FreezePruf revisited

I received a comment over the weekend requesting an update on an article I posted back in February of 2010 (Wow, hard to believe we’ve been at it that long!) about FreezePruf, a product that is purported to improve freeze tolerance of garden plants. The ingredients and proposed mode of action of FreezePruf are described in my earlier post, so I won’t repeat them here. Back in 2010, there were no published studies available on the efficacy of FreezePruf; just advertising claims from the manufacturer and data that were included in the patent application.

Since then, there have been two studies published on FreezePruf. One was authored Dr. David Francko at the University of Alabama, who lead the group that developed the product, and the second study was by Dr. Jeff Anderson at Oklahoma State.

Francko et al. (2011) conducted a series of trials, mainly with palms, oranges, and other warm region plants and found that FreezePruf was often highly effective in reducing freeze injury. For example, the figure below suggests that spraying plants with FreezePruf can increase freeze tolerance by 2.3 to 9.4 deg. F. (Note: the authors’ also included two additional palms and two banana cultivars in this portion of the trial; I have simplified their table to show the two extremes and an intermediate response).


Anderson (2012) applied FreezePruf based on label directions and found no change in freezing point depression in peppers, celosia, or tomatoes. Anderson also found that Freezepruf did not improve cold hardiness of Bermudagrass stolons.


So what gives? Is FreezePruf useful or not and why did the studies reach opposite conclusions? Anderson published his paper after Francko et al. but doesn’t offer a clear explanation beyond the use of different plant materials; with the exception of tomatoes, which were included in both trials but still gave different results. One possibility is that the spray may be more effective on perennial plants, especially on older leaves. For instance, in the Francko et al. study they applied FreezePruf to young and old leaves on oranges trees and found a greater and more consistent improvement in cold hardiness on the older leaves than the new leaves. For those of us in the northern U.S., this suggests the product may be of limited use. Typically our greatest concern in protecting plants from freezing is early in season; right after we’ve jumped the gun and planted our annuals and vegetable plugs. Could FreezePruf protect your new petunias from that predicted 25 deg. F night? There is no clear answer in the data so I’ll stick with the tried and true and cover my plants with old bedsheets.

Literature cited:

Anderson, J. 2012. Does FreezePruf Topical Spray Increase Plant Resistance to Freezing Stress? HortTechnology 22(4):542-546.

Francko, D.A., K.G. Wilson, Q.Q.Li, and M.A. Equiza. 2011. Topical Spray to Enhance Plant Resistance to Cold Injury and Mortality. HortTechnology 21(1):109-118.


Today I want to share something that I’ve been working on recently with Fine Gardening that is really cool!  So you know all of those lights you can buy to get your plants started over the winter?  Did you ever wonder which of those lights really work?  I’m going to leave the final answer for my article, but let me tell you, there’s a world of differences between the lights.  The best seem to be some LED lights that aren’t available yet, but are made by a company called Heliospectra.   Mostly they make high end lights for commercial producers and researchers, but they will be entering the home market soon.  Man, these lights are SWEET!

Interestingly, the other LED lights fail miserably because their light is so columnated (in other words the light doesn’t spread out), as you can kind of see in this picture (there’s another pic on facebook that shows it a bit better):

Most of you are probably using fluorescent lights, and, in terms of bang for your buck, I’d say those are pretty good.  We tested a bunch of different fluorescent, as well as incandescent lights.  Be on the lookout for the article in about a year!

Master Gardener Researchers Rule!

The Garden Professors test new products all the time.  Fertilizers, pesticides, tree wraps,compost tea, etc., they’ve all found their way into our fields and greenhouses at one time or another, but still, we can’t test everything, it’s just not possible. New stuff comes out all the time, and it’s impossible to keep up, so one of the things we love to see is people who take the initiative to test things themselves. Recently we got to see the results from a group of Master Gardeners who tested biochar on growing vegetables.   The results aren’t final yet – there’s still a few years to go – but I love the fact that this is occurring and I can’t wait to see more.

