It won’t be long before we’ll be into short sunshine days, days in which the sun shines less than 10 hours each day. That will start about the first week of November and last until early February. During that time, plants grow very little, if at all.
So if you’re going to plant for early spring lettuce, spinach or any other frost-tolerant crop, I think it’s best to at least get seeds germinated before the onset of winter cold and drear. Tiny seedlings may withstand freezing better than older plants. Planting cover crops now is especially important, at least to get root development started. You don’t need to pull spent plants after they’ve been killed or have stopped producing, just cut them off just above soil surface. As their roots decay in soil, that adds to organic matter in your soil too. In spring, when you’re ready to plant, pulling those stubs is easier than pulling them in fall and minimizes disruption of the microcosm in your soil.
In the past I and other gardeners have waited until we closed out our producing gardens before planting cover crops. That’s not necessary. Undersow cover crops now, even among your producing upright plants. Clover and vetch seeds don’t need the sun exposure that grains need for germination. Some cover crops such as winter peas or vetch will spread to cover gaps in your seeding. The root development that breaks up and softens your soil (and adds organic matter) is most important. For instance, a test of crimson clover, 2 inches tall by November had roots 12 inches deep according to Bountiful Gardens, and since it’s a legume, that clover had taken nitrogen from the air and fixed it on nodules on its roots, ready to fertilize the next crop to be planted there.
Some experts advise planting cover crops four weeks before the first expected frost, not the two weeks we have remaining if frost arrives on that date (Oct. 6). The past few years have made anticipation of first frost a true shot in the dark, however. We used to have a sharp frost for a night or two, then a few weeks of “Indian summer” before hard freezes. In recent years we’ve had extended warm weather far past the early October date, then a sudden steep drop in temperature. That’s been hard on humans, plants, trees and shrubs.
What do you plant for a cover crop? At the least, the cover crop will preserve your soil from erosion and from being compacted by rain and hail. Deep-rooted winter crops can bring minerals up to the usual root zone from deep in the soil, while improving air- and moisture-holding capacity of the soil. Some crops such as large radishes (daikon, for instance), left in the soil to decay, break up heavy clay. Most fall-planted cover crops feed earthworms and micro-organisms in the soil, and some even produce nectar, attracting pollinators to your garden bed.
In selecting plants for cover crops, pay attention to the winter temperature that will kill the crop. Our lowest expected winter temperature is 0 degrees F., according to the USDA, but right after they decided on that zone for us, our winter low dropped to minus 10 degrees F. If plants have had a good chance to grow before being winter killed, you’ll enjoy some of the benefits, at least. Also consider how you’ll dispose of this cover crop when it’s time to plant anew. Some vetches are very difficult to remove, and some cover crops are most beneficial if allowed to grow until late May.
In this area, we usually start planting spring crops such as lettuce, spinach, onions, brassicas, peas and potatoes, etc., in March, around St. Patrick’s day, unless we started lettuce and spinach the previous autumn.
Zamzow’s stores are selling “Green Manure Seed Mixture” cover crop seeds in 2-pound bags, containing seeds for winter rye, annual ryegrass, buckwheat and crimson clover, so you don’t have to select or decide what to plant. D&B Supply has 5-pound containers from Garden Way, with seeds for winter peas, winter oats, crimson clover, gulf ryegrass (an annual) and common vetch. Peas and oats could be harvested if you don’t remove them for early planting.
Send garden questions to firstname.lastname@example.org or Gardening, The Statesman, P.O. Box 40, Boise, ID 83707.
This has been a poor year for tomatoes, although the temperatures have not been disastrous for pollination. I suspect diffused sunlight through smoke through much of the summer is to blame.