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9 Best Cover Crops for Raised Beds and Why to Use Them

A photo showing wooden raised beds with healthy plant growth.

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We spend months preparing and tending to our raised beds of flowers and vegetables. We make sure to use good soil, fertilize as needed and mulch to prevent weed growth and maintain appropriate moisture levels. So at the end of the growing season, we can just stop and relax, right? In fact, there’s more we can do to prepare for the future growing seasons: planting cover crops.

Cover crops serve many useful purposes, including increasing soil nutrients levels, improving soil texture and drainage, feeding beneficial insects and microbes, reducing the number of weeds and preventing soil erosion from moisture and wind. A few of the best cover crops for home gardeners working with raised beds include winter rye, buckwheat, clover, hairy vetch and cowpeas.

In this article, you’ll learn about 9 of the best cover crops for raised beds, why you should think about using them and how to plant and care for these garden helpers.

Let’s jump in!

RELATED: Eggplant and Thai basil are two great options for growing in your raised beds (especially after enhancing the soil with cover crops!). Stop by our how-to posts to learn the basics of raising eggplant or getting started with Thai basil!

What is a Cover Crop?

Cover crops are plants we grow not for a harvestable crop but rather to maintain the health of the soil for future plantings.

Bare soil is vulnerable soil, for several reasons:

  • Weeds can quickly take over
  • The soil can become compacted through drying out from harsh sun exposure
  • Beneficial insect populations can drop for lack of food and shelter
  • Soil can erode from wind or water
  • Essential nutrients can degrade or wash away

Instead of leaving the ground bare between planting seasons, a cover crop functions as a protective layer to your soil.

The cover crop’s root system prevents erosion and also breaks up soil compaction. The foliage wards off moisture loss, crowds out weeds and provides a welcoming home for helpful garden insects.

Also, the organic matter in cover crops is so high in nutrients that they’re often referred to as “green manure.” When you turn the plants under the soil in preparation to plant your edible crops, these nutrients mix with the soil to add richness and promote better soil structure for the long term.

You have several different cover crop plants to choose from, offering many varied benefits due to their growth patterns.

Cover crops consist of three families that have specific benefits:

  1. Broadleaves: Includes buckwheat and sorghum-Sudangrass. Excellent for fast growth and weed suppression.
  2. Grains: Includes winter rye, pearl millet, oats. Fine root systems break up soil compaction, typically tolerant of most soil conditions.
  3. Legumes: Includes clover, hairy vetch, fava beans and cowpeas. Adds nitrogen to the soil as part of their growing cycle, often provides a dense cover.  

Why are Cover Crops Good for Raised Beds?

It’s not too hard to see the concept behind cover crops: They literally cover the ground when it’s not in active use and protect it for the future.

But raised beds are pretty small to begin with. Do they really need a protective cover crop? Yes! Here are a couple of reasons to consider:

Preserves soil quality. One great thing about raised bed gardens is that you have complete control over the soil you choose to fill your beds with. This often results in wonderfully rich, light soil that makes for happy plants.

But filling a raised bed with top-quality soil and amendments isn’t cheap, and cover crops can be a great way to protect your investment over the long term.

Can increase populations of helpful insects and microbes. Because raised beds aren’t at ground level, they can lack the naturally occurring garden friends that in-ground gardens have. These little helpers reduce populations of garden pests and create nutrients and organic matter that plants need to thrive.

Beneficial insects/microbes not only help out in the garden, they’re also an important part of the local ecosystem. So anything you can do to help increase your numbers of beneficial insects and microbes is a good thing!

Best Cover Crops for Raised Beds Table

We’ll be getting into the details of our picks for the best cover crops for raised beds, but before we do, here’s table that gives you a quick overview:

Table comparing the differences between the best cover crops for raised beds.

Best Winter Cover Crops for Raised Beds

Winter cover crops grow and establish themselves during fall and winter. This gives them several months to do their work of breaking up clumpy soil, releasing nutrients and shielding bare soil until the spring planting.

For most home gardeners, winter cover crops are the most effective route for fixing long-term soil issues.

There are several great winter cover crops:

  • Winter rye
  • Oats
  • Hairy vetch
  • Fava beans
  • Clover

1. Winter Rye

A photo showing winter rye plants growing as a cover crop.

Family: Broadleaf

Benefits:

  • Highly tolerant of poor soil
  • Develops a fine root system that breaks up hard soil
  • Fast growth pattern produces an effective ground cover quickly
  • Tolerates freezing temperatures as low as -30 degrees Fahrenheit
  • Adds organic matter and green nutrients to the soil when turned under

Preferred soil conditions:

  • Well-draining, loose soil is ideal but tolerates clay and sandy soil as well
  • Tolerant of soil pH levels between 4.5 and 8.0. This test kit provides readings on soil pH and various other nutrient levels.
  • Application of high-nitrogen fertilizer can help winter rye get established. This organic formula from Burpee might be a good choice.

When to plant: Early to mid-fall.

