A winter crop of rye yields both delicious grains and loamier soil for spring plantings.

Soil does not like to be bare. Nature continuously spreads seeds to ensure that all soil is covered by some type of plant. When we cultivate any crop, we are interfering with the natural cycle of plant growth in favor of our choice of crops. To make up for this transgression, I recommend the use of a winter cover crop.

Compared to leaving the ground bare, a cover crop cycle improves the quality of the soil by increasing its porousness, which in turn improves the soil’s capacity to retain rainwater. In a climate like California’s, which features a wet winter season followed by a long dry summer, this advantage is critical. High water retention in the spring planting beds mean that plants can grow a deeper and more extensive root structure, allowing them to draw water from deep underground well into the summer. This, in turn, reduces the watering requirements of the plants during the dry summer – an urgent consideration in any drought-prone region. Instead of watching fields lose their rich topsoil to rain runoff overwinter, we can enjoy the benefits of a rich water table throughout the whole season.

Cover crops also provide a big boost to the local ecosystem, encouraging the proliferation of beneficial microbes and invertebrates in the soil. These helpful organisms break down not only the leftover roots from the fall harvest but also the roots and leaves of the cover plants as they go through their life cycle. As all this organic matter breaks down, it enriches the soil with needed nutrients. Compared to leaving fields bare, which encourages runoff and nutrient loss, cover crops can greatly reduce the cost of fertilizer or other amendments in the spring. If the right crops are used, this practice can also fix extra nitrogen into the soil and combat the proliferation of weeds.

Brassicas like these organic collard greens provide human nutrition while preventing soil erosion.

Which crop provides the best coverage?

Which crop to plant depends on the needs of the soil and the plans of the farmer. Some may want to plant a winter garden. This approach has its benefits but generally takes more nutrients out than it puts back into the soil. Fortunately, many delicious food crops can also break weed cycles, add green organic material to the soil, break up hard or compacted soil, and pull latent nutrients up to the surface.

Legumes (plants which produce their seeds in a pod) are great for adding nitrogen to depleted soil. This class of plants includes beans, vetch, clover and alfalfa.

(plants which produce their seeds in a pod) are great for adding nitrogen to depleted soil. This class of plants includes beans, vetch, clover and alfalfa. Rye produces a lot of beneficial biomass and suppresses weeds. Its remarkable extensive root system also does a great job of extending the topsoil layer.

produces a lot of beneficial biomass and suppresses weeds. Its remarkable extensive root system also does a great job of extending the topsoil layer. Brassicas (kale, cabbage, broccoli, cauliflower, and more) produce good food but do not replenish nutrients back into the soil. The same goes for alliums such as garlic and onions, which can yield a delicious harvest before you need the bed space again but does not add nutrients or green organic matter to the soil.

Alfalfa produces beautiful flowers while fixing nitrogen into depleted soil.

How to plant a cover crop?

Generally we plant the cover crop (legumes and rye) by direct sowing, buying seed from a nursery supply company and then scattering seed as appropriate based on the choice of cover crop. It is good to rake in the seed and perhaps apply some mulch so the birds don’t get all of it. Also if winter rains come late, it may be necessary to water a few times to make sure the crop takes root.

If planting a food garden in the winter, we would plant similar to a summer garden, likely with transplanting starts from the greenhouse, or in the case of garlic, planting the cloves directly.

When to plant a cover crop?

Cover crops can be planted any time in the fall or early winter. The sooner the better for some, but of course we must wait for our summer crops to be harvested before our bed space is available. Once frosts have hit too hard, everything grows slower and germination rates drop significantly. Cereal rye is the best for late plantings.

Healthy use of cover crops bring benefits beyond beauty. May every garden produce bountifully, for years and years to come.