I just had a long conversation with Michele Owens (of Garden Rant fame) about vegetable gardening. This isn’t one of my strong areas, either professionally or personally (I do have containers of herbs, but that’s as far as it goes). But what piqued my curiosity was her revelation that the vegetable gardening is just as full of myths and misinformation as my field of ornamental landscaping.
I’ve ventured into the realm of vegetable garden science now and then, especially in reference to having soil tests done before planting edibles (good!), the use of CCA-treated timbers (bad!), and companion planting (silly!). Beyond that I haven’t given the topic much thought.
(You know who loves you know who!)
So, readers, what gardening practices out there need to be screened through the sieve of science? Jeff and I have both written about many practices and products, but as you know our expertise is more on the ornamental side.
(Forgive my short blog today. I’ve had some kind of chest crud since last Friday and I’m still wiped out.)
Dr. Linda Chalker-Scott has a Ph.D. in Horticulture from Oregon State University and is an ISA certified arborist and an ASCA consulting arborist. She is WSU’s Extension Urban Horticulturist and a Professor in the Department of Horticulture, and holds two affiliate associate professor positions at University of Washington. She conducts research in applied plant and soil sciences, publishing the results in scientific articles and university Extension fact sheets.
Linda also is the award-winning author of five books: the horticultural myth-busting The Informed Gardener (2008) and The Informed Gardener Blooms Again (2010) from the University of Washington Press and Sustainable Landscapes and Gardens: Good Science – Practical Application (2009) from GFG Publishing, Inc., and How Plants Work: The Science Behind the Amazing Things Plants Do from Timber Press (2015). Her latest effort is an update of Art Kruckeberg’s Gardening with Native Plants of the Pacific Northwest from UW Press (2019).
In 2018 Linda was featured in a video series – The Science of Gardening – produced by The Great Courses. She also is one of the Garden Professors – a group of academic colleagues who educate and entertain through their blog and Facebook pages. Linda’s contribution to gardeners was recognized in 2017 by the Association for Garden Communicators as the first recipient of their Cynthia Westcott Scientific Writing Award.
"The Garden Professors" Facebook page - www.facebook.com/TheGardenProfessors
"The Garden Professors" Facebook group - www.facebook.com/groups/GardenProfessors
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19 thoughts on “Veggie gardening science – whaddya know?”
Use of compost tea definitely needs some science behind it.
Daniel, I've written about this one frequently. The most recent version is on my web page (www.theinformedgardener.com). Just click on "horticultural myths" and scroll down to 2007, where you'll see a hot link to both the article and to the references. Short answer: there's not much useful science behind this product at all.
I agree with Daniel. I also wonder about the longevity of lawn herbicides and pesticides in composted grass clippings. Last year, when I planted tomatoes and cukes at this house for the first time, I used some nice brown grass compost from way down in the pile to which my husband had been adding for years. The tomato plants came up spindly and deformed, and fruited very sparsely, while the cukes grew ok but had the oddest shaped fruit I've ever seen. Perhaps it was the soil itself (which I lazily didn't get tested), perhaps it was the incredible strands of myceliae lacing the compost (the mound was under some pines and a couple of ash snags), perhaps it was just cussedness — but I wonder if the 'cides my husband stopped using on the lawn a couple of years earlier might have had some longevity, and if perhaps that affected the plants' growth and habits…Help — I need a scientist to shed some light, if possible! (This summer I didn't amend the soil at all; the tomatoes did fine in one bed, and some thuggish perennials (Physotegia and Boltonia) overtook the other one. My real veg. garden was across town…)
"Chest crud". That made me almost spit my coffee over my computer screen! For the scientific scrutiny screen, I nominate biodynamics. Do you know the bit where they bury the poo in a cow's horn? Well, they reckon that it only works with a cow's horn because it is, and I quote, "the perfect receptacle for cosmic energy". Oh dear.
And I hope you feel better, Linda!
Deb, there are some pretty persistent pesticides out there that, if they get into compost, can wreak havoc on unsuspecting plants. They had a real debacle in Washington State several years ago when clopyralid-contaminated compost ended up in a lot of peoples' yards. (And thanks for the warm fuzzies!)
Jimbo, the BD bizarreness has intrigued me for years! I did a column on it several a few years ago (you can find it on my web page), and since then I've been helping a couple of well-known wine writers continue to challenge the ever-growing BD movement in viticulture. (They did a nice article for The Skeptical Inquirer in December, 2007 that you can find on the SI website.)
For Perennial & Shrub planting: No Till versus Till.
Unless the soil is absolute glue and must have some ammending (I do shovel tests first) I opt for the no till method and select plants and appropriate mulch like pine bark(no shredded stuff which inhibits exchange of gases) but chipped) for the existing soil and location.
