Cover crops are a confusing topic for most gardeners, and no wonder. Most books expect you to plow them under. To gardeners, that doesn't sound doable. But new research shows that soil-building comes easier than that: from roots.
Of course, the top growth is important; preventing weeds alone is a huge benefit. And preventing soil loss. But out of sight, the roots do much more. Like opening passages for oxygen, feeding earthworms--and dying.
When the tops are cut, the roots die and turn to compost right there in the soil. Compost that you don't have to haul, turn, or shovel. And we aren't talking small amounts here. Winter Rye makes 380 miles of roots per plant. The most fertile soils in the world are grasslands, where the roots grow and die in the soil year after year.
What to Plant? Let Nature be your guide.
Meadows and prairies have a mixture of grasses, legumes, flowers, and taprooted plants. The famously fertile topsoils of the Midwest were built by such plant communities. Use that soil-building synergy in your garden. Your mix should include:
Timing is important
The size of the root system depends on when you plant. It's best to sow cover crops 2-4 weeks before your first fall frost. * Don't be surprised if the plants don't get tall--they will be busy underground. In tests, crimson clover that was was only 2 inches tall by November nevertheless had roots 12 inches deep, with many nitrogen nodules already fertilizing the soil. Rye only 6 inches tall had roots 20 inches deep. All winter, the roots will be holding your soil, providing channels for water absorption, and adding tons of organic matter to your garden.
But how can you plant cover crops when the beds are still full of summer plants? Here are some options:
Don't forget pots and containers.
A low-growing, cover crop prevents your expensive soil mix from getting washed away or taken over by weeds. Calendula, poppies, salad greens, clover, and peas are great for this. If you aren't using the pot, cover it with its saucer to keep weeds out.
*You can find first and last frost dates online. Here is one place:
Jamie Chevalier lives and gardens on a river in the Coast Range. She has gardened professionally in Alaska and California, as well as living in a remote cabin and commercial fishing. She wrote the Bountiful Gardens catalog from 2009 to 2017, and now is proprietor of Quail Seeds.