Top 4 Reasons To Plant Cover Crops In Your Raised Beds

Raised beds are a common way to grow vegetables and flowering plants when either space is limited, bending down is difficult or natural soils are poor and compacted.

They offer many benefits such as improved drainage, better soil quality, earlier growing season and easier space management. One question gardeners often ask is what should I do once I've harvested my vegetables and flowers or in areas that I don't currently have a use for?

The answer is easy....plant a cover crop!  

Cover crops, also known as green manure, are plants that are grown primarily to benefit the soil and wildlife rather than for harvest. These crops are sown to cover and protect the soil during periods when it might otherwise be left bare, to specifically improve soil health or to create temporary habitat for wildlife such as pollinators.

Here are the top four reasons you should plant cover crops in your raised bed gardens and how to do it easily.

1. Increased Soil Life

When cover crops are planted, you maintain active roots in the soil during a period that typically lacks them. Soil microbes and other soil organisms like earthworms and insects, essential for converting organic matter into nutrients, prefer residing on or near living roots. When raised beds are not utilized for growing vegetables and other plants, cover crop roots provide a habitat for these soil dwellers.

Additionally, the introduction of cover crops enhances plant diversity, creating a favorable environment for microbial diversity. Consequently, a more diverse community of soil life contributes to the improved cycling of nutrients, energy, and water for the subsequent growing season's crops.

Additionally, cover crops help regulate unwanted microbes and pests, preventing them from becoming potential issues.

2. Soil Protection

Cover crops play a crucial role in keeping the soil within raised beds protected. The presence of living plants and the residues they leave behind assists in moderating soil temperatures, maintaining moisture levels, preventing wind erosion and .

These plant materials also act as interceptors for raindrops. This interception ensures more water infiltrates the soil, preventing soil displacement and erosion from the raised beds.

Cover crop of buckwheat & vetch cover the soil and prevent weeds from growing

3. Weed Suppression 

Most cover crop species have a fast germination period and quickly form a dense canopy. This dense canopy shades the soil, making it harder for weed seeds to germinate and grow. This natural weed control reduces annual weed seed production and lowers the number of weeds that will germinate during the next growing season.

As well, difficult to control perennial weed species like thistles and dandelion that have seeds blown in by wind are prevented from taking hold and causes future weed problems. For raised beds that have perennial weeds already present in a growing bed, aggressive cover crops help suppress them and prevent spreading.

4. Improved Fertility

Many cover crops are legumes (e.g. clover, vetch and peas) and have the ability to form a symbiotic relationship with nitrogen-fixing bacteria. These bacteria take atmospheric nitrogen and convert it into a form that plants can use, thereby increasing the nitrogen content in the soil. This process is particularly beneficial for subsequent crops that have high nitrogen requirements.

Other cover crops are nutrient scavengers (e.g. daikon radish, buckwheat and grasses) and they have the ability to find nutrients from the lower depths of the soil and bring them up to the surface. As these plants die and decompose, they release the nutrients they have accumulated, feeding the soil and crops grown after them.

Simple Planning

A little bit of simple planning can go a long way in getting the most out of planting your cover crops. Try to align your species choices with the seasons when the raised beds are not utilized for vegetables or flowers.

Select cover crops based on their suitability for addressing specific needs, such as alleviating compaction (e.g. daikon radish), enhancing fertility (e.g. crimson clover), increasing organic matter (e.g. annual ryegrass), improving water retention (e.g. fall rye), and so on.

Cutting buckwheat cover crop at 50% flowering
 

Termination

It is important to terminate cover crops at the right time. Typically this means cutting or mowing the plants before or at the 50-80% bloom stage. Most growers want to avoid allowing the cover crop to go to seed, as this could lead to volunteer weeds germinating during the next growing season. In some cases, cover crops can be left past flowering in order to allow self-seeding or if perennials (e.g. red clover or alfalfa) are planted and a longer growth period is desired.

The termination process for the cover crop depends on the size of the raised bed. For small to medium raised beds, use shears to cut the cover crops at the base of the plants. For larger raised beds, a weed-wacker, lawn mower or roto-tiller can be used. Plant materials should be spread evenly or incorporated over the entire soil surface.

Plant materials can either be cut into small pieces for faster decomposition and ease of planting afterward or left as whole plants for slower decomposition and a thicker mulch.

Broadcast planting of cover crop seed mid-summer

Easy to Grow

Cover crops are exceptionally easy to grow and can be planted in various spaces, regardless of size. Whether in mounded beds, enclosed raised beds, raised beds on stands, or even window boxes, cover crops prove beneficial in maintaining soil health and promoting sustainable gardening practices.

Most species can be broadcast onto the surface, lightly pressed into the soil and watered. They germinate very quickly and require very little care once planted, making them very rewarding to grow!

For more information on cover crops, visit our other Cover Crop Articles.

About the Author: John Côté owns and operates John Boy Farms with his family who have been farming the same land for over 140 years. As an agronomist and experienced farmer, he helps others learn how to grow garlic and cover crops successfully. He has written many articles and is the author of The Master Guide to Growing Big Garlic.