That's definitely one where the science is behind you, SJ. Wholesale soil tillage hurts soil structure and is not the best way to install permanent plantings. I'm curious about the practice in vegetable gardens – I've heard an increasing number of people say that they are firm no-tillers, letting mulch do their work for them.
And I'd like to see more research into practices that are widely subscribed to. A lot of practices seem plain silly but they have just an edge of plausibility. I suspect it's a lot like herbal remedies: some of them are anecdotes supported by confirmation bias, but some of them have been scientifically proven to work. If an idea gains enough traction that a large segment of the population is adhering to it, we ought to put up the resources to find out if it works once and for all.
What about innoculant for legumes? I've read claims ranging from not at all, to just once to revitalize soil that has been seriously abused, to all the time. You say companion planting is silly, but there have been a few things that have been scientifically demonstrated to work. In an ideal world we'd test the recommended combinations and anti-combinations and find out which, if any, we have to pay attention to. In my fantasy world, all lists of companion plants would be consistent with each other: beans would either love or hate beets, but not both. Science ought to be able to tell us if the double diggers or the no-tillers are right. Do the lunar planting folks have a scientific leg to stand on? On the one hand, it sounds like hooey, but on the other hand I can read a book outside by the light of a full moon if the night is clear enough, so maybe they aren't so crazy. And so on.
After 30 years of writing about vegetable gardening I have concluded the source of bad information is not the myths,not the biodynamic crazies; it is the County Extension Service in virtually every state. Most of the vegetable gardening information given out by Extension comes from folks who are experts on commercial agriculture. They simply dumbed down the info from acres to 1000 square feet but kept the principles of farming 500 acres in the information pack. That is why the majority if veggie gardeners still till the garden every year, use the row and path design rather than raised beds, use no mulch and weed with a hoe, use pesticides as preventive tools, and don't use succession planting. These are exactly the same practices my grandmother used in the 1940's.
Jeff, you have, unfortunately, touched on an important point. Most Extension specialists are experts on production agriculture, not urban horticulture or home gardening. I think this is part of the reason that the four of us have started this blog. The second reason is that Extension specialists (these are the ones with PhDs) are a dying breed. They aren't being replaced as they retire, as universities are putting resources towards hiring researchers who can generate huge grants to help support the university. And the main reason for this is that state legislators – and this means ultimately all of us citizens – continue to gut higher education budgets, forcing the cutback of services like Extension education. Universities still hire Extension educators, but by and large these are people who are not academic researchers and whose function is to disperse information, rather than generate it through scholarly research.
Just wanted to chime in to agree with Linda — and with you Jeff.
Linda: Too many years ago I read a wonderful article by my pal Rita Buchanan (The Weaver's Garden and many other gardening books) where she collapsed the myth of companion planting. Neither she nor I remember the name of the magazine or the year…her view is that insects are very good at handling complex enviroments and are not fooled by our feeble attempts. The fantasy of companion planting persists.
Donna, I'd love to see the article if you ever find it. I've done a pretty exhaustive search through the scientific literature already on this topic and there just nothing out there that supports these popular companion planting lists and guides.
Is anyone familiar with sustainablesites.org? Looks like some good case study work has been done.
The Sustainable Sites Initiative that you mention, Daniel, originated to create better standards for sustainability on building projects aiming for LEED certification. The US Green Building Council, which runs the LEED program, had a set of criteria for sites around buildings applying for certification, but those criteria were pretty loosey-goosey, so a number of landscape architects and horticulturists, I believe, made noise about it. The result was the Sustainable Sites Initiative, which is committed to developing much more stringent standards for sustainability in soils, hydrology, vegetation, materials selection, and human health and well-being that can be applied to LEED-candidate sites. The scale of projects varies from tiny to huge, though I don't know that anyone's been looking specifically at vegetable gardening in the Initiative.
Linda, Jeff,…I smell a potential grant proposal…
I've seen the sustainable sites information as well. I was distressed by the lack of specifics in terms of on-the-ground horticultural science, like healthy and appropriate plant selection, proper installation and aftercare, etc. I am actually editing a new book (Sustainable Landscapes and Gardens) that hopefully will get to the presses before the end of the year that discusses these practical issues for landscape horticulture. I'll certainly be posting a blog when this thing finally gets put to bed!
Holly and Linda — Jump in!! The SSI sent out a draft of its first run at dealing with sustainability issues two years ago, I think, for general comments. At that time there were huge gaping holes in it, and a lot of people wrote in with suggestions. The SSI has been working hard to make their changes, but as you say, Linda, lots of the specifics are just not there, and it would be great to get more and clearer guidance into their guidelines.