The Winter Weekend Garden Warrior

As Garden Professors, we are very careful regarding product endorsements. Actually, much energy is spent trying to bring to light weird/crappy/useless/money-wasting gardening products.

But when we feel strongly about the usefulness, quality, and utility of a product, it is our duty to pass that information along as well.

I didn’t mean to be a walking advertisement last weekend.

We were in the final throes of getting our garden cut back; Joel was laughing that I “needed another set of hands” when I came around the corner.  “Not with my fabulous Firehose Work Pants from Duluth Trading Company, I don’t!”  Thus the inspiration for this post.

All products noted are, variously: warm, waterproof, full of pockets, sharp, indestructible, dependable, and/or delicious.

Good Stuff

Boy oh boy, what a fun day!  People yelling at me from the left and from the right.  But hey, I didn’t start doing what I do to make everyone happy.  With that said….Nah, I don’t feel like attacking anyone today.  Instead, let’s look at a good renewable fertilizer: Cotton seed meal.  It’s got a reasonably good ratio of nitrogen to phosphorus and potassium — slow release of course.  Basically a waste product given a meaningful purpose.  And look at the label — no mycorrhizae or other gimmicks.  Just pure, unadulterated, cotton seed meal.  This is what I want on my garden.

Why oh Why? Christmas tree edition

Hope everyone has had a chance to digest their Thanksgiving meal and is spending a productive day at work shopping on-line.  My daughter and I enjoyed one of our Holiday traditions this weekend and brought home a Christmas tree from a local choose-and-cut farm.  This was followed by another tradition at our house known as the “Annual cursing of the Christmas lights.”  Seems like no matter how careful I am when I put away the lights when we take down the tree, they are always a mangled mess the next year.

Christmastime is also time for another ‘Why oh why?’  As in, why do people make such a big deal out of watering their tree?  Working in Extension with Christmas trees, I’m glad that we’ve gotten the word out and people are concerned with keeping their tree watered.  But is it really that hard to put water in the stand?  I use a watering can with a long stem and it seems to work fine.  Let’s look at some of the devices people have come up with water Christmas trees.  I’ve rated each on scale of 0 to 4 watering cans.


The tree IV.  I’ve mentioned this one on the blog before.  The theory here is that the tree will suck up water from a reservoir you attach to the trunk.  Trunk injection is possible with conifers but requires pressure and resin quickly fills the hole. 0 cans.

The watering cane.  OK, maybe you’ve got back problems and bending over with a regular watering can could be an issue. 4 cans.



Water funnel system.  I’m not sure the video convinced me this is faster and easier than the watering can. 2 cans.

Water reservoir cleverly disguised as a package.  Assuming the issue is you don’t like to bend over and put water in the stand, I don’t see where bending over to put water in a fake package is a big improvement.  And what happens if you forget which package is which? 2 cans.

Funnel cleverly disguised as an ornament.  Gets around the bending over issue, but can you really hide the tubing? 3 cans.



Christmas Vacation anti-transpirant.  According to the advertisement you can put this stuff in the first time you water the tree and then you are good to go for the next month.  The same product is sold as ‘Stasis’ and is used to protect bedding plants from wilting during shipping.  The theory is that the product induces stomatal closure by increasing abscisic acid levels.  I’m withholding judgment on this one until I see some data one way or the other, but to say I’m dubious is an understatement.


Keeping a Christmas tree hydrated is like most things; you can’t go wrong with the tried and true.  A fresh tree that is kept well-watered will retain needles for weeks and is very unlikely to be involved in a tree fire.   A tree this is allowed to dry, on other hand, is another story.  So before depending on a gimmick to keep your tree watered ask yourself if you’re willing to bet your house on it.


