contamination for produce is from human touch.
You should use clean water that you would use for drinking (like out of the tap) and not use any bleach or soap.
Providing gentle friction with your hands or a produce brush or by rubbing the produce together is sufficient.
If you’re washing a lot of produce at once, say from a large harvest, and you’re using a tub full or sink full of water to wash multiple “loads” of produce, keep an eye on how dirty the water gets and refresh it when it gets discolored. Remember that washing produce in a tub or sink of water can also present a cross-contamination issue where contaminated produce contaminates the water.
When in doubt, discard produce you may think is contaminated or wash it separately.
To reduce risk of cross-contamination, consider a “single pass” washing technique where you spray the produce with water and it doesn’t sit in water with other produce.
Food Safety in the Garden
There are a few things we can do in the garden to help stop
the spread of human pathogens. Most of
them are common sense things that most people don’t even think about. Devout GP readers may remember my little
missive around this time last year about the food safety risks of using manure
in the vegetable garden (See: The
Scoop on Poop). Beyond those musings
on manure, though, gardeners can take some additional steps to reduce potential
contamination. Those are:
Wash your hands.
I know it sounds simple, and maybe even more so now that it has been
drilled into our brains, but washing your hands before you garden is one of the
best ways to reduce the spread of pathogens.
It is especially important to wash your hands before you harvest produce
or handle harvested produce.
Use clean containers for collecting and storing
produce. Using harvest baskets, tubs,
and totes is common, but the ones that are best in terms of food safety are
those that can be washed and sanitized.
This is one tactic that many farmers are encouraged to use as well. Plastic tubs, totes, trugs, and crates are
probably best as they can withstand washing and the use of a sanitizer like
bleach. Wooden or woven baskets may be
cute, but they’re harder to clean and can hold on to pathogens.
Look for signs of wildlife in the garden. Aside from eating more than their fair share
of produce, wild animals can also present a food safety risk especially from
their droppings. Look for signs of
animals in the garden and especially take note of any droppings. Don’t harvest produce that has signs of
droppings on them. Many of the big
produce recalls over the last decade have been a result of wild animals like
birds or wild hogs.
Keep pets out of the garden. As much as you like to have Fluffy or Fido in
the garden, they present a risk just like wild animals do.
Wash produce using proper techniques (previously
Best practices for minimizing COVID-19 risks at Community
Gardens (and Farmers Markets)
One other aspect of gardening that could provide some risks for the spread of COVID-19 are the more social aspects of gardening, such as community gardens. I’ve had several local gardens reach out for best practices relating to minimizing risks in the garden – from handwashing stations to shared tool use. Thankfully, NCSU Extension was quick on the draw with resources for lots of aspects of the food system in terms of reducing risks from COVID-19 and they graciously allowed other universities to distribute these resources. Below are some links to the resources that would be helpful to gardeners:
This isn’t the first time I’ve ranted about bad mulch choices and it certainly won’t be the last. But this pictorial cautionary tale is too important to pass up.
We already know that sheet mulches can be death to microbes, plant roots and animals living in the soil underneath. Our newly published research shows that landscape fabric reduces carbon dioxide movement between the soil and atmosphere about 1,000 times more than wood chip mulches do: plastic mulches are even worse. Oxygen movement will be likewise affected. And while gaps and holes in these barriers can lessen the impact, the question remains: why would you use ANY mulch that reduces gas movement? Yet people persist in using fabrics and plastics, usually to “smother” weeds (and that verb should set off alarm bells for anyone thinking about collateral damage to soil life). But weeds are weeds for a reason, and they will eventually colonize the surface of sheet mulches as soil, organic matter, and water collect over time.
So without further ado, here is a case study of what happens when sheet mulch is used for landscape weed control.
These irrigated landscape beds are in Wenatchee, Washington, which has hot, dry summers. As you can see, bark mulch has been used to hide the shame of sheet mulching. And from a distance it looks…okay.
Upon closer inspection, you can see the shroud of death emerging from the bark mulch (which has no means of staying in place, especially on a slope).
And even close you can see the soil that’s blown in, along with the bark and other organic matter. Just add water, and you get weeds!
