Farmers around the world grow cover crops to increase crop yields. Cover crops, also known as green manures, are an excellent tool for vegetable gardeners, especially where manures and compost are unavailable. They lessen soil erosion during the winter, add organic material when turned under in the spring, improve soil quality, and add valuable nutrients.
Protect and improve your soil
- Popular fall-planted cover crops include oats, winter rye, winter wheat, crimson clover, and hairy vetch. The latter two crops are legumes- plants that can add a lot of nitrogen to your soil after they decompose.
- These crops are typically planted as early as August 15, but no later than October 10th. They should make some growth before the first hard frost.
- Some cover crops (oats and daikon radish) are killed by cold winter temperatures, but most go dormant and resume growth in the spring.
- Cover crop roots grow deeply into the soil pulling up nutrients that might otherwise leach out of the soil.
- The crops are turned into the soil before going to seed, usually sometime in late April or early May.
- Other cover crops, like buckwheat and Dutch white clover, are sown in the spring or summer to cover and improve bare soil.
Steps for planting a fall cover crop
- Be a good steward of the earth by planting a cover crop this fall.
- Decide which cover crops to plant. Combine legumes and non-legumes when possible. If you plant a two-species mixture, use about 60% of the recommended amount for each.
- Sow oats if this is your first time trying a cover crop or if you want to be able to plant early spring vegetables. Oats are killed by the first hard freeze, leaving a brown decomposing mat in spring.
- Purchase seed locally if possible from a farm supply store or garden center. You can also order cover crop seeds from most retail seed companies.
- To sow a cover crop over an entire bed: Prepare the soil by removing vegetable plants, weeds, and mulch from the summer. Loosen the soil with a garden fork and rake the area smooth.
- To sow a cover crop while vegetable crops are still producing: Remove mulch from around plants and rake the area smooth. Your cover crop will get a good start but will not interfere with vegetable plant growth.
- Now let’s plant: The seed must directly contact soil to germinate. Use the amount of seed shown in the chart. Broadcast the seed by hand or with a hand-held broadcast seeder, preferably before a rain, and gently rake seeds evenly into the soil. Then walk on the seeds to press them into the soil. Mixing seeds with soil or compost will make it easier to distribute the cover crop seeds evenly by hand.
- Winter wheat and winter rye will produce massive root systems- great for breaking up tight, clay soil.
- Spring planting may be delayed somewhat by a cover crop (except for oats and daikon radish) since you must allow about 2 weeks for the plants to break down.
| Type (L = legume) | Amt. (oz.) to Sow per 100 sq. ft. |
When to Sow** | When to Turn Under |
Notes |
|---|---|---|---|---|
| Barley | 3 - 4 | spring or late summer/ fall |
spring | Not as hardy as rye. Tolerates drought |
| Buckwheat | 3 - 4 | spring or summer | anytime | Grows quickly. Will reseed itself. Not hardy. |
| Crimson clover***(L) | 1 - 2 | spring or late summer/ fall |
fall or spring | Beautiful spring blooms. |
|
Forage radish* (a type of daikon radish) |
1 - 2 | late summer/fall | spring | Large white roots break up clay soil. All parts are edible. Monitor for harlequin bug. |
| Spring oats* | 3 - 4 | spring or late summer/fall | summer spring |
Not cold hardy, tolerates low pH. |
| Winter rye | 3 - 4 | late summer/fall | spring | Very hardy. Produces a massive root system. Cover crop that can be planted the latest in the fall. |
| Hairy vetch (L) | 3 - 4 | late summer/fall | spring | Slow to establish. Very hardy. Till under at bloom, can become a weed. |
| Winter wheat | 3 - 4 | late summer/fall | spring | Easier to manage and terminate in spring than rye or barley. |
*Will winter-kill in most years, leaving a “mat” of dead vegetation which can be planted through in spring or turned under.
**Sow late summer/fall crops from August 15- October 1, depending on location, species, and weather forecast.
*** Legumes, like crimson clover and hairy vetch, together with special soil bacteria, transform nitrogen from the air into a plant-available form. You can aid this natural process by purchasing an inoculant with your seed - Rhizobia spp. bacteria. You coat the cover crop seeds with the inoculant by mixing them together in a bag.