Deconstructing the cornmeal myth

Back in June of 2010, I wrote about an online column that recommended applying cornmeal as an antifungal soil amendment. (Important note: we are not talking about corn gluten meal. Just cornmeal.) The upshot of the post was while some gardening personalities extol the use of cornmeal to kill soil pathogens like Rhizoctonia and Sclerotinia, no published science supports the practice.  The post was effective in encouraging the author of the referenced online column to update her information, but the controversy didn’t die. In fact, new comments have been added to the original post on a fairly consistent basis, mostly in the form of personal anecdotes or angry rebuttals. Some commenters, however, have tried to carry on rational discussions, so today we’re going to look at cornmeal from a slightly different angle: what effect does it have on microbes in general?

To start, let’s look at the Stephensville, Texas research that’s most often highlighted by cornmeal proponents.  There’s no peer-reviewed work published on this specific research, but in an online copy of the Texas Peanut Production Guide I found a paragraph referring to “Biological Control of Soil-Borne Fungi.” Here it is in its entirety:

“Certain fungal species in the genus Trichoderma feed on mycelium and sclerotia of Sclerotinia minor, Sclerotium rolfsii and Rhizoctonia spp. All peanut fields in Texas tested to date have natural populations of Trichoderma. For several years, tests have been conducted in Texas using corn meal to stimulate Trichoderma development as a way to control the major soil-borne disease fungi. When yellow corn meal is applied to fields in the presence of moist surface soil, Trichoderma builds up very rapidly over 5 to 10 days. The resulting high Trichoderma population can destroy vast amounts of Sclerotinia, Sclerotium and Rhizoctonia. This enhanced, natural biological control process is almost identical to the processes that occur when crop rotation is practiced. The level of control with corn meal is influenced by organic matter source, soil moisture, temperature and pesticides used. Seasonal applications of certain fungicides may inhibit Trichoderma. Testing will continue to determine the rates and application methods that will give consistent, economical control.”

And that’s all there is on the topic. Most scientists would conclude that further testing was inconsistent and the researchers abandoned their efforts without publishing anything further. But this summary is at least a starting point, though it contains no data, references, or even authors.

First, there’s no argument that Trichoderma is a powerful antagonist of some nasty pathogenic fungi. Likewise, cornmeal most certainly can encourage the growth of Trichoderma, both in the lab and the field.  But cornmeal also encourages the growth of many other fungi – in fact cornmeal agar is commonly used for culturing fungi in the lab. So what about those three pathogenic fungi mentioned in the Texas peanut guide? Do they like cornmeal?

Indeed they do! Published research (about 20 or so articles) shows that cornmeal (not cornmeal agar) has been used to enhance growth of Rhizoctonia fragariae, R. repens and R. solani, Sclerotinia sclerotiorum and S. homoeocarpa, and Sclerotium rolfsii. In some cases the pathogens became more virulent in the presence of cornmeal.

Cornmeal is nothing more than a carbohydrate-rich resource that can be used by many microbes. If you happen to have a lot of beneficial fungi in your soil, cornmeal will feed them. If you happen to have pathogenic species in your soil, cornmeal will feed them too. So it depends on what fungi are already living in your lawn, vegetable garden, or rose bed on whether cornmeal will help, or just make disease problems worse.

The best thing to do – as the paragraph from the peanut guide suggests – is to mix things up a little in your landscape. Use mixtures of lawn grasses rather than growing a monocultural turf. Rotate plant placement in your vegetable garden every year. Add a microbe-rich organic mulch to your rose beds. Natural methods will keep pathogens in check much more effectively than a hyped-up home remedy that’s anything but antifungal.

UPDATE: Since this is a myth that refuses to die, I’ve published a peer-reviewed fact sheet on the topic. Feel free to pass on to others.

Poisoned bird seed and trust

Over the years I’ve said some nice things about Scotts Miracle-gro products, such as one of their potting soils, and some not so nice things, such as with their Round-up resistant Kentucky bluegrass. I’ve never thought of them as a particularly good or particularly bad company, just a company trying to do the best it could while being reasonably honest about what it was doing (You could argue that they tried to pull something fancy with the Round-up resistant Kentucky bluegrass, but I’m going to give them the benefit of the doubt and say they were just exploiting an obvious governments loophole – not exactly good, but hey, it’s a dog eat dog world out there).

