Techniques for combating frosts

As the snow starts to melt, I'm starting to think about what big projects I'd like to take on this year. Part of what I'm looking to do with my land over the next few decades is experiment with methods to grow things I "shouldn't" be able to. My biggest challenge isn't so much our winters (which receive a lot of snow, but are relatively mild in temperature) but rather our early & late frosts.  What I'd love to start doing is compiling a list of techniques for combating frosts, particularly for fruit (apple/pear) trees and berries. Unfortunately while I've read a lot of anecdotal "this south facing rock face provides a perfect micro-climate for squash" types of information, I find myself hungry for a more comprehensive list of strategies for mitigating frost damage. I realized what I wanted was a big list to choose from so I could choose which ones I want to experiment with.

Here's some examples of what I'm thinking:

Berm / Hugel Sunscoops

Berm / Hugels to channel frost pockets away from growing areas

Ponds on northern side of crops

Planting trees in between tall hugel beds

Large boulders and rock walls to absorb/release heat

Planting trees on North facing hills (to slow morning thawing)

Fruit Walls

Underground greenhouses

What else should I be looking into? What books or articles would you recommend to learn more? I feel like I learned a lifetime of information from Sepp Holzer's Permaculture and Mike Oehler's Underground Greenhouses, but I'm also certain I've got a lot more to learn.

Kyle Neath wrote:What else should I be looking into?

I highly recommend exploring genetics... Plant varieties/species that can survive the cold/frosts. Plant genetically diverse crops and replant the offspring of anything that survives the cold/frosts.

I'm not sure if I read it correctly or if I'm going to give you anything you were looking for but here I go.

We can have 60-70defree days for weeks and then get hard frosts. My biggest problem is keeping plants from coming out of dormancy too soon. The perfect tree will be dormant until mid to late May. This is hard where we don't get a ton of snow and have freakishly fluctuating temperatures. So Kraters are my answer. They keep pockets of cool air around the trees and prevent them from doing anything foolish before it's time.

I highly recommend exploring genetics

Yes, good point! I'd love more points to learn about exploring genetics w/ fruit trees & bushes in particular since it's a much different game than annuals. The best information I've found so far is this PDF from University of Idaho. I struggle to find good local advice on this topic as most advice is "move to the central valley where you can grow anything."

Elle: I think kraters definitely fall into this category. I have a dream one day to build a massive crater… but I suspect that's quite a few years down the road.  One area I am really interested in learning more about is the balance & tradeoffs of avoiding frost pockets (high ground, south facing slopes) and encouraging them (kraters / north facing slopes). I've heard both sets of advice for "cool climates" and I can understand the rationality between both of them. Avoiding frost pockets increases the overall temperature, perhaps avoiding frosts. On the other hand, frosts themselves aren't always destructive — it is the rapid freezing/thawing that is damaging, so encouraging a slow thaw might avoid the damage of a frost. Where I fall short is understanding which one is appropriate in what kinds of situations.

Hi

try planting vulnerable plants under trees. I get less frost formation in fall and in spring the soil warms up more slowly in the shade. Also there are plants like red mulberry that bloom and fruit throught the spring and summer so if a frost kills off blossoms you can still get a yeild. creating losts of frost barriers creates both cold and warm places. if you want something to bloom later you can put it in a frost pocket and anything that can survive a late spring frost in the sun trap. If a plant is sensitive to frost and sets all of its flowers out at once try putting up a frame around it so you can cover it easily.
good luck  

That's what fall leaves are for.  I started some potatoes in January, and while we have had some nice potato weather in Georgia this winter, an occasional hard frost can set them back to square one.  So I'm learning to watch the weather forecast, and when a hard freeze is predicted (usually for only 2 or 3 nights), I start raking up leaves and dumping them on the spud plants.  Then when the growing weather returns, I go and clean out the leaves so that the potatoes can get some sun.  

I also have some row covers, and they protect down to the mid-20s as long as there is no wind to blow under them.  Combining craters with these two covering tricks may buy you a much longer growing season.  

Kyle Neath wrote:I'd love more points to learn about exploring genetics w/ fruit trees & bushes in particular since it's a much different game than annuals.

My strategy is to plant hundreds of seeds, and after the first winter cull anything that shows the slightest bit of frost damage. Then cull after the second winter, and after the third... Then when they flower, select for later flowering plants that are more likely to avoid frost damage to the fruits.  

Because the generation time for trees can be so long, it helps to obtain seeds from local trees, because they have already proven themselves in the area. I'm currently on my third generation of selection for walnut trees for my climate. A fourth generation is expected any year now. I didn't do the first two generations of selection, but my people did.

Around here, old farmers use 10 or 20l buckets and spread them around the fields to prevent frost.

Kyle Neath wrote:

Elle: I think kraters definitely fall into this category. I have a dream one day to build a massive crater… but I suspect that's quite a few years down the road.  One area I am really interested in learning more about is the balance & tradeoffs of avoiding frost pockets (high ground, south facing slopes) and encouraging them (kraters / north facing slopes). I've heard both sets of advice for "cool climates" and I can understand the rationality between both of them. Avoiding frost pockets increases the overall temperature, perhaps avoiding frosts. On the other hand, frosts themselves aren't always destructive — it is the rapid freezing/thawing that is damaging, so encouraging a slow thaw might avoid the damage of a frost. Where I fall short is understanding which one is appropriate in what kinds of situations.

My kraters are 3 feet deep, around 20 feet round. Small kraters can do big things!

