Cover Crops For Gardens: what are they and how do I choose one?

Cover crops are one of the most important tools in the organic gardener’s toolbox. Although it might seem wasteful to grow plants that you won’t eat, the benefits to your garden are well worth it. Cover crops protect the soil, help improve soil structure and provide you with all the organic matter you need.

Using cover crops successfully isn’t difficult. Cover crop plants are easy to grow and don’t need much fuss. If you want to introduce cover crops into your gardening strategy, make sure to keep reading.

In this article, I’ll share with you what cover crops are, the benefits they’ll bring, and how to use them in your garden. You’ll be surprised by how big a difference an easy planting of cover crops will make. You might even find that some of the weeds growing in your garden are already serving as cover crops!

What is a cover crop?

A cover crop is a plant that is used to protect the soil while it’s not being actively used. They are plants grown for the soil, not for human consumption. Cover crops can fix nitrogen into the soil, provide organic matter, prevent erosion, improve soil structure, suppress weeds and protect microbial soil life. Most cover crops are either legumes, grains, or broadleaf plants.

Legume plants have symbiotic relationships with soil bacteria, allowing the plant to fix nitrogen previously inaccessible to plants into the soil. As they grow, legumes fertilize the soil. They can then be cut down in place to be used as mulch or get turned into the soil.

Grain plants, on the other hand, have deep root systems. The deep roots aerate the soil, loosening it and providing channels for air and water. Grain plants also tend to be tall, helping water penetration in the soil by slowing the rate at which it hits the ground. And of course, lots of green material for the compost.

As the name suggests, broadleaf plants are grown for their fast growth and big leaves. Their role is to establish themselves quickly and shade out or out-compete the weeds. Broadleaf plants will also provide you with heaps of organic material with which you can mulch or compost.

In essence, cover crops are any plant that is grown to be cut down before providing food. Their purpose is purely strategic. You might find that you unknowingly already have cover crops in your garden. Maybe something like clover? 

Why would I use a cover crop?

Cover crops can be one of your greatest tools in the garden. You can use a cover crop to cover the soil, suppress weeds, loosen compacted soils, for organic material, and as fertilizer. In the end, cover crops make you a more self-sufficient and experienced gardener.

The main reason you would use a cover crop is to seed a bed you don’t intend on using productively. This normally happens in the winter months since there are way fewer cold-season crops. Edible plants come out and the bed is seeded with cover crop seed.

If you’re experiencing weed, soil, or nutrient problems, you can use cover crops to meliorate the situation before planting. Cover crops normally have strong growth, and if planted at the right time they can establish quickly and outcompete annoying weeds. It won’t eliminate your weed problem, but you’ll be dealing with fewer and smaller plants.

Did you know that soil compaction can be improved just by planting in it? Cover crops in the grain family are excellent for reducing compaction and improving aeration. Their strong, long root systems create channels for water, air, and future roots to go through.

Many gardeners use rye or wheat for their grain cover crop, but I actually prefer amaranth for its stunning colors. Who said cover crops can’t also be ornamental!                       

Legumes are the most common cover crop to encounter because of their unique ability to fix nitrogen into the soil. The air is full of nitrogen, but it’s not in a form accessible to plants. Thanks to partnerships with a bacteria (which will eventually release the plant-accessible nitrogen into the soil when they die) legume plants can convert airborne nitrogen into fertilizer. 

Other plants, such as comfrey, are bio accumulators (meaning they bring up nutrients from deep in the ground). Another awesome source of garden-grown nutrients. 

I use cover crops to provide me with materials that I would normally have to buy. Cover crops allow me to take advantage of land I’m not actively using to become increasingly self-reliant. I notice this the most when it comes to organic matter for the compost.

In any garden, the biomass (organic matter) you create is like gold. Organic remains of last season’s plants decompose and become food for future plants. This closed-loop system builds the healthiest soils and supports a thriving ecosystem. In the end, a healthy garden means less work for the gardener.

Can I use a no-till cover crop?

All cover crops are no-till crops and are actually a key component to a no-till gardening strategy.  If chosen correctly, cover crops can do many of the same things as rototillers without disturbing soil layers. But it can be daunting to think about managing so much plant mass without heavy machinery.

Edible garden cultivars tend to not do well in crowded conditions and won’t outcompete the cover crops. So if you choose a no-till approach you must manage your cover crops a little differently. You’ll need more patience and time, but in the end, it will be less work.

Managing cover crops with no-till methods involves good timing and some waiting periods so cover crop plants die in time.  There are three main ways to kill a cover crop without a tiller. These are to let the cold of winter do it, let plants complete their natural lifecycle, or deprive them of light and water.

If you live in an area with cold, below-freezing winters – lucky you! The cover crops will die on their own. However, if you’re like me and need to manually kill them, I’ll share how I do it in my garden.

The first step for me is to trample the cover crop with a snowboard-like contraption. Then I cover the crops with a thick black tarp. The tarp stays over the cover crop for a few weeks until I’m sure it’s dead. Pulling back the tarp at the end reveals an already-mulched bed that is ready to be planted.

The biggest thing to note is to never let your cover crops go to seed. If they begin to flower, but you’re not ready to plant, use a chop and drop method. Chop and drop just means that you’re chopping off the top part of the plants to remove the flower. What you remove can just fall to the ground and be left to decompose.

When should I sow a cover crop?

Cover crops are usually sown after edible crops have been harvested. Most commonly, this happens after summer crops come out to protect the soil over winter. The crops are then rolled and killed in the spring with just enough time to plant.

Sometimes a second round of cover crops is planted in the early spring, as soon as the ground thaws. Spring-planted cover crops will grow until early summer where they can be replaced with late summer vegetable transplants.

In my region, winters don’t freeze so I can pretty much grow year-round. However, I always like to dedicate about ½ my beds to growing cover crops over the winter. Come spring, I’ll have tons of organic matter to work with.

If you are using cover crops for weed suppression, you’ll want to plant them up to a year before you intend on planting. This also applies to increasing soil fertility (as long as you chop and drop legume plants before they go to seed).

How do I choose the right cover crop for my garden

To choose the right crop for your garden you’ll need to define what your needs and expectations are. What season you plant in, the amount of time you want the cover crop to stay in the ground, and the requirements of your soil are just some things to consider.

I believe that maximum diversity is important for everything in the garden, cover crops included. By choosing a variety of cover crops, you can take advantage of their different beneficial properties.

In my garden, I use a combination of vetch, peas, oats, sunn hemp, and amaranth. For the pathways, I like a nice carpet of clover on which to walk through.

This combination works for me because I have mild winters, hot summers, long growing seasons, fairly good soil, and a small space. Based on your conditions (and what seeds are available to you), you’ll want to choose your own.

Summary

Deciding to start growing cover crops was one of the best decisions I ever made. At first, I wasn’t convinced that the effort of growing plants I wasn’t going to eat was worth it. Now I know that it actually saves me an enormous amount of time, energy, and money.

If you want to maintain an organic, low-impact garden, cover crops are essential to your strategy. They will provide you with mulch, biomass, and will fertilize the soil. Certain cover crops can even deter pests and diseases!

The most important role of cover crops, however, is the preservation of the soil. In conventional agricultural systems, planting areas are left exposed between crops. Not only is the soil not exposed when using cover crops, but many plants used for cover cropping will also break up compaction, improve aeration, support soil life, and make nutrients available to future plants.

The last thing I’ll say about cover crops is that they do need some planning to work successfully. Spend an afternoon figuring out what dates you need to do what, and you’ll be good to go.

Further reading:

https://ahdb.org.uk/cover-crops