13 Cover Crops You Should Plant in September
You don’t have to be a full-fledged farmer to benefit from the use of cover cropping. You can use these plants to rejuvenate any garden bed over the off-season. Join gardening expert Melissa Strauss to learn some of the best options for boosting the nutrients in your soil for next season.
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You might picture a considerable farming operation when you think of cover cropping. Cover crops are also a great tool for home gardeners. There are cool-weather crops and warm-weather crops. We focus on those that aid the soil during the cooler months in September.
Of course, cover cropping is a great tool for rebuilding and maintaining the soil in your vegetable garden. Did you know this process is also helpful for annual beds that need rejuvenation? Let’s talk about the function of cover cropping and some plants that you can plant in September to enrich your garden for next spring.
What Are Cover Crops?
Cover crops are plants that we rotate between planting other crops that improve the soil in specific ways. We typically plant them after a harvest and leave them in the ground until we are ready to plant the next crop. They are often chopped and dropped on the soil surface before they can go to seed.
Most, but not all of these plants are annuals, which are then mixed into the soil or used as mulch for the next planting. Some, however, are perennials that you can either mow before they flower or use as a more long-term solution.
What Purpose Do They Serve?
I’m so glad you asked! Cover crops are a valuable resource that serves important purposes in terms of soil rejuvenation. Each one has its own functions. Some of the reasons to use them include:
Improved Soil Health
Cover crops improve the structure of the soil and provide aeration. Living roots help to maintain nutrients in the soil and support microorganisms. These plants also help to rebuild the soil when broken down and incorporated into the soil.
Some plants are nitrogen-fixing, which means they draw nitrogen from the air and deposit it in the soil. This helps to replenish the nitrogen lost to heavy feeders during the growing season.
Erosion Prevention
Another benefit of crop rotation using cover crops is the protection of soil from erosion. These plants don’t only cover the surface of the soil protecting it from rain and wind. The roots also improve the structure of the soil and encourage improved water infiltration.
Weed Suppressant
Cover crops serve as a weed suppressant in more than one way. Some are allelopathic, meaning they produce chemicals that stunt the growth of other roots and germination of seeds. They also block the sun, which prevents seeds that need light for germination from sprouting.
Money and Resource Conservation
For farmers, no-till cover-cropping methods conserve fuel used to till their fields. This saves money and is better for the environment. On a small scale, there is a benefit for gardeners who don’t want to spend time and energy tilling.
Support Grazing Animals and Pollinators
Many of the plants used this way are great food for grazing animals. Some also flower, producing valuable food for pollinators during the off-season. This keeps pollinators nearby, which is ultimately great for your harvests.
Best Cool Weather Cover Crops
Some plants work better for this purpose in the summer, between warm and cool weather crops. Others are ideal for planting during the cool season to replenish after the summer growing season.
Here are some great cover crops to plant in September. In warmer regions, you may want to wait another month to get started, as most of them prefer cool weather to do their most robust growing. Note that some are invasive in certain areas, so check with your extension office to ensure you plant non-invasive crops.
Winter Rye
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botanical name Secale cereale |
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sun requirements Full sun |
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height 2’-6’ |
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hardiness zones 3-7 |
Winter rye is cold hardy, and does a great job of protecting your garden over the winter. If you establish this cover crop in September, it grows far into the fall, and after a brief dormancy, resumes growth in early spring. It’s also easy to grow and requires little maintenance.
Winter rye is allelopathic, so it prevents weed seeds from germinating. It scavenges nutrients from the earth, which keeps them in your yard rather than washing them away. It has deep roots that help to prevent erosion and aerate the soil.
Daikon Radish
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botanical name Raphanus sativus var. longipinnatus |
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sun requirements Full sun to partial shade |
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height 8”-36” |
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hardiness zones 2-11 |
Daikon radishes are a fantastic root vegetable that works great for protecting and enriching beds over the winter. They repel pests and suppress weeds, making a lighter load for the gardener in spring.
They recycle nutrients in the earth by capturing excess nitrogen. When they decompose in the spring, that nitrogen goes back into the ground. Daikon radishes have deep taproots that are also great for breaking up compaction.
Winter Vetch
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botanical name Vicia villosa |
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sun requirements Full sun to partial shade |
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height 1′-3’ |
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hardiness zones 3-9 |
Winter vetch is a nitrogen fixer, so it provides nitrogen to next year’s vegetables. It also helps to retain moisture in garden beds. It grows quickly, forming a mat that prevents erosion well.
There is research that suggests that vetch can improve the disease resistance in your garden. Use it as mulch in the spring to protect your newly planted crops. Its mat-forming growth also does a great job of preventing weeds.
Fava Beans
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botanical name Vicia faba |
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sun requirements Full sun |
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height 2’-6’ |
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hardiness zones 2-11 |
Fava beans are one of the top nitrogen fixers, and their deep roots are excellent for improving belowground structure and aeration. They will break up clay and other compacted earth while they deposit nutrients.
These beans are great for weed suppression, and flower in spring to provide food for pollinators. They are highly cold-tolerant, and they are edible to boot!
Cut them at the surface and leave roots to decompose when in bloom. Use the tops as mulch for an excellent nitrogen boost.
