If you’re growing a kitchen garden (regardless if it’s organic or not), there’s a good chance that the produce you are growing is depleting the soil. That’s how it works. Many of the nutrients in the soil are transferred into the crops as they grow; it’s what makes our food grow big. The problem with farming and gardening practices that don’t return nutrients into the soil often enough is that overtime the soil get’s depleted, then dies, and nothing can grow. If nothing can grow, then carbon in the atmosphere lingers which leads to a whole host of negative reactions in the environment. In addition to humanity’s extreme CO2 emissions, this is a large contributing factor to our planet’s rising temperatures: the lack of carbon-sequestering and biodiverse ecosystems due to deforestation, development, and poor agricultural practices.

One of the most powerful things we can do as gardeners and eco-minded citizens is to actively steward the creation of soil-regenerative land that invites high biodiversity and traps carbon from the atmosphere. How do we do that? Enter cover crops. In this informative post I’m teaching you all about cover crops, their many benefits, and how you can incorporate these wonder-plants into your garden.

White Dutch Clover Seed from True Leaf Market

What is a Cover Crop?

Cover crops are seeds that are planted en masse for several reasons that benefit the soil and garden ecosystem. Most often cover crops are grown in rotation with our typical garden crops to protect and rejuvenate the soil, a practice that goes back centuries.

The Native Peoples in America developed the method called “The Three Sisters Planting”. Beans, squash, and corn were planted together to work symbiotically. Beans are a cover crop and cycle nutrients through the soil which enable the corn and squash to grow big. In China, Chinese milk vetch another plant in the legume family is planted just after a rice harvest in the same ground to act as a mulch and return nutrients to the depleted soil.

The Benefits of Cover Crops

There are countless more examples of indigenous cultures across the world utilizing cover crops for multiple purposes. They attract pollinators which aids in building biodiversity, prevent erosion, protect against soil compaction, preserve moisture, and suppress weeds when growing. When cover crops are mowed down to decay, the plant material adds biomass to the soil which improves soil texture and drainage. At the same time, nutrients are cycled back into the soil which vegetable plants can use as a food source without needing a chemical fertilizer. Think of them as a green manure - they offer the same benefits as livestock manure. Cover crops return nitrogen to the soil, but most notably through a process called “nitrogen fixing” where the plants convert the nitrogen from the air into the soil. Nitrogen is a key food source for plants and the main ingredient in chemical fertilizers.

Today, fertilizers overshadow the use of cover crops, but these ancient indigenous ways of utilizing cover crops are making a comeback as some growers are learning how cover crops not only keep soil healthy and organic, but cut down on the reliance of pesticides.

All of these benefits of cover crops add up to creating an incredibly robust environment that enable plants to thrive. Thriving plants provide habitats for a variety of insects and animals. Plants also inhale Co2 from the atmosphere, transfer it to the soil where it’s fed upon by soil organisms, then exhale oxygen. This whole process creates a biodiverse ecosystem and micro-climate in our very own landscapes that help bring balance to our environment.

What types of plants are cover crops?

Legumes: Alfalfa, Clover, Chickpea, Soybean, Pea, Fava Bean, Hairy Vetch, and Lentil

Legumes are the primary nitrogen fixers of the cover crop world. While other seed types return nitrogen through decaying matter, legumes convert nitrogen from the air and return it to the soil. Their strong and pervasive root system also breaks up compacted soil (natural tiller) which creates pathways for oxygen, water, and life to move.

Brassicas: Radish, Mustard

Mustard and radish help significantly control pests because they contain a high amount of glucosinolate, a natural chemical compound that wards off harmful insects. Mustard and radish grow quickly in the cool seasons, which makes them an ideal weed suppressor in early spring and fall, or during winter for mild climates. Diakon radish grows long thick taproots which act as incredible natural tillers for compacted clay-like soil.

Grains and Grasses: Wheat, Rye, Barley, Oat, and Triticale

Grain cover crops are great protectors of soil while also scavenging for nitrogen and potassium - two macronutrients plants need as food. Grains and grasses produce a wealth of biomass to the soil when terminated between crop rotations.

Broadleaf Species: Buckwheat

Broadleaf cover crops include both legumes and brassicas that produce wide protective leaves. Nearly all flowering cover crops are broadleaf species. Broad leaf species are best used if you want to shade out weed and attract pollinators.

