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Gardening in regions with a short growing season can be an adventure. There always seems to be another spring snowstorm around the corner! To take advantage of every possible growing day, we need to get our snow melted and garden soil thawed as quickly as possible.
We run a plant business here in New Hampshire, where our growing season is short, so it’s important to get seeds in the ground as early as possible. To this end, I tested a few common methods for melting snow and warming the soil. I hope my advice helps you with spring planting, too.
Melting the Snow in the Garden
First, I put down squares of black plastic, clear plastic, wood ashes, and coffee grounds and tested each for how quickly they melted the snow.
Clear and Black Plastic: On the few sunny and unseasonably warm days we had, Mother Nature did a better job of making the snow disappear than either of the plastics, which actually seemed to protect the snow from melting. I ended up with two snow squares that still haven’t melted!
Wood Ashes: Surprisingly enough, the wood ashes quickly melted right through the snow.
Coffee Grounds: The coffee grounds seemed to insulate the snow from the sun’s rays, like the plastic, which resulted in little melting.
Warming the Garden Soil
After the snow was gone, I moved the two squares of plastic to one of the frozen raised beds to gauge their warming effect.
This time, the clear plastic worked best, thawing the ground to 6 inches and heating the soil from 36° up to 56°F in 4 days!
The black plastic only got to 50°F, but still managed to thaw the ground down 6 inches.
The wood ashes only thawed down 2-1/2 inches in that time and warmed to 48°F.
The coffee grounds were 1 inch and 40°F.
My control patch, which had no help with warming other than the sun, was thawed 1-1/2 inch and warmed to 44°F—better than the coffee grounds!
Best Ways to Melt Snow and Warm Soil
Use wood ashes to melt the snow and then put down clear plastic to warm the soil. The clear plastic lets in the sunlight and UV rays and holds in the heat, allowing the soil to warm up.
One thing to note is that ashes will raise the pH of the soil (and add potassium), so if you live in an area that has soil with a naturally high pH, you’ll want to forego the ashes and wait for Mother Nature to do the melting for you. Learn more about how to test your garden soil.
In the vegetable garden, we always plan ahead in the fall and put up the where we will be planting the peas in the spring. This seems to act like a snow fence and prevents the snow from drifting deeply over that bed so it thaws out and warms up first. Good thing, since I am very eager to get those seeds in the ground!
The soil is still pretty cold, it was 45°F on the last sunny day, but dropped back to 40 today since it is cloudy and raw out. Looking back through my records, March 11 was the earliest I have planted peas in this garden, and I had to replant them on April 2 because of poor germination. It probably rushed the season, and the seeds rotted. Even though many seed packets say to plant peas as soon as the ground can be worked, the soil temperature really matters. At 50°F, it takes 2 weeks for the pea seedlings to emerge, at 60 degrees only 9 days, and at 77 degrees only 6 days.
Learn More
One old-time trick is to plant peas when the forsythia starts to blossom. See more clues of planting by nature’s signs.
Check out this video to see more ways to warm the garden soil.
Albedo is a measure of how much light is reflected off a surface. Clean snow reflects most light. Wood ashes absorb the sunlight to melt the snow. A similar effect can be achieved with dry sand or dusty soil (especially with low organic content). Gather it dry in a 5 gallon bucket during warm season, set aside until needed. It will not change the pH like ashes do.
If it's too early in the year, I would think so. I think there was something about that towards the end of the article where in a previous year, the soil was "workable" but still too cold for the peas. I think maybe waiting a day or so without anything on top of the soil and then taking the temperature again would work?
We used to put wood ashes on the icy patches in our driveway for traction, guess I know why now. Thanks for your experiment!! I can so understand trying to rush spring!
I have taken to starting my peas indoors. I can start 50 plants in a regular flat. they germinate better and once they are 4" high, can be planted outdoors. these plants can withstand a mild frost, but I usually place a light cover over them until they get established.