As the vibrant colors of autumn gradually yield to the tranquil serenity of winter, the diligent gardener's work is far from over. While most plants hibernate, and the world outside seems to slow its pace, the savvy gardener knows this is the perfect time to enrich the soil, protect it from erosion, and prepare for a bountiful spring harvest. Enter the world of fall and winter cover crops—a hidden treasure in the gardener's toolbox that ensures your garden remains a thriving oasis year-round.
In this comprehensive guide, we will explore the fascinating and often overlooked realm of cover crops, unveiling their secrets to success for gardeners.
What is a Cover Crop?
A cover crop is a crop that is planted for the purpose of keeping bare soil covered, to prevent soil erosion, and to improve overall soil fertility. Unlike planting vegetables or fruits, cover crops are not meant to be harvested. Think about it; all summer long, the vegetables you've planted are devouring all those precious nutrients and micronutrients from your soil, storing nutrients into the beautiful and delicious harvest that, after a few months, will end up on our plates and in our bellies.
Year after year, if you are planting in the same bed and not adding back to the soil, it can become quickly depleted. This is not a new concept ~ in the late 1800's, Justus von Liebig stated that "the productivity of the soil alone has caused the rise and fall of nations, and, in a word, has made history." 1 That's where things like cover crops and composting come in.
Why Should I Plant Cover Crops?
In addition to adding compost to soil, planting cover crops is one of the best things you can do to help improve your soil, whether you're on a farm or an urban gardener! Here are some reasons why cover crops are awesome:
- They cover the soil when it would otherwise be bare, preventing erosion & compaction.
- They prevent nutrients from being leached out of the soil.
- They add organic matter (in the form of carbon) to the soil - which improves soil in countless ways! Organic matter is what gives good soil that rich, dark color that we all covet.
- Nitrogen-fixing legume cover crops like hairy vetch, peas, beans, and clover add valuable nitrogen to the soil.
- Deep-rooted cover crops can bring up nutrients from deeper soil layers. 6. They can help suppress weeds by shading them out and secreting allelopathic chemicals inhibiting weed growth.
As you can see, planting cover crops is one of the best things you can do to maintain soil health and fertility sustainably!
Pictured: Sugar Magnolia Pea (click for seeds)
Types of Fall/Winter Cover Crops
Fall/winter cover crops are planted in the fall and, if well established in the fall, survive the winter and begin to grow again in early spring.
The best two fall/winter cover crops for northern latitudes are hairy vetch and rye because they are very cold hardy.
There are a few different types of rye. The best for cold winters is called "Cereal Rye." You can also plant "annual ryegrass," but avoid "perennial ryegrass." Rye and vetch work well together: the vetch adds nitrogen back into the soil (it's a Nitrogen-fixer), while the rye prevents nutrients from being leached from the soil, prevents erosion, minimizes soil compaction, and helps prevent weeds. While rye and vetch can also be grown in the summer, we will focus on fall planting them in this resource.
When to Plant Fall/Winter Cover Crops
Sow winter cover crops in late summer or early fall. Be sure to get them planted by 9/30 or 10/15, depending on your latitude. You'll want to plant early enough for a good 2-4 inches of growth before winter arrives. Correctly planted, they will overwinter and grow vigorously in spring, suppressing weeds.
Why Inoculate Hairy Vetch Seeds?
For best success, inoculate hairy vetch seeds with a "Pea/Lentil/Vetch" rhizobium inoculant available online. Store the inoculant in the refrigerator and replace it every several years. This inoculant provides the "nitrogen-fixing" bacteria to help the vetch fix nitrogen. Hairy Vetch will grow without the inoculant but will be a better cover crop with it.
To inoculate your Hairy Vetch seeds:
- Inoculate your seeds just before planting.
- Put the quantity of seeds that you will use in a small container.
- Drop a couple of drops of water on the seeds and shake or stir to disperse water.
- Sprinkle a dash of inoculant on the seeds and shake or stir to distribute the inoculant.
- Your seeds are now ready to be sown.
How Do I Plant Hairy Vetch and Rye in the Fall?
Inoculate seeds if desired (see Why Inoculate Hairy Vetch Seeds)
Plant seeds directly into the soil, ½" deep, 2-4 inches apart. You can sow them in rows or "broadcast" seed them.
What Do I Do With Cover Crops in the Spring?
Come late Spring, when you want to think about getting vegetable seeds in the ground, there are a few ways to handle the cover crops after they've had the winter and early spring to help feed your soil.
You can "skim" to remove them by using a flat, sharp shovel to slice them off at the point of contact with the soil. Put the "skimmings" in the compost pile. Alternatively, you can cut them off at the point of contact with the soil using a sharp pair of shears (this will mostly kill the cover crops, but there will be a few plants that come back). Add finished compost to the garden bed and cultivate the bed as usual. If you choose this method, you'll be able to plant right away.
Alternatively, you can mow them and then incorporate them into the soil with a tiller. If you choose this method, you should wait 1-2 weeks to plant.
Pro Tip: if you want to prevent the cover crop from re-seeding, you should deal with your cover crops before they can produce seed.
1 Huntington, Ellsworth. "Climatic Change and Agricultural Exhaustion as Elements in the Fall of Rome." The Quarterly Journal of Economics, vol. 31, no. 2, Feb. 1917, p. 177, doi:10.2307/1883908