When it comes to cover crops for gardens, the list of benefits is extensive. Choosing the best cover crop to accomplish the job in your climate is where most people run into difficulty. There are two main groups of cover crops for gardens, legumes and non-legumes and each group has plants which grow better in certain climates.
Both groups can be used to create green manure. What is green manure? Green manure is a way of fertilizing the soil by allowing cover crops to remain where they are sown as they decompose. They can be left on top of the soil to serve as mulch and slowly fertilize the soil. If you want them to serve as a faster soil amendment, you can plow or till them under when they are still green and before they go to seed.
When you say legume, the first crop most people think of is peas and beans. Yep, they are legumes, but they are a small part of this vast group of plants. Legumes are excellent nitrogen fixers for the soil making them beneficial cover crops for gardens. They are used to prevent erosion, prevent weeds and add organic matter.
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This group includes winter annuals such as hairy vetch, Austrian winter peas, crimson clover, and more. As perennials, there are clovers of all kinds like white and red. There are also a couple of biennials like sweet clover and a large group of summer annuals. In cooler climate areas like here in the panhandle of Idaho, cover crops for gardens which are considered winter annuals are grown in the summer.
So you see your climate not only determines what your plant but when you plant it.
Annual winter legumes, like the name implies, are planted in early fall for maturing over winter to provide nitrogen and biomass in time for spring planting. Both perennial and biennial legumes grow quickly making them perfect forage crops between main crops. As forage crops, they can be turned under for the soil or harvested to feed livestock and poultry. The use of summer annual legumes as cover crops for gardens depends totally on your climate. In colder climates, like mine, many of these aren’t good options.
Spring and Summer Seeding
|Climate Best Used In||Information|
|Alfalfa||All||Deep root system, good as mulch|
|Beans||All||Can be raised as crop, harvested and turned under or turned under when flowering as green manure|
|Alsike Clover||North||Works well in areas with acidic soil and/or wet areas|
|Red Clover||Central and North||Can be cut when green as mulch or allowed to seed as perennial crop|
|White Clover||All||Best as green manure|
|Sweet Clovers||All||Deep taproot system; better in dryer conditions than other clovers|
|Cowpeas||Central and South||Drought resistant; fast growing; does well in hot climates|
|Hairy Indigo||Deep South||Does well in hot, humid climates; resistant to nematodes|
|Lespedeza||South||Help restore acidic overused soil|
|Late Spring/Fall Seeding|
|Blue Lupine||Gulf Coast||Requires fertile soil|
|White Lupine||Deep South||Winter hardy; requires fertile soil|
|Yellow Lupine||Florida||Not winter hardy; does well in acidic, less fertile soil|
|Purple Vetch||Deep South and Gulf Coast||High producer of green material; not winter hardy|
|Common Vetch||South||Not winter hardy; does not like sandy soil|
|Annual Sweet Yellow Clover||South||Good in winter, especially in the Southwest|
|Field Peas||South||Grown to harvest and turned under or turned under when in flower; used as a spring crop in the North|
|Hairy Vetch||All||Most winter hardy vetch|
With non-legumes, the first crop thought of is rye grass but like legumes, the class of non-legume cover crops for gardens is large. Your climate determines which of the annual or perennial cover crops you can use just as it does every other plant or cover crop you choose.
Unlike legumes which fix nitrogen, non-legume cover crops use nitrogen. They’re just as efficient at preventing erosion, suppressing weeds, and adding organic matter to the soil. Many people plant a mix of legumes and non-legumes. We do.
Cereal grains used as cover crops have the widest range of climate in which they can thrive. The winter annual cereal grains, like wheat, are usually planted in late summer to early fall to allow them time to establish themselves before they go dormant in the winter. With the spring green up, they flourish and increase their biomass contribution as they mature their grains.
Buckwheat is our top choice for a perennial cover crop for gardens. It’s not a grass, but many people use it to accomplish some of the same goals as they would a summer annual grass. It makes good forage and provides needed food for the bees and other insects as it’s one of the plants that bees love. It also accomplishes all the benefits of other cover crops.
As with many perennial cover crops for gardens, you can prepare new areas for garden planting by sowing one or more of these early, letting them go to seed and decompose where they lay. Next spring the new crop will come up and before it seeds, turn it under for green manure. The soil is rich and ready without weeds as the cover crop has choked them out.
We were happy to find out the organic buckwheat seed we brought with us from Louisiana will work here in the panhandle of Idaho. The season is shorter, but the same goals can be accomplished.
Spring and Summer Seeding
|Climate Best Used In||Information|
|Pearl Millet||All||Excellent weed suppressor; fast growing|
|Bur Clover||South||If allowed to go to seed every five years, it will be an annual fall crop|
|Buckwheat||All||Fast growing; excellent weed suppressor; can be grown to harvest and turned under or turned under when in flower for green manure|
|Crimson Clover||Central and South||Excellent winter annual|
|Wheat||All||Prefers fertile soil; some varieties extremely cold hardy|
|Rye||All||Excellent winter cover crop; most hardy small grain crop|
|Annual Ryegrass||All||Rapid growth; excellent winter cover crop|
|Smooth Bromegrass||North||Winter hardy; extensive fibrous root system|
|Oats||All||Does not like heavy clay; Must plant spring varieties in the North|
|Barley||All||Must plant spring varieties in the North|
|Kale||All||Excellent cover crop for winter; can be harvested all season|
Because non-legume cover crops for gardens are higher in carbon than legume crops, they take longer to break down. My simple understanding of this process is that fewer nutrients are readily available to the next crop because the carbon to nitrogen ratio is high and takes longer to breakdown.
So why do people plant non-legumes as cover crops for gardens? Because when the process is complete, the organic matter left is much greater than that of the legumes. This means a richer, more fertile soil in the end. They also keep nitrogen from leaching out of the soil through erosion or weeds feeding off it.
One way to deal with this, if you want to use the spot right after a non-legume cover crop, is to plant a crop which is not a high nitrogen feeder. It will have what it needs there. Mixing non-legume and legume cover crops for gardens is the most efficient way to balance the delicate world of your soil.
I prefer letting the area rest allowing the billions of little microbes and other critters living under the soil to do their job before I plant in an area where non-legume cover crops for gardens has been used. If you can allow this time, you could plant a nitrogen fixator crop behind the non-legume and give the area an extra boost.
Do you use legumes, non-legumes or a combination of the two as cover crops for gardens?
Safe and Happy Journey,
Rhonda and The Pack