Peony 'Sarah Bernhardt'

Peony 'Sarah Bernhardt'

Thursday, September 24, 2015

Time for Planting Cover Crops

Happy Autumn Equinox my gardening friends!

Autumn is officially here. In Portland we had two nights of overnight lows in the 40s. This morning it was back up to 55 degrees. I absolutely love autumn weather. The garden is changing with the season. Leaves are turning color, fall cyclamen & colchicum are peaking up their bright low-growing blooms, and the summer vegetable garden is winding down.

For about the next month tomatoes will continue to ripen if the temperatures stay mild. Zucchini, summer squash, cucumbers, basil and beans should continue producing. Pumpkins and winter squash will ripen on the vine. If you planted a crop for fall & winter harvest it should be growing steadily. My spinach is ready to harvest, while the kale, broccoli, and kohlrabi are still immature and growing.

As we begin thinking about putting our hardworking vegetable garden to rest for the winter, be it in-ground, raised beds, or containers, please consider planting cover crops. In Portland, September and October are the perfect time for planting cover crops.

Cover crops are sometimes known as "green manure." Cover crops are quick growing and planted primarily to keep the soil covered for a short period of time, often during the fall and winter. Then they are turned under as "green manure" where they decompose and add organic matter to the soil. In addition to adding organic matter to the vegetable garden, cover crops suppress weeds by providing competition, reduce erosion, and add nutrients.

Common cover crops are crimson clover, dutch white clover, vetch, rye, buckwheat, fava bean, oilseed radish, and austrian peas. There are also cover crop seed mixes that contain a variety of cover crops.

The lush green growth of cover crops returns large amounts of organic matter to the soil. Organic matter stabilizes moisture content and improves garden soil texture. When dug under all the nutrients stored in cover crop plants are returned to the soil.

Crimson clover, dutch white clover, fava beans, austrian peas and vetch are all members of the legume family. This means when they are used as a cover crop they actually return nitrogen to the soil. Legume plants are hosts to nitrogen-fixing bacteria and extract nitrogen from the air and convert it into a form that can be used by plants. Legumes are awesome!

Autumn is a great time to plant cover crops. Unless you are growing winter crops, you are probably cleaning up and putting your vegetable garden to bed at this time of year. Instead of just letting your garden rest during the winter why not plant some cover crops? Depending on the variety of cover crop you choose, they are usually seeded September-November. Plant cover crop seeds by broadcasting; check seeding rates for individual varieties. The seeds need to be covered by soil and kept evenly moist while germinating. Most cover crops need a full sun location.

Last year on October 6th we planted crimson clover in our 3 raised beds we put to rest for the winter. With a daily light watering we were rewarded with germination in under 7 days! Crimson clover has the nitrogen-fixing powers of a legume, it forms a dense green carpet during the winter, it is easy to turn under in the spring, and it develops beautiful bright flowers in the spring that attract bees. Crimson clover is by far my favorite cover crop. I plant it every autumn and highly recommend it.

Fava beans are another excellent cover crop that grow into tall 3 foot vigorous plants with beautiful flowers. In addition to their nitrogen-fixing powers, favas have a deep taproot that loosens up those hard clay soils in Portland.

Oilseed radish have the same beneficial taproot quality of fava beans, however, they are in the cabbage family so you need to consider them in your garden crop rotation schedule.

Rye germinates fast and tolerates harsh conditions. Their dense mat of roots makes them excellent erosion controllers. However, in my experience rye and other cereal grasses are very difficult to remove unless you use a rototiller. A few years ago in my small community garden it was virtually impossible for me to use a hoe to uproot the plants in time for spring planting.

You can pick up cover crop seeds at your local nursery or garden center. Plant them this fall and reap the rewards come next spring!

Happy Autumn, Jolie

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