Idaho Falls Community Garden Association

Cover Cropping - Summer and Winter

Why should I plant a summer cover crop?

You can get a head start on improving the quality of your garden soil for next year's season with some simple steps taken in the summer to boost the amount of organic matter in your soil with summer cover crops.  A summer cover crop will add significant amounts of organic matter to your soil, yielding a variety of long term benefits. Increased organic matter improves the water holding capacity of the soil, improves drainage in clay soils and provides a range of macro and micro nutrients that optimize plant health. In a recent study done by a university ag department in the mid-west plants that were grown in soils that were amended with a full range of nutrients PLUS compost did significantly better than those grown in the amended soil alone. There are two ways to add organic matter; grow it or pile it on. Growing your cover crop right on the soil you wish to amend saves money and time - no expensive compost to haul and shovel, just some seeds to scatter and water when you take care of the rest of your garden.  A crop of hairy vetch and rye will add nitrogen equivalent to 13 pounds of 10-10-10 fertilizer and 57 lbs. of biomass to a 400 ft2 garden.

What are the best seeds to use?

There are several choices for cover summer cover crops in our area. Legumes of any kind make a great cover crop (peas, beans, soybeans, fenugreek etc.) because they add significant amounts of organic matter and  help fix nitrogen in the soil by extracting it from the air and passing it into the soil through nodules on its roots.  Another good choice is buckwheat. Extremely vigorous, it is known for its ability to suppress other plants growth. Buckwheat was able to keep both field bindweed and quack grass in check in a trial plot at Eastside a few summers ago. It matures quickly and can be tilled or dug in in as little as 4-5 weeks. (Remember that even if the cover crop doesn’t reach maximum maturity in the time it has in your plot whatever green matter is there when you turn it into the soil is making a difference.) It also has a very pretty white blossom but be sure to cut it before it goes to seed. Another fast grower is annual rye grass which will yield enormous amounts of organic matter after only several weeks of growth.

How do I do it?

If you can sow seeds you can grow a cover crop. Any time you have an area which will be unused for more than a few weeks a cover crop can go in. Broadcast the seeds over the area, rake them in - more vigorously for large seeds like peas- and then water as you do the rest of your garden. If there is sufficient time for the crop to get several inches high turning it under is easier if you mow it first. The mowing also chops the plants into smaller pieces which will break down more quickly in the soil. The plants should be turned in when they are in about 75% flower or, for buckwheat, when frost is near, whichever is sooner.  A succession of cover crops can be sown, one right after the other, if there is sufficient time in the season. For more details you can go to Cover Crop: Preparation and Planning.

What about winter cover crops?

The answer in a word - yes! While our cold winters limit the variety of cover crops that we can successfully grow there are a couple that will do the job. The Peaceful Valley catalog has a Cold Zone Soil Builder mix that should also do well in our area.

Where can I get the seeds?

Some local garden centers carry annual rye; ask them to carry some of the other seeds. Peaceful Valley Farm Supply (888 784-1722), in northern California, is a great source of many different types of cover crop seeds. If there is sufficient interest among the gardeners the IFCGA can also order bulk quantities of the hard-to-find seeds like buckwheat and soybeans. If you are interested talk to your garden coordinator or e-mail us at Remember that  building your soil through the addition of organic matter is one of the best things you can do for your garden!

For more information about the Idaho Falls Community Garden Association call (208)524-0383 or