“A farmer’s work is never done” is a saying that is all too true when working with cannabis. After you’ve harvested your last crops for the season and the garden beds are empty, you can continue to nurture the soil you’ve worked so hard to develop. Cover crops are an age-old farming method used to maintain and improve the soil you raise your plants in. Also known as “green manure,” cover crops benefit your soil in a variety of ways:
- Prevent erosion
- Sequester nutrients
- Reduce soil compaction
- Suppress weed growth (well, the weeds you don’t want)
- Repel unwanted pests
- Provide habitat for beneficial organisms
But what is a cover crop exactly? Simply put, a cover crop can be any type of plant that is used to protect and improve the soil and environment for the next farming season. In the wild outdoors, the ground is rarely ever bare; generally, something is always growing throughout the year unless it is buried in snow. Using cover crops mimics nature and keeps your ecosystem thriving through the off-season.
Personal preference is but one factor when it comes to choosing the right cover crop for your garden. Below is a list of some of the most popular cover crops, each of which benefit your soil in unique ways.
Commonly Used Cover Crops
Rye grass is a great option for a winter cover crop, as it can germinate in colder temperatures (34-40°F) and survive frost. This cover crop grows deep, penetrating, and fibrous roots that will help lock nutrients into the soil, prevent both nutrient and soil runoff during wet winters, and improve the overall soil tilth. These roots also absorb nitrogen, which can be returned to the soil by tilling or composting the cover crop. Another benefit of using rye as a cover crop is that it has negative allelopathic effects, which means it releases compounds that prevent weeds from germinating.
Winter wheat is like rye grass in that it helps prevent nutrient and soil runoff during the winter months. It grows vigorously while overcrowding competing weeds. Some gardeners choose winter wheat over rye because it’s easy to kill in the spring, allowing you to wait later to till or chop down. The longer you can let your cover crops grow, the longer you can protect the nutrients and soil from erosion.
Clover is a nitrogen fixer, meaning it sequesters nitrogen into the soil for your cannabis plants to use later. Clover can be grown with cannabis plants as a companion crop, or it can be grown during the off-season (spring or late winter). Its roots are shallow, but they still work to improve the soil’s quality and prevent topsoil compaction.
As a cover crop, mustard works in the early fall or springtime to prevent diseases and pests from developing in the soil. It does so through a process known as “biofumigation” where pungent glucosinolates are released from the plant when they are chopped down. Mustard is simple to work with and easy to cut down before the next grow season.
Hairy vetch is one of the more productive nitrogen fixers available as a cover crop. It needs to be planted by early fall to take hold, but will then work to bring nitrogen into the soil until late spring. Hairy vetch is strong, resilient, and produces a quality root system that keeps your soil happy and healthy over the winter months.
Beans are a nitrogen-fixing legume that will help improve the quality of your soil. Planted in the fall, beans require soil that is rich in phosphorus, calcium, and sulfur to thrive and develop over the winter months. Once spring rolls around, you should be able to harvest the beans, mulch the plants, and spread them over your garden beds.
A less traditional cover crop, kale is a hardy source of food that will grow through mild winters. While it doesn’t fix nitrogen, kale roots will sink into your soil and protect the valuable structure you have created, all while producing a quality food source for consumption. Maximize this plant’s productivity by using leftover amendments from the grow season to top dress your soils.
Every cover crop has unique properties, but the baseline value remains the same: Your soil will be much happier and alive if you give it plants to work with year-round. If you leave your soil unattended, you lose the biodiversity your plants love while also surrendering nutrients to runoff. If you are still unsure of what cover crops to use, your local nursery should have recommendations specific to your needs and climate.