By Gail Cocker, Master Gardener, SCMG
If you love growing vegetables and you want to protect and improve your soil, then incorporating cover crops into your garden growing plan is a great idea.
Trifolium incarnatum (Crimson Clover)
Cover crops are good for gardens because they replenish the organic matter lost during annual cultivation. Adding biomass to the soil results in a better soil structure that is well aerated and has a good water infiltration rate. Some cover crops are in the legume family and have the added benefit of fixing nitrogen for your crops. Tall and dense cover crops are great for weed suppression and many produce flowers that attract pollinating insects and beneficials. Once cut down before they set seeds, you have a layer of mulch between your rows. Planting a cover crop in the fall also helps prevent soil erosion over the winter.
A cover crop is a general term for any crop grown to prevent erosion, to improve soil structure and to improve soil fertility. It is not necessarily incorporated into the soil while the term “green manure” is a soil improvement practice of incorporating any crop into the soil while still green. Cover crops can be living mulch when interplanted with an existing crop. I often plant crimson clover in between my rows of corn for example.
It used to be that only commercial farms or market gardens practiced cover cropping as they had the heavy equipment required to till the dense, fibrous root mass into the soil. Now, however, there are many cover crops appropriate for the home gardener who has a string trimmer and a broadfork.
You can sow cover crop seeds in the bare section of your garden after you have harvested early crops. Or sow between rows of vegetables to keep weeds down. If you are creating a new garden plot, then the deep rooted, oilseed radish cover crop is a good choice as the long taproot will break up the soil for you. (Note that this plant is in the Cruciferae family, so you will want to avoid cabbage, cauliflower, broccoli, brussel sprouts in that patch immediately following.)
A couple of cautions concerning cover cropping however. Cover crops must be turned under in spring at least 3 weeks before planting to avoid the decomposition competing with your veg. crops. Depending on weather, this may delay your usual planting dates. As well, if you allow crops to go to seed, (ie annual rye grass), it will become “weeds”. Some of the perennial cover crops are difficult to remove once established (ie white clover). My advice if you are new to cover crops, stick to the annuals. Sow in the fall and they will die over the winter and can be easily turned into the soil in the spring.
There are a multitude of choices for cover crops so you need to think about your primary goals; erosion protection? nitrogen production? weed suppression? attracting beneficials? soil cover for winter? Once you have that narrowed down, check out the seeds and their attributes on the OMAFRA site. They also have a list of seed suppliers you may want to check out as it is unlikely you will find these seeds in the carousel at your local nursery.
Fagopyrum esculentum (Buckwheat)