Weeds, weeds, weeds! Lots of weeds. Sunny weeds!
And shady weeds!
The weeds are thriving – but the trees are not. The crowns are dying…
…and the trunks are suckering.
But you’ll note that the trees in the first photo outside of the beds are thriving.
And it’s all because of that “weed control fabric.” Which is working so well that this landscape had to be treated with herbicide the day I was there – to control the weeds.
One of the “advantages” of being in the same office suite as me is hearing (a) that arborist wood chips are about as close to a miracle product as you can get and (b) that landscape fabric is hell on (the) earth. So my office mate Liz, either because she was convinced of the above or just wanted to shut me up, decided to rip out the landscape fabric in her ornamental bed and replace it with wood chips. She even made it a family project, somehow convincing her two young daughters that this was “fun.” Here’s her pictorial essay of the process.
Before the switch
Why on earth does anyone still believe that “weed block” fabric actually does anything remotely related to controlling weeds? It provides a great substrate for all those weed seeds blowing around, which find themselves the recipients of any rainfall or irrigation. They germinate and grow like crazy – because they are WEEDS. It’s what they do.
Worse yet for the soil – all of those pores in the fabric that supposedly allow water and oxygen to move through are soon filled with bits of soil. The resulting mat is anything but permeable. But weeds love it!
First Liz had to score some woodchips, which as you can see pretty much filled her driveway. The girls, however, thought they were a great addition.
Next, all of that fabric had to come out. This is not an easy process, because the surface of the fabric was completely colonized by weeds. A mattock is a great tool for getting this done.
Now, let’s look at the soil underneath the fabric. You can see how dry it is. That’s because even during our rainy springs in the Pacific Northwest all of the rainfall stays on top of the fabric, allowing lush weed growth. The roots of all of the landscape plants get virtually none of this, and in the summer that’s a source of chronic drought stress.
Fortunately, the soil underneath, while dry, looks pretty good. Once the shrubs and perennials are able to take advantage of the increased water and oxygen they will thrive.
Maybe you don’t like the look of arborist wood chips, but it’s certainly better than the weedy mess that used to be there. Plus, the soil benefits from the increased water and oxygen, the beneficial microbes in the wood chips, and the slow feed of nutrients as those chips slowly decompose.
If you are ready to switch from “fabric fail” to “wood-chip win,” you can start with this fact sheet which will guide you through the process.
In my educational seminars I’ve long shared a version of the CRAAP test (currency, relevance, authority, accuracy, and purpose) for analyzing information related to gardens and landscapes. My version is CRAP (credibility, relevance, accuracy, purpose), and we’ve published an Extension Manual that explains in detail how to apply it. This past week I was at the Philadelphia Flower Show participating in Bartlett’s Tree Care Update panel. Given that the theme of the show was “Flower Power,” I figured that a talk on Magical Mystery Cures was in order. And the 1960’s was the decade where the late Jerry Baker gained prominence as a garden authority – and whose presence is still widely felt nearly 60 years later.
Now, I could spend the rest of the year discussing all of Jerry’s advice, tips, and tonics for gardens – but it’s more useful to determine whether he is a credible source of reliable information. So let’s apply the CRAP test.
C = credibility. What are Jerry’s credentials as a garden expert? It’s easy to find this information from the internet, including the Jerry Baker website. He had no academic training in plant or soil sciences but started his career as an undercover cop who often posed as a landscaper. His books are all popular publications, meaning they have not gone through critical review by experts before publication.
R = relevance. For our purposes, his information is relevant to our focus of managing gardens and landscapes (as opposed to production agriculture, for instance).
A = accuracy. Jerry’s advice is not based on any scientific source. He relies on common-sense approaches, folklore, and his grandmother’s advice. In fact, many of his assertions are at odds with published scientific evidence. Now, science evolves, and older scientific publications are sometimes found to be inaccurate after new information comes to light. If Jerry’s books were meant to be accurate sources of information, they would be updated with new findings as subsequent editions were published. This is what happens with textbooks, for example.