White Clover
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botanical name Trifolium repens |
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sun requirements Full sun to partial shade |
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height 4”-12” |
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hardiness zones 3-10 |
White clover is a great cover for higher-traffic areas. It’s resilient, sturdy, and cold-tolerant. It’s also favored by grazing animals and honeybees. You can use it between rows of other plants to act as living mulch and weed suppressants.
Plant this cover crop in September and help prevent erosion. Clover has a thick, interconnected root system that breaks up compacted earth and holds everything in place. Clover is nitrogen fixing, as well, although it’s not as effective for this purpose as other legumes are.
Crimson Clover
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botanical name Trifolium incarnatum |
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sun requirements Full sun |
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height 1’-3’ |
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hardiness zones 3-9 |
Crimson clover does extra duty as a beautiful ornamental. The scarlet flowers that cover this mat-forming cover are wonderful! It creates a home for beneficial insects, so it’s great for pest control. It’s also great for grazing animals.
Like other clovers, crimson clover is a nitrogen fixer. Its roots are good for improving soil structure and preventing erosion. It also helps to control weeds in the spring.
Mustard
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botanical name Brassica nigra |
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sun requirements Full sun to partial shade |
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height 3’ |
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hardiness zones 6-9 |
Mustard is a wonderful winter leafy green vegetable. It’s also great for rotating with other, warm-season veggies. Mustard releases chemicals into the soil that help to repel pests and damaging pathogens below the soil surface. Biofumigation is the term for this process. It can also repel some weeds.
Mustard is a fast grower, and it likes cool weather, so it covers the ground quickly and completely. It scavenges nutrients that you can feed back into the earth in spring. You can also eat mustard; it is a big biomass producer, so it’s a great energy source for us!
Cowpea
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botanical name Vigna unguiculata |
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sun requirements Full sun |
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height 18”-36” |
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hardiness zones 10-12 |
Cowpea is an excellent nitrogen fixer and adds organic matter to your beds as well. They are drought-resistant and easy to care for. This fast grower blocks out weeds and helps to improve texture and aeration.
This flowering plant provides important nutrients for pollinators and other beneficial insects. By feeding insects like lady beetles and bees, you can keep them close for all the work they perform in the growing season. It’s a decently cost-effective plant as well.
Oats
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botanical name Avena sativa |
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sun requirements Full sun to partial shade |
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height Up to 5’ |
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hardiness zones 2-7 |
Plant oats together with legumes to boost legume growth. Oats make great mulch to insulate next season’s crops. They also contribute to softening and loosening the earth, which means better root development for the next residents.
Oats are great for preventing erosion, and they act as a weed suppressant. They are vigorous growers that will out-compete weeds for nutrients and water, so they’re good for keeping intruders to a minimum.
Winter Wheat
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botanical name Triticum aestivum L. |
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sun requirements Full sun |
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height 2’-5’ |
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hardiness zones 10-12 |
Winter wheat is a cereal grain like oats and rye. It’s great at scavenging nutrients that you can put back into the soil when you chop it and drop it. It’s less expensive than many other cereal grains, so it’s popular as a result. It’s slower to mature, and it’s easy to grow.
Mix wheat with crimson clover; the two complement each other, and the clover feeds the wheat. Winter wheat is a good weed suppressant and helps to improve water conservation.
Berseem Clover
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botanical name Trifolium alexandrinum |
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sun requirements Full sun |
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height 18”-30” |
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hardiness zones 6-12 |
Berseem clover is popular for rotating with crops that are nitrogen demanding like corn. It is an excellent nitrogen fixer, and probably the best of the clovers for this purpose. Animals like to feed on it, and pollinators are also fond of the flowers.
In addition to its nitrogen-fixing capabilities, berseem clover covers most of the bases. It’s a good weed suppressant and a vigorous grower. It has an intricate, fibrous root system that helps hold the earth together and prevents erosion.
Alfalfa
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botanical name Medicago sativa |
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sun requirements Full sun |
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height 2’-3’ |
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hardiness zones 3-8 |
Alfalfa is one of the most popular and widely used cover crops, perfect for September planting. If you have grazing animals, this is a great forage for them. It’s highly digestible and a great source of protein. Alfalfa residues also help compost to decompose faster, maintaining higher nutrient levels in the compost.
Alfalfa breaks down quickly in general, so it’s great mulch. It helps to improve the structure of the soil, prevent erosion, and enhance nitrogen fixation. It’s beneficial to pollinators and other wildlife. It’s overall a very well-balanced option. Chickens benefit from alfalfa supplementation in their diet.
Austrian Winter Peas
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botanical name Pisum sativum subsp. arvense |
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sun requirements Full sun |
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height 2’-6’ |
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hardiness zones 5-12 |
One of the primary benefits of Austrian winter peas is their cold tolerance. Hardy down to 0°F (-18°C), they survive well into the winter, sometimes throughout. They are legumes, which means that they are superior nitrogen fixers.
Austrian winter peas are good producers, so they provide you with a lot of organic matter in the spring. You can broadcast sow the seeds, which is convenient.
On the downside, Austrian winter peas may attract deer to the garden. If you don’t mind feeding the deer, that’s no big deal, but you don’t want them eating next year’s veggies. It’s also a thirsty plant and needs regular watering.