Cover Crop Mixes

Different varieties of seed are combined to create unique cover crop mixes. Sowing a mix is an excellent way to utilize several benefits of different crops so they work in tandem. I’ll be sowing a cover crop mix in my kitchen garden to grow throughout fall and winter.

cover crops and why you should plant them in your garden.jpg

How to sow a Field of Cover Crops

In these images I’m sowing a field of clover around my kitchen garden. This low-growing white dutch clover will act as a beneficial cover crop to the orchard I’ll plant this fall. The root system will soften the compacted soil, draw in nutrients, act as a living mulch, and a green manure. It will also double as a drought-resistant lawn alternative. I’m growing this clover as a permanent perennial ground cover. Requiring less maintenance than a traditional lawn, the low-growing blooms will attract pollinators and be soft to walk on barefoot when blooms are mowed.

When I built my kitchen garden rows I sowed buckwheat to improve soil nutrients, tillage, drainage, and soil texture. They grew fast in the heat which caused them to shade out weeds and attract pollinators. Currently they’re adding biomass to the soil since they’re spent and I’ve I cut them down. When I winterize my garden I’ll cover the rows with compost, then sow my fall crops (such as garlic) and a cover crop mix over the whole garden to continue regenerating my soil throughout winter.

Step 1: Kill + remove all grass weeds

This can be done by weeding by hand in smaller gardens. For large areas like mine, laying cardboard or a black tarp over the whole area for 3-4 months during the summer is the best way to solarize and kill the weeds completely. Alternatively, a natural weed killer can be sprayed. If you are killing grass and weeds in large field, this will need to be done repeatedly once a week for 3 months during peak temperatures in the summer. It’s imperative to completely remove all weeds and grass otherwise they’ll overtake the new seed.

Step 2: Layer on top soil + compost

The new seed will need soft, nutrient-rich soil to germinate. Layer on 3-4 inches of high quality garden soil + compost over the whole area. Rake to smooth and refrain from walking on it as much as possible. You’ll want to keep it as fluffy as possible.

Step 3: Mix seed with Sand

This mixture will enable you to toss the seeds over the soil and visibly see where it lands. It will help you sow the area evenly. The ratio depends on the seed, but a general rule of thumb is about 10:1 (sand:seed). This is best done only if you are broadcasting the seed by hand. If you use a broadcast seeder, then you don’t need to mix the seed with sand. If you are sowing a smaller area, say a raised bed, or a garden box, this step can also be skipped.

Step 4: Broadcast the seed

A broadcast seeder can be used, or you can toss the seeds by hand. Pass over the area lightly first, then go back and reseed thin areas. This will ensure you don’t run out of seed too soon.

Step 5: Tamp the seed down

After seeding it’s best not to walk in the area because you don’t want to damage the seeds or compact to soil too much. Tamp the area down by walking on boards. Boards help distribute your weight evenly so it doesn’t crush the seed, it simply pushes them into the soil so they have something to latch into. Tamping yields stronger germination results.

Step 6: Water Thoroughly

Different seed varieties germinate at different rates under different environmental conditions. Be sure to water immediately and keep the areas consistently moist until seeds reach maturity. Watch the weather and plan this event when weather is mild.

*To sow cover crops in garden rows or backyard garden box, follow these same steps. It’s best to do this soon after harvesting your crops in late summer, fall, or early spring. I’ll continue to share more on this process as I utilize cover crops in my kitchen garden, so stay tuned for more.

Planting Cover Crops in Spring vs. Fall

Cover crops are best used in between growing seasons, such as overwinter, before spring planting, or between the summer and fall growing seasons. Spring Cover Crops are often planted in the early spring and allowed to grow until a few weeks before planting when it is mowed down. At that point, seeds are sown and starter plants are transplanted directly into the cut down crop.

Fall cover crops are planted when summer temperatures are waning, giving the cooler season seeds time to germinate in the necessary autumn conditions. Once mature, usually around the first frost, these cover crop varieties are mowed down and allowed to decompose over winter.

Some varieties of cover crop seeds are sown in late fall after the first frost and allowed to lie dormant until early spring when they germinate.