The Garden Professors™

Friday puzzler: Opening a can of worms

Part of being a Garden Professor is evaluating, interpreting, and passing on good science to the rest of the gardening world. I was recently made aware of two articles soon to be published in Crop Protection and Pedobiologia, both peer-reviewed, scientific journals. (You can download these articles just by clicking on the highlighted journal names.)

Briefly, what one expects from a scientific article is (1) a statement of the research question (the hypothesis) to be investigated, (2) a clear description of the materials used and procedures followed, (3) a listing of the results, along with their statistical significance, and (4) a discussion of the results, including whether they supported the hypothesis.

Both articles focus on the use of vermicompost teas as a way of reducing pest damage on greenhouse grown crops. If you’re not familiar with this product, it’s made using worm castings and water in an aerated system. The researchers conducted one large experiment and divided the results into two parts for publication. Therefore, the materials and procedures were the same for both articles, and you’ll also see that the conclusions are likewise the same. (My point – you really only need to read one of these articles.)

I sent these articles and my evaluations to my GP colleagues; at least two of us will be sending letters to the editors of both journals expressing our concerns. Jeff thought these articles provided a great opportunity for our blog readers to look over our shoulders and see what we do. We don’t question the results that the investigators got, nor do we have any argument with the statistical analysis. We do question the authors’ interpretation of the results.

So here is your assignment for the weekend:

(1) Read the methods section carefully to understand the differences between the treatments (the vermicompost tea addition) and the control. Can you think of an alternative reason for the results the researchers found?
2) What additional flaw do you see in the discussion section in terms of the proposed mechanism of protection conferred by the vermicompost tea treatment?

On Monday, I’ll post the draft of the letter that we’ve drafted to the journals.

Oh, and if you have any questions, please post them! We will answer them the best we can.

Soap and Deer

Short post today — Linda appears to have transmitted her illness electronically over a couple of thousand miles — Thanks Linda!

I was reminded yesterday that it’s almost time for gardeners to start worrying about winter deer damage. With that in mind I thought I’d share with you my favorite research article on the subject. It’s a little paper by Michael Fargione and Michael Richmond and published about 18 years ago. You can find it here.

This paper attempts to establish how repellent bars of soap are to deer and comes up with some very interesting conclusions. The first thing you should know is that no one type of soap appears to be better than another. The second thing you should know is that soap does appear to stop deer from feeding around the soap — but the best you can hope for is a radius of protection of about a meter from the bar of soap itself — Can you imagine what that would look like if you were trying to protect the lower limbs of a large tree? And finally, bar soap appears to attract voles. Based on my reading, and my limited experience, I’ve found that almost everything that people say repels deer does repel deer — human hair, peeing around a tree, predator urine, dried blood — the issue is how long these repellents stay effective and how effective they are when the deer get really hungry. The most effective commercial deer repellents tend to have “putrescent egg solids” in then (rotten eggs) — I once had a graduate student who needed to protect some hazelnuts from deer and she found that a mixture of a few eggs (2-4) mixed in a quart of water and sprayed onto the trees worked pretty well — and no, the eggs weren’t rotten. This mixture should be sprayed about once every two weeks if possible.

Inspecting nursery plants, part ll

Well, I’m recovering from this simply horrific chest cold or whatever it is and feeling brain function returning. The last time we were at our virtual nursery, we were looking for root flare and inspecting the trunk for damage from improper bagging. Since we’re already down on our hands and knees, let’s consider roots. In general, you really don’t want to SEE roots, except where they meet the trunk (the root flare). The presence of coyly crossed “knees” in this photo is a clear indicator of a plant that wasn’t potted up quickly enough:

Likewise, while the fused, circling woody root mass in this next photo might be aesthetically interesting, it sure doesn’t make a functional root system:

It’s pretty easy to avoid these types of plants, because you can see the root problems before purchasing. The hidden root problems, such as those I’ve shown in earlier posts, are tough to find until (or if) you take all the extraneous stuff off of the root ball.

