High Altitude Gardening: Pre-warm your garden boxes
Don’t these warm spring days make you anxious to garden? How about getting a jump on your vegetable garden. I’ll bet you’re thinking, “No way! The ground is still frozen.” But with a few special techniques, you can start garden planning — and planting — as soon as the snow melts from the valley, which this year, is about now.
Mostly, I love the excuse to be out on a beautiful, spring day, if I’m not skiing. But there is one drawback to early gardening. We call it “mud season.” As soon as that spring sun hits the ground, and the day temps reach above 40, the top inch or so of dirt starts to thaw. And attempting anything in the garden may only get you boot-loads of mud to track in the house.
Start the day a little earlier, when the ground is still frozen in the morning. Hopefully you have built a system of garden beds called raised beds, surrounded by paths or lawn. Raised-bed gardening is the system that can be most efficient and productive for high altitude gardeners. Raised beds are simply growing beds that are surrounded by timbers, or boards, to hold the dirt in, above the surrounding ground level. Being raised above the surrounding ground level, these beds warm up faster in the spring for planting, and maintain a warmer temperature through the season. Soil temperature, more so than air temperature, is what determines the growth rate of vegetables.
So before the ground thaws in the morning and turns to mud, have large sheets of clear, plastic visquine ready, and cover the entire bed, holding the plastic down with staples, or rocks, as securely as possible. This creates a mini-greenhouse effect over the frozen soil. Within a week or two, the entire bed will be warm and ready to plant with cold-season vegetables. Even if there are still snow days in April or May. A thermometer in the soil will show the day-time temp under the plastic can reach above 100 degrees in the sun.
The next step, once the soil is thawed, is to turn in about 3 inches of compost and mix well with your soil down to 6 inches. Any bagged compost from a garden center will do. Depending on the weather, cover the beds again with the clear plastic and warm (or cook) for another week. The mini-greenhouse will cause any weed seeds to pre-sprout so they can be easily pulled before planting. But the warming will also promote the natural composting action of the bacteria in the soil, which helps to enrich the soil for healthy, growing veggies. Garden beds can be ready to plant as early as April 1 in Eagle or Edwards, and there are many veggies that don’t mind the cold and spring snow through May. Depending on your elevation, any of the hardy, leafy greens, like arugula, kale, spinach, and bok choy, can be planted when the snow is still falling in April or May. As soon as the days are consistently above about 50 and nights stay above about 25 degrees, these hardy veggies will sprout, and grow as the days get warmer. Be careful to remove the plastic covers during the warm days so you don’t cook your new sprouts, and cover again at night help keep them warm.
By planting in April, and using some protections — like plastic covers or cold frames (glass covers) — I can have fresh, organic, spinach ready to harvest by June 1. Higher elevations like East Vail and Wildridge may be 1 to 2 weeks later.
We will learn more about High Altitude Gardening, plus many other tips like how to construct raised beds, and build a healthy soil, and how it will help build a more sustainable community, in my High Altitude Gardening Class at Colorado Mountain College on Wedesday, April 9. For more info contact CMC in Edwards or call Lori Russell, 970-328-5324.
Lori Russell is a local gardener, professional landscaper and teacher of high altitude garden techniques at CMC. She lives and gardens in Eagle Colorado.