Those of us who contribute to this blog have been learning quite a bit about working with Colorado soils this year! We no longer feel confident (well we probably never did) picking up bags of “top soil” or manure or compost and adding them to our garden soils. (If you missed it, see Leslie’s terrific post on this topic: New Advice on Soil Amendments.)
Most gardeners feel pretty good about adding compost they’ve made themselves to their vegetable garden soils. In our area, though, we rarely encounter gardeners who have tried out another homemade soil amendment, cover crops or green manure. A cover crop is a plant that is usually seeded in early fall (mid-September is best in our area but you can plant through mid-October) and then watered so it sprouts and grows before the first hard freeze. If it gets tall, it is mown to keep it from going to seed. It goes dormant (or even dies) after a hard freeze, and it then provides mulch over the bed during winter and the roots provide aerated soil next spring when it is time to plant. (If it did not die and greens up in spring, it may have to be treated with herbicide or removed so it does not compete with your vegetables in the growing season.) Green manure is simply a cover crop that is hardy enough to survive the winter and is tilled into the soil in the spring. (Note that both cover crops and green manures can be planted in the spring if you have enough space in your garden to give up an area for the growing season to allow the cover crop or green manure to grow over the spring and summer.)
Why do this? In addition to many other benefits, cover crops help control and act as a mulch to prevent weeds during the growing season. Green manures can improve soil fertility and texture.
Some good choices for cover crops in the Pikes Peak area include winter rye (very hardy), Austrian winter pea, and hairy vetch. Visit your local garden center or agriculture/feed store for these varieties and ask for additional suggestions.
A few warnings – deer will enjoy munching on your cover crop or green manure plant. And for once – IT’S OK! Don’t worry about it as you aren’t wanting to harvest anything from these plants. They’re just helping you keep it mowed so it doesn’t go to seed. Seconding, you do not want these crops to go to seed! Otherwise, you’ll have many little rye or vetch plants coming up with your seedlings during the next growing season. Finally, if you are going with the green manure option, spade or till the plant into your soil about a month before you plant to plant or seed in the same area. This will give the plant material enough time to finish decomposing so it won’t be competing with your new plants for soil oxygen and other needed soil ingredients.
For more excellent information on cover crops and green manures, be sure to read Colorado Master Gardener GardenNotes #244 – Cover Crops and Green Manure Crops. It’s available at www.ext.colostate.edu/mg/gardennotes/244.html.
Submitted by Carey Harrington, Certified Colorado Gardener
Photo courtesy of Johnny’s Selected Seeds (www.johnnyseeds.com)