Not many home gardeners think about cover crops. Many, in fact, are unaware of them altogether. Those who have heard of them may think that they are just for commercial farmers. But the truth is, cover crops can be very beneficial to the backyard gardener.
Why Use Cover Crops?
For the home gardener, cover crops offer a wide variety of advantages for the garden. Often called “cool season cover” these crops are annual plants that are grown to add organic matter and nutrients to the soil and protect it from wind and water erosion in the fall, winter and spring.
Most cool season cover crops will grow throughout the winter, though very slowly, and then accelerate their growth in the spring when the weather warms and days get longer. At this point, most gardeners will till the crop into the soil as a “green manure” before the crop goes to seed. In three or four weeks, the cover crop has composted and begun releasing its nutrients into the soil.
The cover crop chosen depends on your space, time and effort, and need.
Which Cover Crops for Gardens
Probably the most common are legumes such as alfalfa, peas, beans and clovers. These are a favorite because they have the ability to draw nitrogen from the air. When they are tilled into the soil, the nitrogen is released and is available for the next crop you plant there to use. The process is called nitrogen fixation and is accomplished at the root by a beneficial bacteria called Rhizobium.
Grasses are another common and popular choice for garden cover crops. These add organic matter to the soil and are easily removed (and composted) or tilled in, as their turf (roots) are relatively shallow.
Seed mixtures are also available with both grasses and legumes. Mixtures of various types of each are available at most garden stores, grain sellers, and seed outlets. These are often tuned for specific climate, season, type of garden, etc. The legumes are often sold with the proper inoculate to encourage Rhizobium proliferation.
Before choosing a seed mixture or monoculture, however, the gardener should consider several factors:
- What is the appropriate climate for the cover crop?
- Does the crop have a benefit your garden can use?
- How persistent is the crop you’re planting – will it easily be tilled in and killed, or will it become a nuisance?
- What is the expected seed maturity time frame for the cover crop and does that fit your planting schedule?
- Is the crop designed for fall or spring planting?
Knowing the answers to those questions will help you make the best choice for your garden’s needs.
How and When to Plant Cover Crops
Most cover crops are planted through seed broadcasting. After clearing the soil of all unwanted weeds and leftover crop plants, the gardener can rake the topsoil to create shallow furrows and then broadcast the seed over the area. Raking in the opposite direction (cross-wise) will fill in the furrows, burying the seeds at roughly 1/8 to 1/4 inch. Then water as directed.
Most cover crops are pernicious and, once established, will drive out most weeds that may be around in the fall. Weeding is usually not required at all, in fact. The cover also tends to stay relatively green throughout the winter, which adds to the aesthetic appeal of the garden. Just be sure to pull it up or till it in before it goes to seed — or else you’ll have unwelcome weeds for the rest of the summer!