P = purpose. What is Jerry’s ultimate purpose? It’s sales. There’s no way around this conclusion. Over twenty million copies of his books have been sold, and during his career he became the spokesperson for several gardening products. Probably the most well-known of these was the Garden Weasel (which parenthetically is a great way to destroy fine roots and soil structure). There’s no doubt he was a brilliant self-promoter and marketer. But he was not a reliable resource, and many of his “tips and tonics” are extraordinarily harmful to plants, pets, and the environment.
While I was wrapping up my research on Jerry Baker I was particularly taken by a chapter in one of his books (one of his Back to Nature Almanacs) called “The Tree Quacks.” I thought some of these quotes were particularly ironic:
Imagine my surprise when I discovered that these quotes were actually not his own. In fact, the entire chapter was plagiarized from a 1964 article by John Haller in Popular Science, which is online. This action is uncomfortably similar to his 1985 trademarking of the phrase “America’s Master Gardener,” 12 years after the Master Gardener program was formed (but not trademarked) at Washington State University.
I hope this post has helped you learn to analyze the credibility of information and information sources. If so, you can claim the of America’s Master CRAPper ™!
As many of you know, the Garden Professors host a Facebook group dedicated to the discussion of science-based practices for gardens and landscapes. (Side note – if you haven’t joined us please do!) Recently we’ve had a spate of “what’s wrong with my plant” posts, usually focusing on some leaf issue and little other information. And far too often an eager group member will jump in with a fertilizer recommendation. So today’s blog post has two objectives: explaining why you can’t reliably diagnose problems from a picture of suffering leaves and why blanket fertilizer recommendations should be avoided.
To illustrate the problem with armchair diagnosis, consider this photo below.
Now there are two ways to ask a question here: the first is “what’s wrong with these leaves” and the second is “what’s wrong with my plant.” We can easily answer the first one: there is nutrient deficiency in the leaves, most probably iron or manganese. But that does NOT mean there is a deficiency in the soil. So we can’t address “what’s wrong with my plant” because we don’t have enough information.
How can we determine what’s wrong? My first question to the poster is invariably “have you had a soil test?” Soil test results will indicate whether the element in question is actually deficient, and will provide levels of other nutrients that could interfere with root uptake. If there’s no deficiency of the nutrient in question, then adding fertilizer is not going to help! And adding fertilizer unnecessarily can create further soil nutrient imbalances and contribute to environmental pollution.
Once we have the soil test results, we can then begin to address “what’s wrong with my plant.” But not from the original picture. (If you are curious about what else could be causing this problem, check out this blog post from 2011.)
Let’s try another. Consider the leaves in this photo:
We now know to ask “what’s wrong with these leaves?” Ignore for now the deficiencies in the older leaves and look at the size of youngest ones compared to the older. The answer is fairly straightforward here: there was too little water available when the newly emerging leaves were expanding. Leaf expansion depends on turgor pressure – the higher the turgor pressure, the larger the leaves get. Once expansion stops, protective plant biochemicals are laid down which prevent further expansion. By comparing the youngest leaves to the leaves from previous years, you can see that they are significantly smaller. But why?
Again, we need more information before we can answer “what’s wrong with my plant.” Was there too little available soil water during leaf expansion? It’s possible, but this example is from western Washington State, a climatic region with wet springs. Most likely there is an issue with the roots. My first question with these cases is “can you easily move the plant in the ground?” This is my “wiggle test” – a way to determine if roots are established. In this case – and in nearly every case like this that I’ve seen personally – the roots are NOT established. Often this is because the plant (1) was not bare-rooted at planting and/or (2) was planted too deeply. Without decent root establishment there is not enough water uptake to support full turgor in expanding leaves.
Lack of an established root system also account for the interveinal chlorosis you can see in the oldest leaves. These leaves are fully expanded, probably because the plant was still at the nursery when these leaves emerged. But their color is off. A root system that doesn’t supply sufficient water for leaf expansion is by default not going to provide sufficient nutrients, either. Adding fertilizer to this plant is not going to help! It needs to be dug up and replanted correctly or replaced. It is never going to thrive under the current conditions.
Armchair diagnosis can be accurate and fun if you follow a set of guidelines to extract more information. But simply recommending a fertilizer based on leaf appearance is neither science-based nor environmentally responsible.