Kyle Neath wrote:Avoiding frost pockets increases the overall temperature, perhaps avoiding frosts. On the other hand, frosts themselves aren't always destructive — it is the rapid freezing/thawing that is damaging, so encouraging a slow thaw might avoid the damage of a frost. Where I fall short is understanding which one is appropriate in what kinds of situations.

I don't know much but I've been thinking about this a little myself.  My thinking is that if the frost issue is related to freezing a blossom on a frost hardy fruit tree (peach), the krater or northfacing location that delays flowering may be the better approach.  When you're worried about frost killing the entire plant (basil), the sun scoop, southern slope frost avoidance methods may be better.  

Another approach I'm interested in is snow control.  Using a snow fence or windblock to deliberately put snow around the tree that you want to have delayed flowering on.  Along with that having a shade device or nearby tree that shades that snow and the ground until April to help keep it cool.

I'll have to do more research but I'm interested in trying a krater type recess on a south facing slope with shade and snow catching to protect a small shrub that is nowhere near hardy in my area.  If I can get enough snow covering it in the winter, it may not get much below freezing over winter.  Then by the time the snow melts it should be past the frost time for flowers.  Since it would then be south facing the hole/krater may act as a sun scoop to warm it up and make it happy until fall.  It may even give it extra frost protection in the fall if there's a frost avoidance berm on the uphill side.

I have no idea if this will work but if anyone has thoughts on it, please chime in.

For us in Maine, our way of capturing heat is to capture snow. If snow cover is 6 inches deep, the coldest the ground gets is 31 degrees. Compared to the 18 below zero (f) we had yesterday, that is very warm, but promotes dormancy, which is what we want. Two weeks ago it was a crazy 57 degrees here and as I stated, really cold yesterday, that killed a lot of stuff I am afraid, but keeping it dormant...that would save it.

Here on this hill, I have found swales work best at catching the snow. I have probably a mile of them installed, and even after weeks of high winds, sun and warm temperatures, the swales are several feet deep with snow. In fact they are level full.

Another way we promote snow accumulation is boughs. We have a lot of spruce, fir, pine and hemlock boughs here and covering plants and vegetables really protects them. We even "bank" our houses with them to keep the wind from blowing through the old stone foundations. Here roses are tough to raise because of the cold, but boughs covering the plants always kept them just warm and snuggly enough to thrive the next year.

I like the idea of craters, but think a big one would defeat the purpose. You want the wind and air to pass overhead, the interior filling with snow. Too big of a crater would defeat that.

Assuming you have a lot of elevation difference, you can use that too. My father lives 517 feet from my house, yet is 60 vertical feet down from me. I can plant my garden about 2 weeks sooner than him because there is a micro-climate frost line halfway from his house to mine.

I would also think drainage plays into this. I have gravelly loam type soil here so the water permeates through it easily. Not sure what role that plays on frost and dormancy, but it may be something to research.

Travis Johnson wrote:I like the idea of craters, but think a big one would defeat the purpose. You want the wind and air to pass overhead, the interior filling with snow. Too big of a crater would defeat that.

Thanks for the info Travis!  How big do you think is too big for a krater to hold snow?  I'm imagining a 5' diameter hole that is 2-3 feet deep...

And when you say your swales hold snow, is that affected by the direction of prevailing winds or solar orientation?  Or are all your swales oriented the same direction?

I think you will be okay with craters that size. Now this is all on me and not you at all, but when I read about big craters, I was thinking a lot bigger. Now as I said, that was my fault as my scale is often different than most because I have my own bulldozer. So when I was thinking big craters, I was thinking craters a half acre in size or more. Now that would be too big, but the size you mention would be perfect.

My swales are about 8 feet wide because my little bulldozer has an 6 way blade perfect for making swales, and so the end up being that wide. It takes about three passes to make a good swale; two to shape the up slope and then 1 on the back slope.  My bulldozer pitches 8 inches in 8 feet, so its a pretty steep in-slope, obviously a steeper out-slope, and with that much material being delivered there, I would say my swales average 3 feet deep. I say average because it all depends on what I am cutting through in order to move/retain water. Still my calculations show about 150 gallons of water per linear foot of swale. Not bad considering.

I think the prevailing wind has a lot to do with snow collection and retention just because it is to the North, and as anyone in Maine knows the Northeast is where you get your heavy weather and high winds. The snow blows across ample open land, collects in the swale and then gets trapped there.

Personally, I'm interested in both sized craters. The small ones I will definitely experiment with first because they are easy and I can dig out several in an afternoon with my backhoe. The larger style ones probably fall more into the "it sounds cool and I'd love to try it out" realm, but my little backhoe would be a poor choice of tool for this job.

I like the idea of craters, but think a big one would defeat the purpose. You want the wind and air to pass overhead, the interior filling with snow. Too big of a crater would defeat that.

I've been thinking about this for a couple days, and it's an interesting point due to the circumstances of how snow flows in my property. I feel fairly confident that in mid-winter I'd be able to fill up at least a 10' deep crater, and I suspect closer to 20'. Three weeks ago, I measured 7' of snow on the ground, and my 4-5' deep pond I dug out in the fall was totally flat (invisible). What ends up happening is that snow from the surrounding mountain (adjacent, 1000' higher, and much cooler) blows around, gets trapped by smaller hills, blows around and fills in the meadow like water. So while there may only be 1-2' of snow on the hillside 20' above the meadow, the meadow can still be 7' deep.

That being said, this will be the first year I watch the snow melt. I am not sure if larger craters would trap the cool air and maintain snow for longer, or just provide a slope for the warm melt-water to rush down and melt even more snow. Spring tends to come fast here and it seems that snow tends to remain where it's shady rather than where it was deeper.