Leaving bare soil in your landscape is not a good idea. Bare soil is subject to erosion from water run-off, it can starve beneficial organisms in the soil, and it creates a perfect spot for weeds to germinate. There’s still time for you to plant cover crops to protect those bare spots.
Hopefully, you’ve mulched the soil where plants are already growing – around trees, shrubs and perennials for example. But what about bare spots in the lawn, annual beds and vegetable gardens?
For bare spots in the lawn, it’s best to seed them with a mixture that will blend with the existing lawn plus a healthy amount of annual rye. Annual rye germinates quickly and is very cold tolerant. It will also protect the other seeds in the mixture that take longer to germinate and are less cold hardy. The rye will grow for only a year and then die off, leaving the perennial grasses in the mixture to live on their own.
You have several cover crop options for large, bare areas like annual beds and veggie gardens. Take a lesson from the agriculture community. Farmers select cover crops for the dividend they’ll pay in terms of benefitting the soil. If the soil needs nitrogen, they’ll plant legumes like beans, peas or clover. Otherwise they are more apt to plant a grain, with rye being the most popular.
For the home gardener, crimson clover is a popular legume. Like all legumes, crimson clover has nitrogen-producing bacteria in its roots. When the plant dies, it leaves fixed nitrogen in the soil. Crimson clover produces an attractive red flower that makes your garden look nice while its roots are holding the soil in place and fixes nitrogen.
When the nitrogen-fixing benefits of legumes aren’t needed, annual ryegrass is a good cover crop choice. It’s fast growing, not unattractive and compostable in spring. If you don’t mow the rye grass in the planting beds, you can just pull it up in spring and put it on the compost pile. During the winter, the grass roots feed beneficial microbes and any plants that died decomposed, returning nutrients to the soil.
Mustard is another cover crop used by some gardeners. Its roots release chemicals into the soil that suppress weeds and soil borne pests. Good soil is, arguably, the most important factor in successful gardening. That’s why so much time and money is spent applying fertilizer and soil amendments. Planting cover crops to protect bare soil yields many of the same benefits during the season when the soil isn’t being used for other purposes.
One of my favorite cover crops had been that old fashioned big and weedy zonal geranium with the bright pink flowers. I know it gets big, but it excludes weeds and conditions the soil. It can last for a few years if I just cut it back after winter. The only problem is that it generates so much vegetation, and gets mushy if piled too deeply on compost. (I just toss it onto areas that are overgrown with other weeds, like chips.)