Vail gardening column: The advantages of using a frost cover in your garden
High Altitude Gardening
So how’s your garden growing? This cold, snowy and rainy spring is enough to discourage the heartiest gardener. But it is not unmanageable. Most of the greens that I planted a month ago (at the end of the warm spell) in April, are growing, albeit slowly, and are about 1 to 2 inches tall now. They are off to a good start and with the next warm rays of sun, they will take off.
Meanwhile, my potato foliage is already reaching a foot in height, despite the frosty nights. The photo shows my potatoes, with radishes and beets planted between the rows, all cozy under a frost cover blanket. I will probably have an early potato harvest this year, and bok choy will be ready in early June. The biggest secret is using a few techniques to manage our cold high-altitude nights.
RAISED GARDEN BEDS
The first thing is to plant in raised beds, built above the surrounding terrain with 2-inch-by-8-inch boards, or just rocks. Then, as soon as the snow melts — and after you’ve added compost — cover the raised beds with clear plastic (not black plastic) for a week or two in the early-spring sunshine. Weigh the plastic down all around to create a mini-greenhouse. This will warm the garden soil, which is the most important factor in getting seeds to sprout! The surrounding ambient soil may still be 35 degrees, where nothing will grow. But your raised bed can be warmed to 50-60 degrees, perfect for sprouting most of the early greens. The early greens, like kale, spinach, radishes and bok choy, don’t mind frosty nights down to 25 degrees, as long as the soil is at least 50 degrees.
Potatoes are a bit more sensitive. The potato seeds do fine under the warm dirt, but the leaves that sprout above the ground will be wilted by frosty nights. So you must use your next line of defense: frost covers. This is a light, white, insulating cloth that can be purchased from garden suppliers like Farmtek.com. Like a white sheet, but easier to use, this white cover is spread over plants in early spring and late fall to protect plants from frosty nights. The temperature inside the frost cover can be 5 to 10 degrees warmer than the outside air, protecting plants from freezing when the night temps hover around 35. They may not save plants if nights go below 25 degrees, so wait to plant until nights are mostly above 30 degrees. In Gypsum and Eagle this can be as early as April, but in Avon, it may not come until May, and June 1 in Vail. It is altitude dependent. Check your weekly forecast every day for predicted nighttime lows. Or set up your own outdoor thermometer and check it every morning before sunrise to see the trend.
The other advantage of frost covers is that they can be left in place day and night, like a mini-greenhouse that allows daily rain to penetrate and the plants to breathe. In warmer climes, they are used year-round to protect plants from bug invasions (we don’t have many bugs at high altitude).
One of the biggest challenges to early season gardening is getting water to your garden. If you run a hose (automated sprinkler systems are still off), you have to be sure to disconnect and drain it each time, so it won’t freeze your hose bib at night. I also keep a filled bird bath by my garden hose, which can tell me how hard the nights are freezing. If it’s still too cold, wait for warmer nights and water during the warm hours of the day. During the cool, moist spring, you may only need to water once a week. The cold-hardy seeds and new sprouts won’t mind the cold nights. And they will be even happier and warmer with frost covers.
Lori Russell is a local gardener, a professional landscaper with All Seasons Service and teaches high-altitude gardening techniques at Colorado Mountain College each spring. She lives and gardens in Eagle. Email comments about this column to firstname.lastname@example.org.