Grow Guide: Cover Crops


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In this Grow Guide, we’re going to introduce you to the wonderful world of plants feeding plants. Yeah, that’s right, one more step towards a self-sustaining garden free of chemical inputs!

Cover Crops aka Green Manure aka Living Mulch is a standard organic farming practice that is easy to implement and adds a plethora of benefits to your garden.

Crimson Clover cover crops throughout an orchard in California.

Cover crops have many amazing properties, one of the most important being nitrogen fixation.


Cannabis plants are heavy-feeders, they love their nitrogen. Cover crops, specifically legumes, can create a usable form of nitrogen out of thin air. Legumes have an amazing ability to convert nitrogen that cannot be absorbed by cannabis into a form of nitrogen that is available for your main crop. We surprisingly have an abundant supply of nitrogen all around us, 79% of our atmosphere is nitrogen in the form of N2 gas, however, plants cannot absorb this form of nitrogen. Atmospheric nitrogen requires bacteria or microorganisms to convert the N2 gas into ammonium (N4) or nitrate (NO3) before plants can uptake the nitrogen. Legumes host a specific bacteria that lives on its roots whose sole purpose is to fix atmospheric nitrogen into a usable source and release it into the soil. It’s pretty much plant magic. For grass and non-leguminous cover crops, nutrients are absorbed in the biomass, and once they are turned into the soil, this readily available nitrogen is released, allowing your cannabis plants to feast on a nitrogen buffet.

They smother and suppress weeds


No more weed picking with your cover crops going to work!

Many cover crops grow so densely together that they simply don’t leave enough room for any unwanted weeds to grow (known in the farming community as smother crops). There are even some unique cover crops that contain allelopathic abilities and release a compound that prohibits weed seeds from germinating (plants with superpowers FTW)

They enhance and stabilize soil


Cover crops have been used since the early days of agriculture to help restore infertile land. The crops add healthy organic matter to the soil while their roots act as glue for living soil, keeping it all in tact as you water. This prevents your precious black gold from erosion and runoff.

They help control pests and disease


Plant killed by a soil pathogen.

Many of the cover crops I’m going to list for you in this article develop nectar-rich flowers that beneficial insects and pollinators love. They also provide a shelter and home for these beneficial insects that will help keep the destructive pests in check. Cover crops have also shown success in combatting harmful soil-borne diseases. Some cover crops (mustard, rapeseed, and sudangrass) contain a chemical enzyme in their plant tissue that is toxic to soil-borne pathogens and weed seeds. When these crops are cut and put back into the soil, they destroy hard-to-treat soil-borne diseases.

They add organic matter to your soil


One of the primary uses of cover crops is to remediate soil, and a large part of healthy soil is organic matter. The life of a cover crop is often very short (half a season to a full season max.) When the crop has matured and is about to seed, it is time to cut it down and turn into the soil. There are various ways to do this – some farmers simply pull up the crops and toss them back on the soil while others cut or mow the crop down and then mix them back into the soil. Either way does the job, but many farmers are exclusively no-till so they would opt for the first method. By killing the cover crops and returning them to the soil, all of the nutrients held in the cover crops are released back into the soil, nourishing the soil and feeding your main crop.

They stimulate microorganisms in your soil


Microorganisms will become your best employees. Microorganisms are the ones working overtime to digest the organic matter and turn it into available nutrients for your plants. Your soil can contain all the organic matter in the world but without microorganisms to transform it into something usable it will just sit there and slowly decompose (taking way longer to see the benefits). Microorganisms speed up the process which is crucial for the quick lifespan of the cannabis plant. Microorganisms depend on cover crops for food and shelter. The roots of many cover crops release sugars into the soil where the microorganisms live. An extra bonus – the presence of microorganisms help suppress diseases while improving soil structure!

They are easy to plant, low maintenance and can grow almost anywhere


All it takes is a bag of seeds! Pick your favorite cover crops from the list below, purchase the seeds (I recommend and broadcast them by hand throughout your garden beds or pots. In about a week you’ll see sprouts showing through the soil! Water every couple of days and you’ll have a thriving cover crop.

Overall, cover crops save you money!


They reduce your costs for fertilizers, pesticides, and herbicides while improving the overall health of your garden. Large-scale farmers have saved up to $200 an acre on pesticides and fertilizers by implementing cover crops (cutting pesticide costs up to 40%!).