Finally, there is a new production practice that really fries my potatoes. What really makes me angry is that these trees had absolutely LOVELY roots – a nice flare, woody roots spreading radially – and then they were butchered – and left unprotected:

I can think of no legitimate reason for this practice. I’ll be curious to hear my colleagues’ thoughts, as well as those from the blogosphere.

Compost Tea? How About Compost Pee!

My news tab in Firefox is the BBC “latest headlines” page. It’s a great place to get pretty darn unbiased news plus the U.K. equivalent of “News of the Weird”. SO, relative to our ongoing discussion of composting…here’s a story ripped directly from the BBC headlines. Follow the link for a video (interview, that is).

Disclaimerage: I nor any of the other Garden Professors endorse this activity, nor any claims as to its usefulness, scientific relevancy, harrumph harrumph, etc,. etc,. etc. We do, however, fully endorse garden-related humor!

********

Pee To Help Make Your Garden Grow

Gardeners at a National Trust property in Cambridgeshire are urging people to relieve themselves outdoors to help gardens grow greener.

A three-metre long “pee bale” has been installed at Wimpole Hall.

Head gardener Philip Whaites is urging his male colleagues to pee on the straw bale to activate the composting process on the estate’s compost heap.

He said the “pee bale” is only in use out of visitor hours, since “we don’t want to scare the public”.

He said: “For eight weeks now, male members of our garden and estate teams have been using the outdoor straw bale when nature calls. The pee bale is excellent matter to add to our compost heap to stimulate the composting process; and with over 400 acres of gardens and parkland to utilise compost, we need all the help we can get.

“There are obvious logistical benefits to limiting it to male members of the team, but also male pee is preferable to women’s, as the male stuff is apparently less acidic.”

By the end of the year, it was calculated that the 10 men from the 70-strong garden and estates team will make more 1,000 individual trips to the pee bale, contributing towards the compost for the estate. The estate said it will have saved up to 30% of its daily water use by not having to flush the loo so many times.

Rosemary Hooper, Wimpole estate’s in-house master composter, said: “Most people can compost in some way in their own gardens. Peeing on a compost heap activates the composting process, helps to produce a ready supply of lovely organic matter to add back to the garden.

“Adding a little pee just helps get it all going; it’s totally safe and a bit of fun too.”

Story from BBC NEWS:
http://news.bbc.co.uk/go/pr/fr/-/2/hi/uk_news/england/cambridgeshire/8357134.stm

Published: 2009/11/13 00:40:21 GMT
© BBC MMIX

Will cocoa mulch kill my dog?

Recently I was asked to comment about a rash of e-mails floating around cyber-space concerning the toxicity to dogs of mulch made from crushed cocoa bean hulls. Cocoa mulch is by-product of cocoa production. The dark brown mulch is aesthetically and aromatically pleasing, giving the garden a rich, chocolately scent. Since theobromine, a naturally occurring compound in chocolate is toxic to dogs, the internet is now filled with cyber-legends of dogs eating cocoa mulch and keeling over dead.

According to an article published in the Journal of the American Veterinary Medical Association (JAVM June 1, 2006 p. 1644), cocoa bean husks can contain up to 2.98% theobromine. The JAVN article state “no reports of lethal toxicosis from ingesting this mulch have been filed with the ASPCA Poison Control Center this year (2006). In 2004 and 2005, 16 reports of single exposure to the mulch were received, none resulting in death.”

The ASPCA posts this comment regarding cocoa mulch on its website:
“Dogs consuming enough cocoa bean shell mulch could potentially develop signs similar to that of chocolate poisoning, including vomiting and diarrhea. In cases where very large amounts of mulch have been consumed, muscle tremors and other more serious neurological signs could occur. To date, the ASPCA Animal Poison Control Center has not received any cases involving animal deaths due to cocoa mulch ingestion. One key point to remember is that some dogs, particularly those with indiscriminate eating habits, can be attracted to any organic matter. Therefore, if you have a dog with such eating habits, it is important you do not leave him unsupervised or allow him into areas where such materials are being used.”

It should be noted that processed cocoa mulch may contain much lower concentrations and some manufacturers market cocoa mulch that is ‘Pet safe’. Consumers should look for products that are tested and certified theobromine free.

