What is a Cover Crop?
The term “cover crop” is often used as a catch-all for plants whose main purpose is not to yield a food crop but rather to provide desirable benefits to your soil and the actual food crops planted after them. Cover crops are commonly used and associated with industrial farming operations but in recent years gardeners have started to realize their usefulness in personal gardening.
Benefits of Using Cover Crops
The most important benefit gardeners get from cover crops is that they act as a natural weed suppressant. They accomplish this in one of 2 ways. The first is by simply covering the soils surface so small weed seeds like crabgrass or pigweed don’t have the space and sunlight they need to grow.
The second way some cover crops suppress weeds is through allelopathy. Allelopathy in a nutshell is when a plant produces certain chemicals with the express purpose of disrupting the germination, or inhibiting the growth, of other plants around it as a means of chemical competition. This reduces the need for manual weeding or the use of harmful herbicides saving you time, money, and labor all while keeping your garden looking neat and tidy.
Furthermore, some cover crops improve soil fertility by fixing nitrogen. As I’ll explain more below, crops in the legume family have the ability to fix nitrogen into the soil and as a result food crops planted after a legume cover crop grow healthier and produce higher yields.
Types of Cover Crops for Vegetable Gardens
Now that you understand the benefits of using cover crops, let’s explore the different types.
Legumes
Legume cover crops, such as crimson clover and hairy vetch, are excellent choices for enriching the soil with nitrogen. They have the unique ability to form nodules on their roots that house nitrogen-fixing bacteria. These bacteria convert atmospheric nitrogen into a usable form. You can think of them as the supplementary “N” for nitrogen in the NPK macronutrients your plants need.
Grasses
Grass cover crops, like rye and oats, are great for adding organic matter to the soil. They have deep root systems that help break up compacted soil, improve drainage, and prevent erosion. Grasses also act as green manure, enriching the soil with essential nutrients as they decompose. As with all cover crops it’s important to use annuals and not perennials. Otherwise, you will turn your entire garden into a yard. :)
Brassicas
Brassica cover crops, such as mustard and radish, are known for their bio-fumigation properties. When these plants are terminated and left to break down into the soil, they release natural compounds that suppress soil-borne pests and diseases. Brassicas also help improve soil structure by penetrating deep into the soil with their taproots.
Planting and Growing Cover Crops in Your Vegetable Garden
Now that you understand the types of cover crops out there, it’s time to get your hands dirty and start planting!
Site preparation
Before planting cover crops, clear the area of any debris or weeds. Optionally you can choose to loosen the soil with a garden fork or tiller to ensure better seed-to-soil contact.
Seed selection
Purchase high-quality cover crop seeds from a reputable supplier and follow the instructions on the seed container for the recommended seeding rate and depth. While you can buy pre-mixed cover crop seeds, you can also purchase individual cover crops and mix them later. Doing so allows you to mix the exact varieties and amounts to meet your needs.
Planting method
For the small vegetable grower, the best and easiest method is just good ‘ol fashioned broadcasting. This involves spreading seeds evenly across your growing area and then watering them in. You can do this with a hand-crank spreader or you can simply spread the seeds by hand.
Pro Tip #1
Cover your newly spread seeds with a thin layer of compost after they are watered in. This layer provides needed nutrients to the soil and helps keep the seeds moist to ensure even germination. It also hides your seed from the birds!
Pro Tip #2
You can optionally soak your seeds in water for 12 - 24 hours before planting. This will shave a day or two off of the germination time and reduces the amount of watering you will need to do to get your cover crop established.
Managing Cover Crops for Maximum Benefits
To maximize the benefits of cover crops, proper management is key. Be sure to consider:
Timing of termination
Cover crops should be terminated before they set seed or become too mature. This ensures that they do not compete with your vegetable plants for resources or become a nuisance. The best time to terminate a cover crop is when it begins to flower. At this stage most cover crops begin to dedicate a lot of their resources into seed creation and terminating them at this point helps to ensure they will not regrow.
Termination methods
There are 3 main methods for terminating cover crops which are mowing, tilling, or winter kill. The first two are referred to as mechanical termination and the last is simply using the cold winter temperatures to terminate crops for you. If your area receives sufficiently cold winters, winter kill is a viable option for you. However if you live in a place where winters usually do not get cold enough to kill your cover crop, or it can withstand very cold temperatures like crimson clover, then you will need to use mechanical termination in the spring.
Incorporation into the soil
After termination, you can choose to till your growing area and incorporate the cover crop residues back into the soil. However, if you do not want to till your soil, you can simply use the bagger on your push mower to collect the residue and then put it back on top of the soil to let the organic matter break down over time. Sometimes you will find that there is still some residue on the top of the soil that did not break down sufficiently, simply clear off the remaining residue with a rake and add it to your compost pile.
Tips for Integrating Cover Crops into Your Vegetable Garden
Integrating cover crops into your vegetable garden can be a game-changer. Here are some tips to help you seamlessly incorporate cover crops into your gardening routine:
Plan ahead
Consider cover crops when planning your garden layout and crop rotation. Determine which areas will benefit from cover crops and schedule their planting accordingly.
Start small
If you are new to cover cropping, start with a small area to gain experience and assess the results. Once you feel confident, gradually expand the coverage to other parts of your garden.
Experiment
Don’t be afraid to experiment with different cover crop combinations and planting methods. Every garden is unique, and what works for one may not work for another. Keep a gardening journal to track your observations and learn from each experience.
Final Word
Using cover crops in the garden is a simple and completely organic way to provide many primary and secondary benefits for you and your garden. Using cover crops does require some planning, expense, and garden space, but it’s a worthwhile tradeoff to help build a productive garden that can provide healthy food for you and your family. So please do yourself a kindness this next growing season and give cover crops a try!