Cover Crop Basics

Adding a cover crop to the home vegetable garden was a game changer for me, and the garden has been happier ever since. Planting cover crop seed is an easy and effective way to practice good soil health on any scale. There are a few tips and tricks for having the best luck for home gardeners. Timing and seed selection are key!

There are many different ways of cover cropping, from holding a field for a full year, or part of spring or over the winter. Because I succession plant so much of my garden space from early spring to past the frosts of fall, I don’t leave much of my soil bare at any one time. But one of the reasons I have incorporated cover crops is how easy it is to just sow the seeds once I’ve harvested a late summer crop.

There are also a few different reasons people plant cover crops to benefit the garden. One is to build up organic matter in the soil. Another is using legumes to add nitrogen to the soil (or directly to the plants if grown simultaneously). A final reason is to help break up compacted heavy soil with plants that have think roots. If left to rot they create wonderful space in the soil for nutrient and water transfer. Basically, cover cropping is another way of Companion Planting for your garden.

Soil Health Starts with Cover

It always helps me to know the WHY behind whatever I’m doing- so… before I started planting cover crops a few years ago I took a deep dive into soil health. Asking, “Why are we planting seeds in the fall when they won’t have time to mature?” The basic answer is soil health.

When bare soil is pounded by rain it compresses it making it harder for roots, worms, nutrients and even water to penetrate. When bare soil is baked by the sun, it dries and cracks. Any existing soil life moves deeper down under ground and the existing organic material becomes stagnant and lifeless.

Adding a mulch like straw or leaves keeps a protective barrier on top of the soil, preventing both compaction and drying. Organic mulches (leaves, straw) will also decompose over time adding organic matter in the soil, making it even more inviting for more varieties of soil life. So, if you decide growing a cover crop isn’t something you want to do, try adding a layer of mulch to that bare garden soil instead, your soil will reward you the following year!

On a large scale, we can see carbon dioxide levels rise after farmland is harvested and tilled- and the soil is left bare for months. The levels above the same areas drop drastically once crops start growing again in the spring. If you want to be wowed at the power of plants to create carbon sinks, watch this time lapse video from NASA.

Planting Cover Crops to Build Soil

When we feed the soil we keep it alive.

Cover cropping is a way to grow your own mulch which feeds the soil in different ways from organic mulches. By choosing which seeds to plant you can choose what to feed your soil. Most home gardeners are looking to add some nitrogen, organic material and maybe help with breaking up the soil a little with their cover crop.

 I find great results with a seed blend of oats, peas and radishes. Specifically, a blend with these three seeds called Nitro Max Mix from Albert Lea Seed has done well for me. 

The oats create a thick mat of mulch keeping weeds down the following spring (see the notes on allelopathy below). The peas add nitrogen and the radishes break up the soil a bit more. I also blend my own with organic seed from my local feed mill. Locally, I know that EggPlant Urban Farm Supply also carries cover crop seed.

Another winner for home gardeners is Buckwheat. This plant is easy to cut back – but should be cut before the seed heads form so it doesn’t re-seed. Buckwheat is usually planted in the spring before a later succession of heat loving crops like tomatoes, peppers or zucchini. You can both leave the cut stalks or work into the soil.

I keep wanting to try crimson clover but haven’t grown it yet myself. I wanted to mention this seed, as it is a wonderful way to add nitrogen (it is a legume). It can also be used as a living mulch. This is a great choice for attracting lots of pollinators.

How I Cover Crop

In Minnesota, I most often plant cover crops in the fall, right after I’ve harvested something that required more digging than my normal no till practices, like potatoes. Since I’m already digging into the soil it feels natural to plant something else into it rather than practicing strict no till gardening. For more information on how to start a no till garden read my full post on that HERE. Plant in time for these crops have five to six weeks of grow time before frosts would kill them off.

That’s another reason I prefer an oat-based cover crop- they always winter-kill. This is often a concern for home gardeners thinking about cover crops. With plants that die with freezing temperatures you don’t have to worry about the cover crop self-seeding the next season.

Direct seed into soil that was recently harvested from. I usually plant out in mid-September. Water and let it grow. I often use a wire covering over the freshly planted seed to keep pests from digging into the soil. In the spring you’ll find a nice mat of dead mulch on top of the soil. A thick root mass still intact under the soil. These roots have kept a whole host of soil microorganisms happy over winter. This soil life would have had nothing to feed on and left otherwise.

I tend to plant transplants or larger seeded crops into these areas to leave as much of the soil as possible undisturbed come spring.

If you do need to till in the cover crop, you’ll need to wait three to four weeks to plant. Tilling in the dead plant matter will alter the soil activity to the point where your new transplants or seeds won’t do well.

Allelopathy Explained

Allelopathy is another way to harness the power of cover crops. This is a process when a plant secretes growth inhibiting compounds from its roots. Even cucumbers excrete a growth prohibiting chemical via their roots. But most people use this chemical warfare to their advantage with crops left in the ground. Oats are a great example of the straw creating a wonderful mulch while also leaving a residue that prohibits other plant growth.

General Benefits of Planting a Cover Crop

• Better Water Retention – soil with root mass holds more water
• Less Weeding – soil that is covered keeps weed seeds from germinating
• Reduced Disease – soil life diversity increases disease resistance
• Less splash up – having a physical barrier between the soil and plants reduces pathogens from infecting plants

Living Mulches

A living mulch is anything that keeps down other plant growth just by growing itself. It is worth mentioning within cover cropping simply because it is another sustainable way to keep the ground covered while feeding the soil life. I’m a firm believer in planting Dutch white clover in my garden paths. I’ve had great success with bringing in even more pollinators adding clover. Now the clover is slowly taking over the old grass. It requires less mowing and is easier to weed out of edges of gardens compared to the old existing lawn. Living mulches can also be used to simply shade out other plants.

Bottom line is to keep your soil covered for happier plants and a better harvest. So, tell me- have you cover cropped or will you now? What other questions do you have about planting a cover crop in your home garden?

Dig In,
Michelle