As always, I stand by my recommendation to use locally processed wood products such as ground hardwood bark and ground pine bark. Plants grow well in these mulches, which are typically among the most cost-effective and natural looking (to me, at least) mulches available, and they are renewable and help support your local economy.

If Harvard Says That It Works Then It Works Dammit!

So back in September my department head (who is, for all intents and purposes, my boss) handed me a New York Times article (http://www.nytimes.com/2009/09/24/garden/24garden.html) about the grass at Harvard which is now being managed organically. We share the opinion that many organic techniques, such as compost tea, are “Voodoo Science” (that’s a term I stole from Mike Dirr) and so she thought I’d be interested in the techniques that Harvard was using. She didn’t say it explicitly, but I think she thought I’d get a laugh out of it. And I did….Along with a funny feeling in my stomach.

After looking at the article I just couldn’t resist going to Harvard’s website (http://www.uos.harvard.edu/fmo/landscape/organiclandscaping/) and finding out all of the stuff that they’re doing to make their grass look wonderful. And, to be honest, much of it is great. They’re aerating more, they’re adding compost to the soil, they’re using fewer pesticides. All of which I wholeheartedly agree with.

And then they’ve got this whole compost tea thing going on. In fact, they actually include information on how to make a compost tea brewer and different recipes for these compost teas.

For the uninitiated, compost tea is a mix of water along with other things — such as a carbohydrate source (like molasses, or flour, or sugar, etc) and maybe even a little bit of organic fertilizer — into which a “teabag” (usually something like a burlap sack) is dipped which contains compost. Air is usually bubbled through the mixture, in part to reduce the likelihood of bad bacteria, like E. coli, infesting the mix (research has shown that this doesn’t work). Supposedly the good microbes from the compost start growing in the spiked water producing a “tea” which is packed with microbial goodness for your plants. The microbes are supposed to revitalize the soil as well as, potentially, helping it to ward off plant diseases.

Bullpucky.

This isn’t to say that I don’t think soil microbes are important because I do — they’re vitally important! But why is it that some people think compost tea is needed to add them? As a researcher and professor I’m supposed to try to stick to saying what the research supports. Following those rules I’d like to add to a comment that Linda made the other day. The research currently shows that compost tea is unlikely to do a darn thing for you — at least in terms of the microbes which it adds. Compost teas, like the ones from the recipes at Harvard, will often have nutrients in them from the added compost (nutrients will leach into the water from the compost), or from fertilizers. These nutrients can obviously provide some fertility to the soil (or to the foliage). Beyond that fertility I am completely unconvinced of the value of compost tea.

So why are the people at Harvard raving? Well, it looks to me like they did a bunch of good things, incorporated one Voodoo science technique, and then attributed an inappropriate amount of their success to the Voodoo science technique. Go Harvard!

I’m going to close with an image of some roses (these are a small sample from a larger experiment) that I treated with compost tea to protect them from disease. Don’t they look nice? I have a number of researcher friends who have also tried these teas. None has had a positive experience.

To Prune Or Not To Prune, That Is The Question…

Dabney rules!

“Dabney! No! Wait!” Just kidding. Dabney Blanton, our lovely and talented horticulturist, knows not to prune the Artemisia in the autumn.

I imagine most gardeners have experienced a frost or freeze by now [exceptions: our Southern Hemisphere readers (howdy to Jimbo)…or anyone in the deeeeep south].

The perennials here in Blacksburg have taken a couple of hits; time to start trimming things back. In the Hahn Horticulture Garden and in my own personal garden, we like to leave perennials and ornamental grasses up as long as possible – gives us something to look at besides mulch, plus the wee birdies enjoy it.

But some perennials just look yucky after a freeze.

Case in point: foliage of the popular perennial Artemisia ‘Powis Castle’ resembles graying Kleenexes, hanging on the tips of the branches. HOWEVER, do not cut this back in the fall. It, like many other shrubby perennials, is sensitive to early winter whacking, in my experience, Buddleia and Caryopteris also fall into this category. Apparently the severe pruning sends a message to the plant to break bud – new shoots can appear and then “zap!” Wait until new buds appear in the spring, and be careful not to cut back too hard. I’ve killed a few that way, thinking I was doing them a favor.