When to turn under: Early spring, at least 2 weeks before you plan to plant spring crops.

Learn more about winter rye cover crops: University of Vermont

2. Oats

A photo showing oats growing in a field.

Family: Grain

Benefits:

  • Rapidly produces dense growth pattern, chokes out weeds, and protects against soil erosion
  • Germinates in temperatures as low as 38 degrees Fahrenheit
  • Breaks up/prevents soil compaction

Preferred soil conditions:

  • Good drainage
  • Moderately to slightly acidic soil conditions, preferably 4.5 to 6.0

When to plant: Early to mid-fall. Plant at least 6 weeks and up to 10 weeks before your first local expected frost

When to turn under: Early spring

Learn more about oat cover crops: Michigan State University

3. Hairy Vetch

A photo showing a hairy vetch plant with purple flowers.

Family: Legume

Benefits:

  • Naturally adds nitrogen to the soil
  • Grows quickly and forms a dense cover
  • Reduces weed establishment

Preferred soil conditions:

  • Well-draining soil that’s relatively high in phosphorous, sulfur and potassium
  • Prefers pH between 6.0 and 7.0

When to plant: At least 4 weeks before your first expected frost date. (Can also be planted in early spring for a summer cover crop, but is most effective as a winter cover crop)

When to turn under: Mid to late spring. Hairy vetch produces much of its nitrogen in the springtime, so it’s most ideal for the beds you want to use for summer crops (tomatoes, peppers, etc.) that require late-spring planting.

Learn more about hairy vetch cover crops: Penn State University

4. Fava Beans

A photo showing a fava bean plant.

Family: Legume

Benefits:

  • Greatly improves soil nitrogen levels
  • The strong root system breaks up compacted soil
  • Reduces populations of certain nematodes
  • Certain varieties may also produce an edible crop

Preferred soil conditions:

  • Will grow in clay or sandy conditions but prefers well-draining soil
  • pH levels 6.0 to 6.5 but tolerates pH slightly out of these parameters

When to plant: Late summer/early fall

When to turn under: Early to mid-spring

Learn more about fava bean cover crops: Research study published in Agronomy Journal

5. Clover

A photo showing a bed of clover plants.

Family: Legume

Benefits:

  • Thrives in many growing zones
  • Fixes soil nitrogen deficiencies
  • Produces dense, weed-blocking foliage
  • If allowed to bloom in the spring, flowers provide excellent food for pollinators

Preferred soil conditions:

  • Tolerant of poor soil conditions but thrives in well-drained soil
  • Slightly acidic soil, pH level between 6.0 and 7.2 is ideal

When to plant: 6 to 8 weeks before your local first expected frost date

When to turn under: Early to mid-spring

Learn more about clover cover crops: Penn State University

Tips for Planting and Turning Under Winter Cover Crops

  • Plant your winter cover crop as soon as you finish harvesting the last of your summer/fall vegetables
  • After spreading your seed, tamp it down and keep the soil moist until seedlings emerge.
  • Cut down your cover crop about 3 weeks before beginning your vegetable and flower gardening. A string trimmer is a great tool to use for cutting down cover crops in raised beds.
  • Allow the cut-down stems and foliage to dry out a few days before turning them into the soil. Since you’re working with a raised bed, a pitchfork is the ideal tool for this task.
  • After turning under, wait about another 2 weeks before planting your regular garden crops. This gives the cover crop’s root system, stems and foliage time to decompose a bit, further enriching the soil and improving soil texture.
  • Especially if you planted a dense cover crop like winter rye or clover, you can also put some of the cut foliage right into the compost.

RELATED: A compost tumbler is a great way to take advantage of home composting even if you don’t have much space to work with. Visit our post on the Yimby tumbler composter to learn how to use one!

Best Summer Cover Crops for Raised Beds

If you live in a hot, dry climate (like Arizona or New Mexico, for example), you know that the harsh weeks in mid-summer make it difficult (or impossible) for many vegetables to grow, much less produce a good crop.

In areas like these, planting your veggies in the fall, winter and early spring yields the best results.

But you don’t want to leave your soil bare during the harsh summer season. Weeds never miss a chance to get established, and the baking sun and lack of moisture can turn your soil into a hard clump. So here’s where summer cover crops come to your rescue.

Summer cover crops are usually less effective at long-term soil improvement, like reducing soil clods or adding high amounts of nutrients. They can do these things, but not to the degree that winter cover crops can.

Instead, the main goal of summer cover crops is to prevent your soil from drying out, eroding or getting taken over by weeds during the summer weeks/months. Since the growing season is shorter, fast-growing plants make the best summer cover crops for raised beds.

Our favorite choices are:

  • Buckwheat
  • Sorghum-Sudangrass
  • Pearl Millet
  • Cowpeas

1. Buckwheat

A photo showing buckwheat plants.