But then the news broke that they had applied insecticides illegally to their wild bird food products, falsified pesticide regulation documents, distributed pesticides with misleading and unapproved labels and distributed unregistered pesticides.  If you haven’t seen the article yet you need to look here.


Anyone who has read much of what I write knows that I try to tell the truth about products to the best of my ability, to do this I rely on a lot of different sources of information, including information provided by the company itself.  I trust that, for the most part, companies try to do what they say they’re doing (or not doing) in terms of letting us know what’s in their products.  At the least I assume that they follow the government’s rules and regulations.

This is a serious breach of my trust.

How am I supposed to deliver the facts about Scotts Miracle-Gro products when I can’t trust them to do what they say they’re doing?

I mean really?  How can I talk about their products again?  I have no idea what’s in there.

I’m trying to think of something pithy to say next – but I’ve got nothing.  I’m deeply disturbed that this could happen, and, at least for the time being, I just can’t, in good conscience, trust this company or its products.   Sure, the company is saying all the right things now, but that’s not enough.

Here’s a thought – maybe they could publicly state that they’re not going to release the Round-up resistant Kentucky bluegrass – you know – to prove that they really are serious about avoiding doing things that might disturb the environment.  And then actually do it.  Yes – that would be a good start.

The Wrong Message

Every once in awhile I’ll see a new garden product that really speaks to me.  Something that promises spectacular results on some garden problem that I’ve had to deal with before and attacks it in a novel way.  Then I’ll read the advertising materials for the product and be let down before even trying it.  Such is the case for a new product called Liquid Ladybug (which, by the way, is one of the niftiest product names that I’ve ever seen — so there’s a win for the company!).

According to the manufacturer Liquid Ladybug is a spray-on product which kills spidermites, evaporates quickly from the plant, and which has organic plant oils as its main active ingredient.

So far so good — and even believable.  Plant oils can kill spider mites.  Of course simply wiping the plant with a cotton swab soaked in isopropyl alcohol can do that too — or you could easily make up a soapy spray to spray on the plant which can do the same thing.  Still, the claims don’t seem too bad so far.

Here’s the part that I have a problem with — you can, and are all but encouraged to, spray this stuff with no protection (like gloves).  See the website here .  Is this a bright thing to advertise?  Many plant oils don’t agree with eyes, mucous membranes, or beneficial insects, and let’s not even get started with allergies!  In my opinion this is reckless, foolish advertising.  Pesticides, organic or not, need to be respected.  Without that respect we inadvertantly put ourselves into bad situations. Another problem with this products is that it is likely to kill any predatory mites or other soft bodied beneficial insects just as readily as it kills bad mites.

And check out the price of this stuff!

My advice, skip this product and use insecticidal soap, or, if you’re anxious to try something new, try a beneficial insect such as the big eyed bug or minute pirate bug.

Sugar and Spice and Misnomers

At a lively hobnob with friends and colleagues, the discussion ranged from critique of the Virginia Tech offensive line to the logic/mystery behind commercial carbon offsets.  Someone mentioned Domino Sugar’s efforts in that direction. Apparently their product has been certified “carbon free” by a business carbon offsets program that they pay a fee to. This led to hoots and snorts as to their selection of terminology since it involves a molecule (sucrose) that is 27% carbon.

From the fascinating thus time-eating Serously, don’t click the image unless you’ve got an hour to burn.

I’d forgotten all about it until I saw a post (on of all places) that also brought it up.  The product in question:

Now I can appreciate that the point of this branding/certification is not to advertise a dearth of carbon; rather their good intentions,  as it is Carbonfree, not carbon free.  But the marketing staff perhaps need to be reminded that in addition to the inorganic carbon gases that are of major concern, carbon is a part of all organic life…and essential to both sweet tea and the suffering of Biochem students everywhere.