Grow Cover Crops and Green Manure in the Summer

By on April 29, 2013

Here's how your summer cover crop could look at the end of the season -- some has been cut down to give fall kale a happy home.

Most cover crops are planted in late summer, but there are some cover crop seed mixes that can go in the ground in the springtime and give you benefits by the end of the summer.

Cover cropping is a cheap and effective way to fertilize your garden, hold topsoil in place, and retain moisture during the summer heat.

Planting a cover crop on a fallow garden bed or farm field is a classic organic gardening technique. It also seems rather mysterious to those new to organic gardening. But it’s simple as can be.

The principle of cover cropping is to grow plants that will nourish the soil. If you cut down cover crops that have high nitrogen levels, and turn them into the soil (where they will break down) the cover cropping is called “green manure”. In our video about green manure Tricia shows you how to till in, turn in, or compost a cover crop. You’ll be adding more organic matter, which will improve soil structure over time, when you till in these green crops.

We have the largest selection of cover crops, at the best prices, on the West Coast.

buckwheat summer cover crop

Planting in the spring for a summer cover crop

For a fast, warm-season cover crop that shades out weeds, buckwheat (shown above) would be a good choice. It germinates when the soil is 45-105°F and it is ready to till in in about a month.

An all-around summer/warm weather cover crop is our Summer Soil Builder Mix.  It needs a Cowpea Inoculant.

We have a complete list of summer cover crops. Go to our Warm Weather Cover Crop page for the complete list of seeds that grow in the warmth of the summer.

nitrogen fixing nodes

Choosing a cover crop for any season

Most home gardeners want to replenish nitrogen in the soil, since vegetables use lots of nitrogen when they grow and fruit.  Have you heard of “nitrogen fixing”? That means the new nitrogen produced by the cover crops stays in the soil. You can see the nitrogen-fixing nodes on the roots in this photo.

Legumes are good for adding nitrogen to soil, so many cover crop seed mixes are high in legumes. Legumes fix more nitrogen if you treat them with an inoculant before you plant them. The inoculant contains the naturally occurring soil rhizobacteria that are essential to nodule creation and the transfer of nitrogen back into the soil.

Choose a cover crop that will grow well in your climate and the upcoming season. It’s easy to find that information on our Cover Crop page. Click the link for Cover Crop Solution Guide, which sorts the seed mixes by when to plant them and what they do.

Cover crops are not just for fixing nitrogen—for instance, they can be effective clod-busters (watch a video clip to see what Bay Area organic farmer Fred Hempel of Baia Nicchia Farm says about that. Think about which soil problems you want to solve and then check our Solution Guide for Cover Crops to find out which seeds will do the trick for you.

summer soil builder mix cover crop

How to plant a cover crop

1)  Harvest your vegetables, then pull out the plants and other debris.

2)  Calculate the square footage of the area you want to plant with cover crop.

3)  Buy enough seed for the area (our Summer Soil Builder Mix is shown above).

4)  Inoculate the seeds, if necessary, and plant them.

5)  Water regularly if your cover crop needs summer irrigation.

Whether you plant in spring or late summer, the rule of thumb is to cut or turn in your crops when half of a cover crop stalk is in bloom.

Get your Advanced Organic Gardener merit badge when you grow a cover crop—whether you plant in spring or late summer.

  Comments (6)


So if I use a legume as a cover crop then I can’t plant another legume in the same bed for an edible crop? Example, I use Fava beans as a cover crop but then I can’t plant peas or beans in the same place for a year to have a good rotation of crops. But in my small garden that’s hard to do. I grow a lot of brassicas also. Should I be using wheat as a cover crop or something else?


Posted by Carla Edwards on Nov. 14, 2014 at 5:42:32 PM

Legumes are not typically prone to soil born diseases. I do not think that you need to be that concerned with following a legume cover crop with a legume like peas or beans.

Posted by Suzanne at Peaceful Valley on Dec. 01, 2014 at 3:41:55 PM


I am having surgery this June and can’t garden most of June and July. What cover crop can I plant in my 8 raised garden beds that don’t need cutting and will keep weeds from growing in my beds during this time? I live on the coast in northern Maine. I will try planting tomato plants (hope it’s not too cold) and red clover in one bed, but the others will be fallow. Help!

Posted by Claire Daniel on Mar. 01, 2015 at 9:09:30 AM

The Summer Soil Builder Mix is great for summer planting and growth. It is a mix of buckwheat and cowpeas. You would want to cut it down though before the buckwheat sets seeds. The mix will need to be inoculated because of the cowpeas, they fix nitrogen with the help of the rhizobia bacteria.

Posted by Suzanne at Peaceful Valley on Mar. 04, 2015 at 11:48:55 AM


I heard somewhere long ago that a good plant to cultivate in a fallow garden was “Lupine”,
that it is a natural nitrogen builder and is easy on the eyes (has nice blooms).
Is there anything else in the same category? With flowers?
I was planning a mass planting on a medium size plot.

Posted by Ed Wellman on Mar. 29, 2015 at 3:13:41 PM

Many clovers produce nice flowers and fix nitrogen, crimson clover comes to mind. Sweet peas are legumes and should fix nitrogen as long as there is sufficient rhizobia bacteria in the soil (can also inoculate with it). Many of the vetches have pretty purple flowers as it can fix nitrogen.

Posted by Suzanne at Peaceful Valley on Mar. 31, 2015 at 2:59:31 PM

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