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science behind frost protection?
johngreen
Posts: 58
I live in Canada and usually can't plant until mid may. I'm trying to get a better understanding of the science behind frost and how a simple plastic bottle can protect your plant from frost.
how much does it actually heat your plant up? and how does it work? Could I get away with planting in early may when there is a chance that night temps might dip down to -3C?
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Assuming the snow has gone, you can warm up your beds by covering them with black plastic sheets for a week or two. This will absorb sunlight and warm up your soil so you can plant a bit earlier. Individual plastic bottles will offer less protection to seeds and small plants than a bigger cloche that can protect several plants at once.
Here we can buy rigid plastic cloches that can be sealed at the ends or fitted together to make a long cloche. See the third image here - https://www.google.be/search?q=rigid+plastic+cloches&biw=1588&bih=747&site=webhp&tbm=isch&tbo=u&source=univ&sa=X&ei=FuMPVd_rNcXEPe-mgOgK&sqi=2&ved=0CCsQsAQ$ and there are many more forms available. You could also make one by simply curving over a sheet of corrugated plastic and staking and pinning it in place and sealing the ends.
They should give 3 or 4 more degrees of frost protection than a single bottle and allow you to get ahead with your sowing and growing and eventual harvesting.
John, damage occurs when frost actually settles on the plant. This causes the internal structure of the plant to freeze leading to death/damage. Covering the plant stops this, generally the thicker the covering, the more protection a thing gets. Layering affords even more protection, just like clothing, trapping layers of air between each layer. I use fleece down to temperatures of -5, and only removing it when the temperature rises. A cloche or bottle will help, but fleece would afford more protection. Obelixx advice is perfect for the temperature you describe, personally I prefer fleece, but either would be sufficient.
Hi thanks for reply, was looking to understand how exactly frost works though. How is it that the bottles and cloth protects the plants? does it keep heat in? and for how long? how is it that a bottle can heat a plant enough at night, when there is no sun, to protect it from frost? or is it a combination of a slight temperature increase and the protection from the open air? etc
Ah okay thanks, that's what I wanted to know. Thanks to both of you for your help! Friggen snow here this morning..I guess it's only march though but I still hate the sight of it!
The protection acts like a coat you'd put on to go outside. You need different layers of protection and insulation for different degrees of frost and so do plants. Whatever you use you need to make sure it doesn't touch the plants as they'll get frosted that way too.
Fleece is fine in Britain which rarely gets below about -6C in most places. My garden in Belgium gets to -15C in normal winters but without an insulating blanket of snow. The last two winters have been very mild here but previous ones have seen temps go well below -20C and I have lost many usually hardy shrubs and trees and perennials because I can't fleece or cloche my entire 1 acre+ garden. I keep the cloches for early veggies and hardening off new sowings of perennials.
belgium, i bet its beautiful there! I have a lot of plastic that I can get for free so I will have to use that. I was thinking about building long tents for my garden
Could you build cold frames you place directly over the garden soil.. then remove once things warm up properly? Open them on warm sunny days, close again on cold nights. You can even put a lit candle inside during those really freezing cold nights to keep it above freezing (you'd need to experiment to see how many candles for the size/temp ratio). Once all chance of frost is gone, you can take them apart and store until next year.
yeah thats what i think i will do, minus the candles though, or maybe i will just start a lot of stuff indoors,
Such a simple, neat idea. I shall definitely keep it in mind for my greenhouse if we get a real winter next year.
wow i should use those in my house next winter! my heating bill is pretty high usually