As winter continues to hold its icy grip over the middle of the country, our thoughts don’t stray too far from plants and cold. Recently one of the graduate students in our department, Nick Pershey, brought to my attention a new product called FreezePruf that claims to improve plant cold hardiness by up to 9 degrees F. Since a couple of degrees of improved cold tolerance can be a big deal (just ask a Florida citrus grower after a 29 deg. F night), nine degrees F. is huge. At first blush, FreezePruf looks ripe for the Garden Professors’ picking. The promotional claims are sensational and are followed by the obligatory exclamation points. “Just spray it on. It’s like moving your temperature zone 200 miles south!” So the obvious questions are: What is it? What does it do? Does it work?
What is it? FreezePruf is a mixture of several fairly common compounds. These include WiltPruf (a film-forming anti-transpirant), SilWet (a surfactant – helps material spread and stick to leaves), AgSil (potassium silicate), polyethylene glycol (an osmoticum – PEG is widely used in cosmetics and laxatives), and glycerol.
What does it do? To understand what FreezePruf does it’s helpful to understand how freezing injury occurs in plants and how plants tolerate freezing. First, remember that water exists in plant tissues between plant cells (extracellular) and within cells (intracellular). When plants are exposed to freezing temperatures ice forms first between cells (extracellular ice) but not within the cells. This is due to the fact that water within cells contains solutes that depress the freezing point. Freeze damage can occur in a couple ways. One is ice formation within cells (intracellular ice). Tissues can also be damaged if cells become excessively dehydrated as a result of extracellular ice formation – the ice between cells acts like a salt or osmoticum to continue to draw water of the cell and into the intercellular spaces. The formulation of FreezePruf apparently acts to depress the freezing point within the cells (due to potassium ions and PEG) and to limit cell dehydration.
Does it work? At present the only data available on FreezePruf is from the product developers in their patent application. To date, nothing on the product has been published based on peer-reviewed studies; which always makes the Garden Professors skeptical. The product development team, however, is lead by Dr. David Francko, a plant biologist and Dean of the Graduate School at the University of Alabama. Data in the patent application show improved cold hardiness on the order of about 4-5 deg. F for a variety of cold sensitive plants, mostly palms, bananas and annuals. In some cases the protection was only a couple of degrees but in one case ranged up to 9 deg. F.
What’s the bottom line? For most gardeners the principle benefit of FreezePruf would be to protect plants from the first few early frosts in the fall. The question is whether you’d rather spray a relatively untested product versus relying on tried and true methods (e.g., bringing container planters in, covering sensitive plants with old bedsheets). The developers claim FreezePruf can last up to 6 weeks – that could save a lot of dragging bedsheets around the yard.
Caveats: FreezePruf is marketed as ‘Eco-Safe’ – whatever that means – although the MSDS sheets of some of the component products indicate eye and skin irritation are possible. Until a longer-term database is available I would be cautious of unintended results. For example, could this stuff make plants more attractive to pets or wildlife? We’ve seen reduced cold hardiness in conifers using WiltPruf alone, it would be interesting to see some data on Freeze-Pruf on conifers before recommending it for use on those.
Color me skeptical. When the Garden Rant blog ran a post on this last October, I posted this comment: “I spent my doctoral research studying cold hardiness in Rhododendron. Thus, I really hoped to read the published research on this product, but was not able to find anything in the plant science databases. Perhaps Dr. Francko could provide information on where the efficacy research is published?”
No reply. And frankly, I’m not too excited about something that works on palms, bananas and annuals. (As an aside, why would anyone care about treating annuals? They’re annual!)
I might have considered buying this product if it didn’t have such a terrible name. I assume freeze-proof was already taken?
To date, there have been no published studies – just the data in the patent application they have done a variety of trials but the documentation (sample sizes, etc.)is poor. At least one article indicated a peer-review publication was in the works – but then again all the Garden Professors have 7-8 papers we could list as ‘in preparation’. There is quite a bit of interest in getting annuals through the first cold snap in this part of the country. Often times we’ll have a couple of nights of early frosts, then we’re good for two or three more weeks. So it is more common for folks to run around the yard trying to protect plants than you’d see in the Northwest.
Regarding the spelling, I think it’s a take-off on Wilt-Pruf, which is one of the ingredients.
I’ve got some borderline hardy, broadleaf evergreens I’d love to use it on if it works. If the research actually comes out, please keep us updated.
HA! Good one, Foy. I loathe cutesy misspellings.
Would publishing preclude them from patenting it later?
Absolutely not. And generally, that’s how reliable products are developed. The research is first published and scrutinized, then the product is patented and marketed. Peer scrutiny is the “quality control” that good researchers welcome before risking their credibility on a new product.
Folks, we do have a paper that is ready to go to HortTechnology, with LOTS of research that is not in the patent app. But the criticism about not having published BEFORE the product came out is valid. Frankly, we did not anticipate the Liquid Fence people getting the product out so fast. We are getting feedback from endusers who by and large have been satisfied – some have not, but I would submit that NO product will get true tropicals through 25F nights, 36 hours below freezing in a row, and 30 MPH winds.
We base the “200 mile south” claim on the approximately 1/2 USDA Zone equivalent that, on average. is added to the first damage temperature and the mortality temperature for most plants that have been tested.
MUCH of the research has actually been done on winter protection for marginal evergreens as well as frost-entension for tender plants.
We have done follow-up work this past fall on protection of mature fruits (tomatoes, strawberries,tangerines, and bananas. This will be part of a second article to HortTech.
I would invite folks to try a little bit and see what they think.
By the way, this product is certified for use sirectly on human edibles in all but 1 state (and we’re working on that one) and there are zero tox issues. It does not (so far as I can see anyway) cause plants to be more attractive to browsers.
I have limited time to check blogs, but I invite emails with questions or concerns. Thanks for listening!
I just bought FreezePruf at Ace Hardware yesterday, and applied it on roughly 1/2 of my tender plants. Forecast was 31f last night in South Brevard Co, Fl, itt only got to 36f. Let’s see what the next month does on my plants that are impacted with temps below 40, and killed below 30. More to follow in the spring, after giving this stuff a trial
Folks, I have tried the product on several of my fruiting plants to protect early spring blooms from frost. This was spring 2010. I was going to be out of town and the overnight lows were expected to be in the high 20’s. I sprayed it liberally on all new foliage. As predicted the temps were around 27-28 degrees F. Paw Paw blossoms and Hardy Kiwi were decimated. Others that are a bit more able to cope with light frosts were completely undamaged. This is by no means anything other than one persons anecdotal experience. But I did resort to sheets etc in the spring of 2011. We are experiencing an extremely early spring this season, and I am tempted to give it another go on selected plants. Will update if I am able to do so. Everything is blooming now, and tomorrow night is expected 29 degrees F.
Is there more recent information on the efficacy of this product?
Hi Devin: Thanks for the comment, See today’s post for an update.