I am so happy that part of my job is to be “In The Garden.” I feel like it’s a great privilege and responsibility to take what I learn in my garden and turn it into something useful for your garden. Sometimes, excitement and enthusiasm are just as useful as tutorial information. Well, this week I have both. The weather has been really great here in the Front Range of Colorado. Sun, mild temperatures, and longer days have all conspired to make some great gardening opportunities. I won’t let the fact that there’s a snowstorm on the horizon dampen my spirits. Everyday I go out into my garden and walk around. I look at what’s going on and dream about what’s to come. But what I’ve seen lately has me bubbling over with excitement. I see springtime – maybe not full-blow emerald-colored life pushing out of the earth, but the signs are there. Tulips and early alliums, like shallots, garlic, and chives, are forming conspicuous green clumps around the landscape. Maroon domes of emerging rhubarb are undulating out of the ground, and the buds are swelling ever so slightly on fruit trees. I even have some Monstrueux de Viroflay Spinach that made it through the winter! If these wonderful events haven’t happened to you yet, they will soon.
My excitement about the situation at hand has turned my efforts towards helping the season advance quicker, or at least not regress back into winter. How do I go about this? Soil warming. Why? Soil temperature governs the rate of seed germination and root growth. If we can warm our soil sooner, we can start gardening sooner! There are lots of things you can buy that are specially designed for this purpose and lots of creative ways to achieve this by reusing or re-purposing items around your house. Let’s look at a handful.
Lots of folks are familiar with Wall-o-Waters, Tomato Teepee, or Kozy Coats. Whatever the name, the idea is the same. These specially made products create protective jackets for warming the soil and protecting plants inside them from frost. They do this by employing the thermal capacity of water. Sounds fancy, but they’re simple and they work. They are usually marketed for tomatoes and other warm season vegetables, but you can use them for much more. Once they’ve been set up for about 10 days, the soil starts to stay reliably warmer. I’ve had mine set up for about 2 weeks now. While I plan to have tomatoes in them later in the season, I will sow spinach and peas in them now for a super early crop.
A traditional approach to soil warming is cold frames. If you are not familiar with these, think of them as tiny greenhouses placed over the soil. They are often employed to harden seedlings for transplant or to offer protection to tender plants in the early season, but if left in one place long enough, they warm the soil well and allow it to be planted much sooner. The cold frames of my childhood were made from old windows screwed together into an open-bottomed box. This still works great, but you can be creative with the design. Any clear covered box will do. It traps heat like a greenhouse and allows the plants inside to get the light they need to grow.
Even if you don’t plan to sow or transplant early, warming the soil up until your standard sowing times will add great benefit. When you do finally decide to populate your garden, you will have warmer soil that helps seeds germinate quicker, transplants establish faster, and everything produce and flower faster. That all sounds great right now while I wait for the gardening season to hit full swing. If this is something you want to try, you don’t have to do it over your whole garden. It still works if you do it a little at a time. I’ve seen lots of methods work, too. Milk jugs or 2 liter bottles filled with water placed over the soil help warm and insulate it. Try putting some dark food coloring in the water to trap more heat (I like blue mixed with red).
Lots of farmers use black plastic film or fabric to warm the soil, and you can, too. Just remember to remove it at the end of each season. Even those old black nursery containers flipped over with a rock to weigh them down will trap heat during the day and store it in the soil. Try watering dry soil before warming it; wet soil holds heat better.
I think writing this has made me even more excited. I’ll be outside planting Super Sugar Snap Peas and Monstrueux de Viroflay Spinach while you read this. When you’re done, maybe you’d like to try warming up your own soil and drawing your growing season a little closer.
Ryan The Horticulturist