By Jeff Gillman (posted by Linda C-S, who has taken liberties with using photos from UNC Charlotte gardens that have nothing to do with Jeff’s post.)
It has been almost two years since I have had the chance to post anything as a Garden Professor. Since then I’ve taken a job as the Director of UNC Charlotte Botanical Gardens and there are all kinds of things I’d like to share with you, and perhaps sometime over the next few weeks and months I will, but for now what is probably most pertinent is that I absolutely love my job. I am still doing some work on garden myths, but what I’m finding more entertaining is investigating the histories of different plants and their interactions with humans. In fact, in about a month or so, my friend Cindy Proctor and I will be releasing a podcast titled The Plants We Eat that investigates the interesting history, culture and biology of the various plants we use for food. We’ve already recorded shows on strawberries, grapes and mad honey, and we’ll be doing shows on apples, figs, and a few others before we release it – we want to have a decent backlog of shows so that we can maintain a pace of one podcast a week.
But enough about me! The current Gardens Professors called my attention to a recent article titled “The effect of ad hominem attacks on the evaluation of claims promoted by scientists”, and I found it informative to say the least. This article provides instructions on how to stop people from trusting a particular study.
No, seriously. If you wanted to you could actually rewrite this as a short manual on how to make people question the results of any scientific study.
And if you did I think it would look kind of like this:
(Short Disclaimer – I’m pretty sure that the authors of the above article never intended it to be taken in the way I’m presenting it. I’m posting this purely as satire.)
So, someone has published a scientific article that you disagree with. Hey, we’ve all been there. Scientific evidence that contradicts your beliefs/works/preconceived notions sucks, but it isn’t the end of the world. There are things you can do.
You might consider conducting your own well-designed experiments that would call into question some of the claims of the offending work. Once upon a time this was been the standard way to address this kind of problem, but this could take months or even years to accomplish. And the truth of the matter is that your experiment might not even say what you want it to and even if it does, with attention spans the way they are, nobody will even remember what you’re even talking about when your paper comes out.
Which is to say, there are better, faster ways to take care of inconvenient research, and that’s where this convenient manual comes into play.
First, realize that attacking the research itself isn’t a sure thing. Sure, it’s the right thing to do, but morals be damned, attacking the research itself can be waaaayyy too technical. People won’t understand what you’re talking about, so forget about it.
Attacking researchers personally by making nasty comments about where they graduated from college or that they do sloppy research would seem like winner, that kind of attack just doesn’t cut it today. Maybe it’s the political climate, but, to their credit, people just aren’t responding to non-specific personal attacks the way they once did.
So you’ve got to be smart and hit them where it hurts. You could say that data was fabricated in the paper that you want to discredit, but this could be problematic if it isn’t true. Not to worry. All you really need to do is find an instance where the researcher did do something wrong. In fact, it’s possible that some past misconduct could be even more effective at discrediting a paper than misconduct on the paper in question itself.
The gold standard, however, is conflict of interest. By establishing that the researcher who has caused you grief has some sort of conflict of interest you can cause people to question the results of research just about as effectively as if some sort of misconduct had taken place, and conflicts of interest are much easier to find! You could blame a company, a person, or even a University. Shoot, want to show that a study, which demonstrates that an herbicide is effective at controlling a weed, isn’t true? All you need to do is show that the company which makes the herbicide gave a few hundred dollars to an athletic program at the school, or show that one of the student workers in the lab has a second cousin employed by the company. It’s all good.
And so there you have it. The fast, easy way to discredit someone. And remember, just implying things can be as effective as having facts. No need to lie! Good Luck, and remember The Truth is What You Make It!
Here at the Garden Professors we try to focus on sharing the best applied plant and soil science information for gardens and landscapes. But sometimes we get sidetracked by information that is SO bad that we need to share it too. So the purpose of this occasional feature – Worst Gardening Advice – is not to poke fun, but to point out the real hazards to plants, people, and the environment by following scientifically unsound practices.
Without identifying which of my GP colleagues nominated this video, we now present how NOT to fix storm damaged trees.