Plastic grass and organic gardens

One of the best cures for writers’ block for a Garden Professors is to spend a little time in front of the tube watching home gardening shows.  Now, to be sure, there are useful nuggets of information that can be gleamed from an hour or so of gardening or landscaping on HGTV or PBS Create.  But there are moments when I just stare at the TV in disbelief and go, ‘Have these people lost their frickin’ minds?’


A recent case in point, a half-hour gardening show devoted to installing an ‘allergy free’ backyard for a youngster, we’ll call him Billy, with environmental allergies.  Let me state up front I am in no way minimizing the seriousness of environmental and related allergies.  I suffer wicked seasonal allergies (yes, I know, poor career choice) and I have several close friends whose children have severe allergies.  I realize allergies can seriously affect quality of life and, in the cases of some food and insect allergies, can be a matter of life or death.  And I realize that a parent will do just about anything to keep their kid healthy.  Nevertheless, some of the practices promoted on this show strained all manner of credibility.


First, since Billy is allergic to grass, the landscaper replaced all of the grass in the backyard with synthetic turf.  Grass allergies are among the most common allergies but what is it about grass that most people are allergic to?  Pollen.  According the National Institutes of Health just keeping grass mowed is a simple preventative measure to reduce grass pollen.  Synthetic grass may have issues of its own with molds and there are remaining uncertainties regarding the safety of the used-tire derived crumb rubber used in some fake turf.   And if Billy has issues with pollen, I saw a much bigger problem looming like an 800 lb gorilla as the camera panned back from the picture-perfect synthetic lawn: Trees, specifically dozens of oaks and pines in the woodlots beyond the backyard.  I joined the show part way through but the overall landscape looked like the Southeast, perhaps Georgia or the Carolinas.  Even if the fake turf does reduce grass pollen in the back yard, Billy will scarcely notice as a yellow-green cloud of tree pollen envelops his house every spring.


Next, in addition to wanting a place to play, Billy wanted a vegetable garden.  Actually, given Billy’s obvious disinterest during this part of the show I don’t think he was really that interested in vegetables but the producers knew they couldn’t fill a 30 minute show with just fake turf.  Assuming Billy really was into vegetables the solution, of course, was an organic garden.  Why an organic garden is a panacea for allergy sufferers was never explained in the show; apparently pollens and molds don’t hang out in organic gardens.  The choice of vegetables was curious as well.  Billy got to plant squash and watermelons; guess no one bothered to tell Billy that cucurbit allergies are among the most common food allergies for people predisposed to pollen allergies.  For good measure, Billy got to plant some corn – doubt that could ever produce any pollen…


Bottom-line: take the info from the garden shows with a grain of salt and consider the source of the information.  Often times these shows are limited to whatever local source they could dredge up.  Do you really want to rely on a landscape contractor to make decisions about your child’s allergies and health?  Enjoy the shows but keep your skepticism handy and be ready to do some fact checking on your own.

A nifty garden to visit

I missed my regular posting on Wednesday since (1) I’m on vacation and (2) I hadn’t had time to find anything sufficiently worthy of posting.  (Of course I have a compost barrel full of snake oil products I could rant about, but even I get tired of that.  Especially on vacation.)

Note the strategic head placement

But yesterday we visited the Niagara Parks Botanical Gardens just north of Niagara Falls.  We didn’t have nearly enough time to see it all, so I’ll share just one special corner.

The Poison Plant collection isn’t listed on the map, and the only reason I noticed it at first was the giant hogweed (Heracleum mantegassianum), a particularly noxious introduced species, in the center.  Looking closer, I discovered unique signage for these plants.

I think these types of display gardens – poisonous plants, noxious weeds, etc. – are great educational tools.  The trick, of course, is keeping them from setting seed and spreading.  And keeping 15-year-olds out of them.

What About the Corn?

Year after year farmers in the US plants a lot of corn.  A safe estimate is around 80 million acres with another 70 million acres or so going to soybeans.  Corn comes from South America,  soybeans are from East Asia.  When we plant these crops we plant them in such a way that we exclude or, at the very least, limit the ability of native plants to grow.  A safe estimate is that 99 percent of our cropland is planted in non-native species.  I’d like to get your opinions on whether it’s OK for us to go to such efforts to control invasive species like kudzu and buckthorn when, on the flip side, we’re going to so much effort to encourage other species which don’t come from here.

Our visiting Garden Professor and his Kentucky coffeetree

By Dr. Charlie Rohwer

Since my last guest professor submission (buying organic food for health) garnered so much discussion, I thought I’d try to write about a less controversial topic: evolution.  There’s no scientific doubt that’s where plants (well, all species of everything, really) come from, but what got me thinking about it recently was my Kentucky coffeetree.