“Cut ‘em back, cut ‘em back, waaaaay back!”

The best resource ever on maintaining perennials is Tracy DiSabato-Aust’s The Well-tended Perennial Garden. I should get kickbacks, as much as I’ve promoted this book! Truly a wealth of info – when should you cut it back, will it rebloom if deadheaded, don’t do [whatever] or you’ll kill it – all broken out by genus. Outstanding!

Veggie gardening science – whaddya know?

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.)

The World According to Chub

Following up on Holly’s theme of “I can’t believe I get paid to do this”, last Wednesday I participated in a walk-through and inspection of the Justin ‘Chub’ Harper Collection of Dwarf and Rare conifers at MSU’s Hidden Lake Gardens in south central Michigan. The Harper collection is widely regarded as one of the premier collections of rare and unusual conifers in the world.

Harper Conifer Collection with fall color background. Photo: Jack Wikle.

A little background: Chub Harper was the former grounds supervisor for John Deere’s world headquarters in Moline, IL, an avid plant collector, and a founding member of the American Conifer Society (ACS). He acquired hundreds of rare and unusual conifer specimens around his home and eventually had to lease a nearby lot for the overflow – demonstrating that ACS also stands for ‘Addicted Conifer Syndrome’. In the early 1980’s Chub donated 300 conifers to Hidden Lake Gardens to establish the Harper collection. All of the plants were balled and burlapped by hand and shipped in three semis to Michigan. Chub continued to add plants to the collection and today the collection includes over 500 accessions.

Chamaecyparis pisifera ‘Filifera aurea’

I met Chub about 8 years ago and with his guidance and inspiration started a series of ‘Conifer Corner’ articles in the Michigan Nursery and Landscape Michigan Landscape magazine. (visit my faculty page for .pdf’s of some sample articles http://www.hrt.msu.edu/bert-cregg/pg5). Once or twice a year Chub would travel from Moline to Michigan to inspect the collection along with members of his conifer posse. To me, the most impressive thing about the walk-throughs was how absolutely ruthless Chub was in disposing of under-performing plants or plants with continual pest problems. “Time for that thing to take a ride on the chipper truck” was a favorite Chub-ism. Hidden Lake Gardens has a garden staff that could spray pesticides or prune away dead material regularly; but Chub wanted none of it. This is not to say that Chub was into organic gardening; as far as I know he had no particular aversion to chemicals. Rather, he felt the mission of the collection was education and that maintaining plants in an artificially superior condition would mislead the public into thinking some conifers were better suited than they actually were.

The Conifer posse at the 2007 walk-through. Chub Harper is 3rd from left, back row.

Chub passed away unexpectedly earlier this year and last Wednesday’s walk-through was the first evaluation of the collection without him. The conifer posse carried on, led by former ACS President Dennis Groh; Chub’s longtime friend Jack Wikle; and Sam Lovall, the landscape architect who developed the original design for the collection. We found homes in the collection for several new specimens including an Abies concolor ‘Charmin’ Chub’ and condemned a few underachievers to a ride on the chipper truck. Chub left many legacies; the most obvious and tangible is the Harper Collection and the staggering generosity it represents. Imagine dedicating half your life to acquiring and cultivating a world-class collection and then simply giving it away. Just as important, however, is the legacy he left with those who knew him, who felt his passion for conifers, and were inspired by him.

Pinus parviflora ‘Cleary’

I see the light!

Here’s the follow up picture from Friday’s puzzler:

As you can see, there’s a street light near the lower half of the maple. (I cleverly hid it behind the utility pole in the first photo.) The green part of the tree never received the message that days were getting shorter, since the street light is bright enough to interrupt the dark period necessary to initiate dormancy.

This is one of my favorite phenomena unique to urban environments. It doesn’t appear to hurt the tree, although the green leaves will die before the tree can scavenge their nutrients. If more of the tree were affected, I’d be more concerned.

Congratulations to Planting Oaks, who nailed this right off. And kudos to those thoughtful alternative explanations, all of which could logically have had an impact on color change.