Crimson clover growing in the wild. Growing crimson clover in empty vegetable beds adds nitrogen to the soil and attracts pollinators, too.

Crimson clover growing in the wild. Growing crimson clover in empty vegetable beds adds nitrogen to the soil and attracts pollinators, too.

Seems a bit late to be planting anything in the garden right now, doesn’t it? Yet early fall is exactly the time to sow the seeds of cover crops in your empty vegetable beds, so they have time to germinate and grow before frost.

Cover crops are plants that are grown, not to be eaten, but to be cut down and incorporated back into the earth. This plant matter improves the health and structure of your soil by adding back some of the nutrients that were taken up by the vegetables in those beds. In addition, they improve the tilth of the soil and increase its capacity to hold moisture.

Also called a living mulch or green manure, cover crops are best for in-ground and raised beds where spent plants are removed and the soil would otherwise lay bare all winter. The clippings act as mulch, breaking down over time, and the roots keep soil from eroding or blowing away in winter storms and winds.

If you clean out your vegetable beds leaving only bare soil, it won’t be bare for long. Nature abhors a vacuum, and weeds will soon make an appearance. Cover crops are a natural weed barrier.

It is an easy, inexpensive and less labor-intensive way to enrich soil that doesn’t involve shoveling or dragging around heavy bags of amendments. While not entirely labor-free­--you still have to dig the plants into the ground so they can decompose--it’s an easier job.

Cover crops can also solve problems in your soil, whether it’s low nitrogen, compaction or erosion:

To increase nitrogen: Plant legumes such as peas, vetch, alfalfa, or red or white clover.

To break up hard soil: Winter rye and winter wheat have extensive root systems that help break up clay soil. Daikon radishes also help with hard, compact or clay soil, plus they’re edible.

To control erosion: When the root system is left in the ground, pretty much any cover crop helps control erosion, but the roots of clovers, winter rye and winter wheat are especially dense and effective for this purpose.

To cover soil fast: Try quick-growing buckwheat, oats, annual ryegrass or winter rye.

Cover crops suited to fall planting include oats, winter wheat, vetch, winter rye and medium red clover. These last three are perennial and will grow again in the spring.

Others, such as buckwheat, crimson clover, and white clover do better planted in warmer weather. When planted in spring, the flowering cover crops, such as the clovers, buckwheat and alfalfa attract pollinators. More pollinators mean better pollination rates for your flowers and vegetables.

Cover crop seed is sold in bulk, like grass seed, not in small seed packets like vegetable or flower seeds. It’s available as a single species or as a seed mix. Find it at garden centers, farm supply stores and from online seed companies.

When it comes to timing, check the first frost date for your area against the days to maturity for the cover crop you want to grow. Then count backwards from the frost date to determine when to sow the seed.

If using a legume such as peas, clover or vetch, first treat the seeds with inoculant to help fix the nitrogen in the soil.

Rake the area to be planted so it’s level. Broadcast the seed over the soil, and gently rake it in. Water using a fine mist or gentle spray, not a strong spray that could dislodge the seeds.

Then sit back and wait for the seeds to germinate, watering regularly if there’s no rain. You might have to pull a stray weed, but, other than watering, there’s nothing to do but watch it grow.

You can cut or mow the cover crop down around your first frost date, or once the cold has killed the plants. Cut the top growth off (hedge shears work great for this) so that the clippings fall on the ground. Leave the stalks and roots in the soil to prevent erosion through winter, and dig them into the ground in spring.

Or let the entire plant stand through winter, then cut it down and till it under in spring, at least two or three weeks before you plan to plant. Dig the plants and/or clippings into the soil, so they have time to decompose.

Another option is to simply plant your vegetables, leaving the clippings and plant residue as a mulch. This only works with cover crops that completely die back, such as peas and annual grasses.

Cut the cover crop down before it goes to seed, or you may end up with a second cover crop without intending to.

Cold frames protect plants from the worst cold weather, and are roughly 5 to 10 degrees Fahrenheit warmer than the outside air, helping gardeners grow beyond the traditional growing season.

Cleaning up the vegetable garden at the end of a growing season is one of the most important tasks that gardeners can do to set themselves up for success the following year.

When is the best time to plant garlic? What’s the difference between softneck garlic and hardneck garlic? A Penn State Master Gardener offers tips on growing garlic at home and protecting your harvest from pesky allium leafminers.

Therese Ciesinski is an award-winning garden writer and editor.

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