Before I go into detail of popular cover crops, I want to go through the categories of cover crops:

Legumes are the nitrogen-fixing crops, they include beans, peas, clover, alfalfa, hairy vetch, soybeans, and lentils. Grasses are used for their large amount of nutritious organic matter and their fibrous root system that stabilizes and improves soil structure. Grass cover crops include oats, barley, rye, wheat, and sudangrass. Then there are non-legume broad leaves that provide great green manure, organic matter, and suppression of weeds and pests. This category includes buckwheat, forage radish, brassicas, mustard, and marigolds.

Here is a list of the most common cover crops. Read through, pick the crops that sound best for your garden and get to planting!

crimson-cloverClover is the most common choice for a cover crop because it’s a vigorous, low-lying crop that can easily grow underneath any size cannabis plant. There are a variety of clover types, most often named after the color of the clover flower (crimson clover, yellow blossom sweet clover, white clover, etc.) Most importantly, all types of clover fix nitrogen like no one’s business which provides cannabis with all of its much-needed nitrogen. Clover is also shade-tolerant and will survive through a cold winter.

Growing-Broad-BeansBeans are one of my personal favorite cover crops because they provide you, the farmer, with healthy, protein-rich food while also providing your plants with nitrogen-rich food. It’s a win-win! Every type of bean has nitrogen-fixing abilities – lima beans, black beans, fava beans, burgundy bush beans, garbanzo beans, pole beans, you name it. Once you’ve harvested the beans, trim the plants down to the very base of the stalk, leaving the roots intact to release nitrogen back into the soil.

skills-buckwheat-300_0Buckwheat is best used as a smother crop because it successfully out-competes pesky weeds. Buckwheat is a very vigorous cover crop, growing from seed to flowering in as little at six weeks. While buckwheat does have nitrogen-fixing abilities, it needs to be planted in an area that previously grew a nitrogen-fixing crop to jumpstart the buckwheat’s nitrogen process. However, unlike other cover crops, buckwheat absorbs phosphorus which is released upon its return to the soil. Buckwheat also produce beautiful flowers that attract beneficial insects.

peas_field__mediumField peas are also called Austrian winter peas (black peas), Canadian field peas (spring peas). Peas can be planted in both the winter and the summer depending on the species. Field peas are known for their high nitrogen-fixing abilities. Peas are a favorite amongst growers because their stems and leaves break down quickly to release nutrients fast. Field peas are often combined with oats for a dynamic duo that oozes benefits for your garden.

scn321aOats are a quick-growing grass cover crop that will provide a plentiful amount of organic matter which is a crucial component of healthy, living soil. Oats are great at suppressing weeds, taking up excess soil nutrients, and can actually improve the productivity of legumes when planted together (hence the oats and field peas combination). They are not winter-hardy so this is a crop to plant in spring, summer, or early fall.

IMG_40241Barley is an inexpensive and easy to grow grass cover crop. It adds a lot of organic biomass (more than any other cereal crop) which helps restore overworked, infertile soil. Barley helps protect and stabilize topsoil while providing excellent erosion control. As a winter crop, barley develops a fibrous root system that can reach 6.5 feet deep, helping to break up compacted soil layers.

Hairy-VetchHairy vetch is the go-to cover crop for the winter season. It fixes large amounts of nitrogen that help supply the needs of the following spring crop. Vetch is hardy enough to survive in areas with hard freezing and goes to work all winter long fixing nitrogen at a rate of 100 lbs or more per acre. Plus, when spring rolls around, hairy vetch decomposes and releases the nitrogen quicker than other cover crops (while also suppressing weeds).

968GWinter Rye (cereal rye) is another easy-to-grow grass crop. It’s often hailed as the best winter cover crop because it will survive through frost. However, it’s not exclusively a winter crop; it can also be planted in the spring for spring/summer companion plants. One of the most amazing characteristics about rye is that it has an allelopathic effect on weeds, meaning rye actually exudes a compound that suppresses the germination of weed seeds, significantly reducing the spreading of unwanted weeds.

Field Mustard (Brassica rapa) Santiago Oaks Regional Park, Orange, CA) 1-20-08 036Brassicas (mustard, rapeseed, forage radish, and kale) are non-traditional cover crops that have been gaining popularity. These are great for the fall as they will naturally die off in the winter or you can harvest for some fresh, organic produce! Forage radish has peaked the interest of many growers because it grows vigorously and quickly with a large taproot (1-2 inches in diameter) that can drill through dense soil and help break up compacted layers. Brassica crops are also successful in suppressing soil pathogens and pests, particularly destructive nematodes.


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