My wife and I bought our first house a couple years ago, and for the previous 25 years at least, the landscaping had been severely neglected.  Ubiquitous rock mulch on top of plastic, a cherry covered in black knot, and zero space used for any kind of garden, unless you count the 2 sedum suffering under rocks and plastic.  So we made lots of garden space and bought our first tree, a Gymnocladus dioicus.  But as the epithet indicates, Kentucky coffeetree is dioecious.  The plant either has male flowers or female flowers.  We liked the fact this tree will get tall but not spread too wide, tolerate our soil, have interesting bark and leaves, and the winter shade will be fairly sparse, but we didn’t really want to have the big seed pods from the females.  We bought an unsexed plant in 2009 and hoped for the best.  Make no mistake, we were proud parents, regardless of the sex of our newly-planted 7-foot stick.  It flowered this year, with only stamens.  It’s a boy!  But it got me thinking, where and when did its dioecism come from?  It amazed me that I hadn’t considered it before because I actually work with another dioecious plant, hops (Humulus lupulus).

Flowering plants probably started their evolutionary timeline with both male and female parts near each other.  Carpels (female) and stamens (male) are specialized places where male and female gametes (sperm and egg) are made, fused, and the young sporophyte, as a developing embryo, is protected in maternal structures.  Sounds familiar, but as Bert stated in a recent post, we need to strictly avoid teleology.  In fact, though more common in some parts of the world, dioecism is the exception in flowering plant reproduction (<10% of species).  Most flowers you see are hermaphroditic, with both male and female parts together in the same flower.   Dioecism is so dispersed among plant genera, it’s probably evolved many different times, and is thought to arise through a series of evolutionary steps.  For example, in one mechanism, some individuals within a species loose the ability to make pollen (genetically), and some plants within that species can still produce both male and female flowers.  Then selection can act on the two types of plants separately, and at some point, the ability to make female parts disappears in the hermaphroditic line.  But there are different ways to arrive at dioecism that help to explain how it arose multiple times in so many diverse plant lineages.  Genera other than Gymnocladus (a legume) and Humulus (complicated taxonomy, but clearly related to Cannabis) that have evolved to be dioecious include Spinacia (spinach, an amaranth), Pistacia (pistachio, in the cashew family), Asparagus (a monocot), Dioscorea (yam, in the….yam family), and Ginkgo (not even classified as a flowering plant, and not a conifer either!).

Kentucky coffeetree is a legume, but think of every other legume you know and dioecism is the exception, by far.  Pollination and dispersal mechanisms, optimization of reproductive resources, and outcrossing pressure are thought to drive evolution of these species away from hermaphroditic flowers.  Evidently this happened to the Kentucky coffeetree lineage by 50 million years ago.  About 40 percent of the time that flowering plants have existed, Gymnocladus has been dioecious.  That’s 1 million times longer than a 50-year-old person has existed.  Dinosaurs had been extinct for 15 million years or so by the time the Kentucky coffeetree lineage split from other legumes.  Those are numbers we have a hard time grasping because natural processes have been around a lot longer than we have.



Ainsworth, 2000. Boys and girls come out to play: the molecular biology of dioecious plants. Ann. Bot. 86:211–221.

Doyle and Luckow, 2003. The rest of the iceberg. Legume diversity and evolution in a phylogenetic context. Plant Physiology 131:900–910.

Specht and Bartlett, 2009. Flower evolution: the origin and subsequent diversification of the angiosperm flower. Ann. Rev. Ecol. Evol. Syst. 40:217–243.

Friday puzzle solved – better late than never!

I spent yesterday flying from Seattle to Buffalo and didn’t get a chance to post the answer to the puzzle on Friday.  This was an easy one for our readers – the shrub is (was?) a mesquite, and the bushy growth in the photograph is mistletoe (as identified by Bob and seconded by Ginny and Jimbo). 

I am pretty sure this mesquite was dead, as it had been a wet spring and everything was leafing out.  That being said, I didn’t cut into the bark to find out.  If it is dead, that does raise the fascinating question of how the mistletoe can extract water from a dead shrub.  So it’s likely that the mesquite is just slow to leaf out.

This (and other) mistletoes provide food for native birds, and as Jimbo points out they are the perfect dispersal mechanism for the sticky seeds.  There’s a great video of this behavior in the "Secret Life of Plants" by David Attenborough – if you haven’t seen this series, you should.  Amazing.

Thanks, all, for playing – and Peter, your last comment was perfect!

Compost tea…again

My not-fan Justin has emailed me again with some more substantial comments of my criticisms of compost tea.  I’ve posted his email here, along with my responses in a point-counterpoint format:

1.  “Compost teas do vary from batch to batch, the same way galaxies vary.  Without the complexity and biodiversity present in the tea, you might as well just be using water.”

Yes, they do vary, and this is why it is so difficult to conduct replicated and repeatable studies on the efficacy of compost tea.  The comparison to variability in galaxies is really not relevant, nor is it conducive to experimentation.

2.  “Generally speaking though, this can be overcome by the purchase of virtually any microscope capable of achieving 400x field of vision or greater. By looking at what is present in the tea and a little bit of background knowledge, one can make an educated decision as to whether or not it will improve conditions on one’s plants and soil.”

Purchasing a microscope does not overcome variability.  Furthermore, microbial species can’t be reliably identified simply by looking at them under a microscope.  The “little bit of background knowledge” is vague.  What, exactly, will help in making the “educated decision” in whether it will do any good to use it?

