Which Cover Crops for Gardens Work Best in Your Climate?

What is Green Manure and How Does it Benefit Your Garden?

Which Cover Crops for Gardens Work Best in Your Climate?

Reading Time: 5 minutes

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.

Legumes

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.

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.

Legumes
Spring and Summer Seeding
Climate Best Used InInformation
AlfalfaAllDeep root system, good as mulch
BeansAllCan be raised as crop, harvested and turned under or turned under when flowering as green manure
Alsike CloverNorthWorks well in areas with acidic soil and/or wet areas
Red CloverCentral and NorthCan be cut when green as mulch or allowed to seed as perennial crop
White CloverAllBest as green manure
Sweet CloversAllDeep taproot system; better in dryer conditions than other clovers
CowpeasCentral and SouthDrought resistant; fast growing; does well in hot climates
Hairy IndigoDeep SouthDoes well in hot, humid climates; resistant to nematodes
LespedezaSouthHelp restore acidic overused soil
Late Spring/Fall Seeding  
Blue LupineGulf CoastRequires fertile soil
White LupineDeep SouthWinter hardy; requires fertile soil
Yellow LupineFloridaNot winter hardy; does well in acidic, less fertile soil
Purple VetchDeep South and Gulf CoastHigh producer of green material; not winter hardy
Common VetchSouthNot winter hardy; does not like sandy soil
Annual Sweet Yellow CloverSouthGood in winter, especially in the Southwest
Field PeasSouthGrown to harvest and turned under or turned under when in flower; used as a spring crop in the North
Hairy VetchAllMost winter hardy vetch

Non-Legumes

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.

Nonlegumes
Spring and Summer Seeding
Climate Best Used InInformation
Pearl MilletAllExcellent weed suppressor; fast growing
Bur CloverSouthIf allowed to go to seed every five years, it will be an annual fall crop
BuckwheatAllFast growing; excellent weed suppressor; can be grown to harvest and turned under or turned under when in flower for green manure
Crimson CloverCentral and SouthExcellent winter annual
Fall Seeding  
WheatAllPrefers fertile soil; some varieties extremely cold hardy
RyeAllExcellent winter cover crop; most hardy small grain crop
Annual RyegrassAllRapid growth; excellent winter cover crop
Smooth BromegrassNorthWinter hardy; extensive fibrous root system
OatsAllDoes not like heavy clay; Must plant spring varieties in the North
BarleyAllMust plant spring varieties in the North
KaleAllExcellent 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

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