Family: Broadleaf

Benefits:

  • Fast to get established
  • Dense growth provides outstanding weed suppression and erosion prevention
  • Very low-maintenance
  • Increases soil phosphorus when turned under
  • Produces flowers that pollinators love

Preferred soil conditions:

  • Well-draining soil
  • Prefers full sun
  • Tolerant of low soil nutrients

When to plant: Spring or early summer

When to turn under: About 3 weeks before planting your late-summer or fall garden crops. Make sure to cut your buckwheat before the flowers go to seed or you may have unwanted volunteers.

Learn more about buckwheat cover crops: Oregon State University

2. Sorghum-Sudangrass

Sudangrass growing in a sunny field.

Family: Broadleaf

Benefits:

  • Quickly produces abundant growth
  • Excellent at weed suppression
  • Highly drought-resistant
  • Grows well in hot temperatures

Preferred soil conditions:

  • Tolerant of most soil pH levels but prefers 6.0 to 7.0
  • Can grow in a variety of soil textures
  • Does best with an application of nitrogen at seeding

When to plant: After last expected local frost date up to mid-summer

When to turn under: About 3 weeks before planting your late-summer and fall garden crops. Also, cut sorghum-Sudangrass down with a string trimmer a few times during the growing season to prevent overgrowth and seed formation.

Learn more about sorghum-Sudangrass cover crops: University of Vermont Extension

3. Pearl Millet

A photo showing pearl millet plants growing in a field.

Family: Grain

Benefits:

  • Great for mixing with buckwheat or sorghum-Sudangrass
  • Highly tolerant of heat and drought
  • Grows very quickly
  • Can grow in many different soil types/conditions

Preferred soil conditions:

  • Will grow in heavy clay or loose sandy soil but does best in well-draining, rich soil
  • Tolerant of a wide range of soil pH levels but prefers pH between 5.5 to 6.5

When to plant: After last expected local frost date

When to turn under: About 3 weeks before planting late-summer or fall garden crops

Learn more about pearl millet cover crops: University of Missouri Extension

4. Cowpeas

A photo showing cow pea plants.

Family: Legume

Benefits:

  • Adds high amounts of nitrogen to the soil
  • Attractive to helpful garden insects
  • Tolerant of drought after getting established
  • Forms deep taproots that break up soil clumps and compactions

Preferred soil conditions:

  • Well-draining soil in a sunny location
  • Grows well in a variety of soil pH levels but does best in slightly acidic conditions
  • Tolerates a range of soil types/conditions

When to plant: After last expected local frost date, and up until 9 weeks before first expected fall frost

When to turn under: About 3 weeks before planting late summer/fall garden crops.

Learn more about cowpea cover crops: Midwest Cover Crops Council

Tips for Planting and Turning Under Summer Crops

  • Plant your summer cover crops as soon as you finish harvesting your spring vegetables.
  • Even if you’re not in a harshly hot climate, you could still find yourself with random empty spaces in the garden for a few weeks at a time. If you do, you can plant a cover crop around your vegetable or flowering plants. Just make sure you’re still giving your vegetable plants enough room to establish their own root systems. Buckwheat is a great choice here, thanks to its fast growth pattern.
  • If your cover crop produces flowers (and therefore, seeds), plan to cut when about half of the plants have blossoms and at least 3 weeks before you plan to plant your fall crops. Toss the cut portions into the compost and turn under the remaining plant matter and root systems.

Where to Find High-Quality Cover Crop Seeds

One great thing about cover crops for raised beds is that you’re working on a smaller scale, and you won’t need to invest a lot of time or money in your cover crop.

The general rule of thumb is about 2 to 3 pounds of cover crop seed per 1,000 square feet.

Obviously, raised beds vary greatly in size, but they’re almost always (much) less than 1,000 sq. ft. For example, a bed that’s 4 feet by 8 feet has a total square footage of 32 feet.

So unless you’ve got dozens of raised beds to care for, one pound of seed should be more than sufficient. In fact, for most home gardeners, a few packets of cover crop seed should be just fine.

There are many options for buying quality cover crop seeds out there, both in standard-size packets or in bulk.

Botanical Interests is a favorite source of mine for garden seeds of all kinds, and you’ll find a nice selection of cover crops here:

Amazon also has some seeds for sale, including this winter rye from Thunder Acres. There’s also this 13-seed cover crop seed mix that contains clovers, cowpeas, buckwheat, vetch, millet and a few others as well.

If you’re interested in planting sorghum-Sudangrass, you can find it at the Silver Stone Yard shop on Etsy.

Final Thoughts

As you can see, cover crops for raised beds are a fantastic idea for maintaining the health of your garden soil and the prospects for your garden production in the future.

So perhaps it’s time to start experimenting and reaping the rewards of a simple and hugely beneficial cover crop practice.

We want to hear from you! Do you have any other questions about cover crops for raised beds? Or maybe some helpful tips to share? Let us know in the comments!

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About Erinn Witz

Hi! I’m Erinn, a Midwestern gal who’s just as interested in honing my gardening skills as you are. I’m here to show you that if I can do this growing thing, seriously, YOU can too! 

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