How To Choose the Right Garden Cover Crop For You

Many choices abound to match your climate, soil type and the season of the year.

By Jan Wiese-Fales | Photos By UGA Extension - University of Georgia

Cover crops, if planted and managed correctly, will improve the quality of your soil and enhance your gardening efforts. Those profiled below are the most widely adaptable and most frequently utilized, though it is not a comprehensive list. You must take your climate and soil into consideration, as well as what you hope to accomplish.

NON-LEGUMES

It is important to note that grassy non-legumes tie up nitrogen for immediate use, which is somewhat mediated by planting them with a legume crop or planting a legume afterwards. Mixtures of both can be very effective.

Barley

  • Cool-season annual cereal grain, can be grown farther north because of short growing period, hardy to USDA Zone 7
  • Inhibits weeds, provides biomass, scavenges nutrients, controls erosion, improves soil structure, suppresses some insect pests
  • Spring-planted before late season vegetable plantings, fall-planted with legumes

Brassicas and Mustards: Mustard, Rapeseed, Tillage Radishes

  • Fast-maturing annuals, hardy to 25 degrees F; some varieties of rapeseed hardy to 10 degrees F
  • Inhibit weeds, nematodes and soil borne diseases, excellent nutrient scavenger, deep taproots loosen soil, great biomass
  • Spring planted for re-cropping in fall but should not be in a rotation with other brassicas; fall planted for winterkill

Buckwheat

  • Summer or cool season annual that matures in 70 days
  • Inhibits weeds, attracts beneficial insects and pollinators, roots condition the soil and scavenge phosphorus for the next crop
  • Planted after early crops are harvested, cut for fall vegetable planting—residue decomposes quickly
  • Should be cut back shortly after it begins to flower and can be cut a couple of times over the season

Oats

  • Cool season annual cereal that grows quickly; hardy to USDA Zone 7
  • Inhibits weeds, scavenges nutrients, adds biomass, improves performance of legumes when planted together
  • Fall-planted, especially with legumes

Rye, Winter or Cereal

  • Cool-season annual cereal grain, most versatile cover crop, hardy to USDA Zone 3
  • Reduces soil-borne diseases and nematodes, inhibits weeds, excellent biomass, best nitrogen-scavenger, reduces winter erosion and retains soil moisture
  • Fall-planted, often with a winter annual legume, chopped off in spring

Sorghum/Sudangrass Hybrids

  • Summer annual grass, fast-growing for wide adaptation
  • Inhibits weeds and nematodes, loosens and aerates subsoil if mowed once to increase root mass, unrivaled for biomass
  • Planted in spring as a rotation to recondition soil for later plantings, or in fall for winterkill

LEGUMES

Crimson Clover

It is suggested that legumes be treated with an inoculant—Rhizobia bacteria—before being planted in order to insure maximum nitrogen fixation.

Crimson Clover

  • Winter or summer annual, rapid fall growth, hardy to USDA Zone 7
  • Good source of nitrogen, suppresses weeds, good green manure, beautiful flowers attract pollinators and beneficial insects
  • Spring-planted before other crops and over-seeded in established crops, good fall-planted with oats or rye for winterkill; seed re-growth problematic, so must be mowed after early bud stage

Cowpeas

  • Summer annual legume, heat-loving, tolerates drought and some shade
  • Inhibits weeds, good source of nitrogen, good green manure, attract beneficial insects and pollinators
  • Good summer planted before fall cropping or in a crop rotation, cut before seed pod formation, fall-planted with sorghum-sudangrass for winterkill.

Hairy Vetch

  • Winter or summer annual, drought-tolerant, adaptable into USDA Zones 3 and 4
  • Excellent source of nitrogen, scavenges phosphorus, suppresses weeds, reduces erosion
  • Can be planted early in spring and summer and chopped for mulch, good planted with oats and rye in fall and chopped in spring

Additional Resources

Several states and regions have online cover-crop decision tools, such as:

New York/Northeast: http://covercrops.cals.cornell.edu/decision-tool.php

Midwest: http://mccc.msu.edu/covercroptool/vegtool.php

The Sustainable Agriculture Research and Education program has published an excellent in-depth look at cover crops. It is available for download at www.sare.org/Learning-Center/Books/Managing-Cover-Crops-Profitably-3rd-Edition/Text-Version/Benefits-of-Cover-Crops

The Ontario Ministry of Agriculture, Food and Rural Affairs also offers extensive information on cover crops at http://www.omafra.gov.on.ca/english/crops/facts/cover_crops01/covercrops.htm

USDA list of cover crops: http://mccc.msu.edu/covercroptool/vegtool.php