3.  “I assume that these steps were not taken in these experiments, because of the generally lacking method in what has been come to be labeled (tobacco science).”

The steps referred to (I assume in point 2) are not useful in assessing efficacy of a product – in other words, demonstrating an effect not seen in the control treatment.  What would be the control?  Not looking under a microscope?  Not having background knowledge?  An experiment requires experimental variables.  I hadn’t heard of  “tobacco science” and had to look it up.  Apparently it’s “science that is skewed or biased, especially toward a particular industry.”  The only industry I see in this discussion is the compost tea industry – and yes, it’s an industry.

4.  “First of all you are trying to disprove compost tea as a foliar pesticide only. You do not do a relatively new science justice by not looking at the wholeness. Any and all foliar applied pesticides are palliative in nature, and symptoms will recur if you do not deal with the source problem. Compost tea (aerated) is to be used in the rhizosphere first, foliage second, and surrounding environment third. If you are not talking about this mode of application, you are not talking about compost tea.”

Compost tea is not a new science.  It is a product.  To demonstrate efficacy of a product requires conducting a controlled experiment in which there are one or a few variables.  It’s not possible for science to look at the “wholeness” of compost tea – it has to be looked at systematically.  Neither is compost tea defined by its mode of application.

I do agree with Justin, however, that symptoms (of disease or whatever) will recur if the underlying problem isn’t addressed.  There are scientifically testable, consistently reliable methods for improving soil health and plant health. At this point, compost tea is not one of them.

5.  “In order to disprove compost tea, you must first explain to the reader how balances of microbial life (bacteria, fungi, protozoa, nematodes, microarthropods, earthworms) are different in various stages of ecological succession. You must describe how the OVERALL HEALTH of any plant depends on how it has evolved to live in the soil conditions in which it is planted. You must describe how human activity effects soil food webs and how soil disturbed or treated with substances toxic to microbial life will move the soil backwards in succession. This will create a soil that favors weeds over crops by reverting the soil to bacterial dominance.”

Disproving any hypothesis (e.g. “compost tea prevents foliar disease) relies upon scientific evidence.  What Justin is asking for is not experimental but explanatory.  (There are several inaccuracies in what he outlines above, but in the interest of sticking to one topic I’m ignoring them.)

6.  “If you are going to debate compost tea you must disprove its ability to create a more fungal soil and inoculate the rhizoshpere with arbuscular mycorrhizae, improving soil born nitrogen. Excuse me, soil born proteins in the form of microbial biomass that are released as ammonium or nitrates in detritus, when consumed by predatory microbes, that are generally found to be lacking in human disturbed soils.”

The first point is incorrect, and is one of the hallmarks of pseudoscience – reversed burden of proof.  It is up to proponents of compost tea – or any other product or practice – to demonstrate efficacy.  (Wikipedia has an excellent overview of the characteristics of pseudoscience.)

7.  “You must prove: that most garden or Ag soils have a stable food web, the food web is not necessary, or that compost tea does not create a more complete food web. You must create a fair experiment (not paid for by cargill) that tests foliar applications on crops planted into a healthy rhizosphere with a complete food web.”

No.  Compost tea proponents must demonstrate that compost tea has an effect.  Period.  (It’s also important to understand that science doesn’t “prove” anything.  It either supports a hypothesis or disproves it.  That’s why scientific inquiry is a dynamic process – you never know when new evidence will lead to a paradigm shift.)

8.  “If you cannot present your findings in this way, you are misleading your readers knowingly. I was raised to classify that as a lie.”

I don’t conduct these compost tea experiments (though I do conduct research in other areas).  Part of my job as an extension educator is to read the scientific literature and translate it for use by nonscientists.  I have posted an extensive bibliography of the compost tea literature on my web site.  If I were either deliberately or accidentally misleading anyone, I would be in serious trouble with my university.  Given that I started my criticism of compost tea on my web site over 10 years ago, it’s likely that the information is not misleading.

Fan mail…NOT!

Below is an email I received this morning.  I’ve apparently made Justin really angry.  So as he’s requested, I’m giving him the chance to debate me.


Who owns you Dr. Linda Chalker-Scott?

You are a cheap mouthpiece and I don’t believe a word that you say. I’d debate you right under the table.
Any day, Lady.

Why don’t you just bring it on sister girl and first describe how vegetation thrived on this planet for millions of years before the phony baloney chemical crap that you use.

Even if your understanding of chemistry and physics is spot on about sprayed on nitrogen being identical to that in nature, it is unsustainable, it leaches, it costs more to the HORTICULTURIST than simple crop rotating methods. These chemicals disrupt the soil FOOD WEB; are you an ecologist? Are you a biologist?

All you are is a tart mouthpiece for the money monsters. This mail probably goes straight to the corporate lawyers that put those ugly lies in your mouth.
Compost can save the world; but you won’t let it, because it won’t pay for your next elective surgery."

So Justin, here’s your chance to air your complaint.  Let me know exactly what I’ve written that you disagree with and I’ll explain my position.  But keep it civil and keep personal comments out of it.