Rushing the Season: Warming Soil for Faster Crop Growth

Tomatoes growing on the vine

Is patience a virtue?

Some gardeners wait for the sun to gently warm the soil before they start their garden. Others are impatient.

They buy a greenhouse, force-feed their plants and rush the season while competing with friends and neighbours for the prize: the first tomato or the longest cucumber.

I am in the second group, except for the force-feeding. I would never do that.

Planning for an Early Crop 

In January, I start thinking of ways to push my crops. I remember Travis Kennedy, an urban farmer in Edmonton, Alberta, Canada. Kennedy rushes spring up north in his outdoor soil. And he doesn’t even have a greenhouse.

Using Soil Cables

“I have soil cables. I’ll dig a trough and lay the lines kind of all the way along- kind of an S. The soil radiates the heat at night. I am not really heating it – I’m just keeping the soil from freezing.”


Kennedy says the soil is a heat reservoir. When soil heats up, it holds the heat and then radiates the heat upwards. I know from experience, the warmer the soils, the more nitrogen is available to plants and the faster plants grow.

“You should have seen how many cantaloupes we had here last year… but you need the heat, eh? In Alberta [cantaloupes] will just sit there. They won’t grow. Every cantaloupe we grew? Took to market? They were gone.

Kennedy says he earned  $20.00 or more for each cantaloupe and I am shocked by the price. “Well it’s an Alberta-grown cantaloupe. When are you gonna see that again in your life?”

“You should have seen how many cantaloupes we had here last year… but you need the heat, eh? In Alberta [cantaloupes] will just sit there. They won’t grow. Every cantaloupe we grew? Took to market? They were gone."

So I seriously consider warming the soil inside my Greenhouse Garden.  Maybe I can grow cantaloupes even faster than Kennedy.

The greenhouse warms the air but seeds wait to sprout until soil warms up. If I add heating cables, maybe I will grow food faster.

Helpful Husband comes up with a plan and he is quickly in the car and off to the big box store. He comes home with something labeled “Roof and Gutter De-Icing Cable”. The obvious intended purpose for this product is for defrosting snow and ice off roofs and gutters. Helpful Husband is an Engineer and he declares this cable will warm the soil as long as we bury the thermostat portion of the line and keep the soil moist.

So I dig out the top 6-inches (15 cm) of soil and lay down the 80-foot long cable, snaking it back and forth along the length of the bed four times. Like a wile garden hose the cable tries to curl but the instructions are strict. Do not let the lines touch or cross over.  So I hold the cable in place at each end with garden bricks.

I take the soil temperature before I plug in: the soil is at 35 degrees F. – just above freezing. At this temperature early hardy crops like radish or arugula might sprout but heat-lovers like tomatoes, cantaloupes, cucumbers and beans require warmer soil. In two days the cables heat the soil to a stable 60 degrees F.

I discover the company selling Roof and Gutter De-Icing Cables offers an identical product online for warming soil.  Their soil product is called Wrap-On Gro Quick and they say the electric cables take the freeze out of winter. But I’ve already done that with the materials locally available.

I seed last year’s leftover radish and arugula knowing they will be up and out of the ground before I plant my tomatoes. Which reminds me: I need to order my tomato seeds today.

My soil is warm. I am set to grow. Let the seeds arrive and the games begin.

More from Donna

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You can also read Donna’s gardening books too!  The No Guff Vegetable Gardening Book and her just released Gardener’s Gratitude Journal:  Part Diary, Part Personal Growing Guide.