Have you questioned using fertilizer and chemicals to keep your soil and plants perfect from season to season?
You’ve probably noticed the many synthetic sprays, amendments, and applications out there to help your garden thrive. Sure, they save you a lot of time in some ways – but think about where all those chemicals go.
Want to grow your garden in a smarter, more aware way? What about with techniques that are better for the environment and the soil food web, and which help to keep all those chemicals from flushing down into local water supplies?
Then consider cover cropping! It’s a nature-friendly, rewarding way of providing your plants with fertilizer, good nutrition, disease management, and protection between plantings.
In the infamous plant nutrient book “Teaming with Nutrients” by Jeff Lowenfels, available on Amazon, this seasoned soil scientist calls attention to the very real truths about synthetic fertilizers these days.
Every summer, pounds upon pounds of synthetic nitrates and phosphate create runoff in our rivers and streams, traveling down the Mississippi River and causing dead zones in the Gulf of Mexico.
It would be easy to blame conventional farmers – but did you know that, according to Lowenfels, the average gardener tends to use three times more synthetic fertilizer per acre than the average farmer?
As such, you can make a real difference as a gardener by choosing cover cropping, for a happier garden and ecosystem.
As a nice extra, many cover crop plants also save you time and help to cut down on the tough work with erosion control, soil management, weeding, and much else besides.
Yes, that’s right – it’s not only gentle on your local environment and the planet overall, but on your body as well!
Many organic and sustainable farmers incorporate cover crops in small, medium, and even large crop operations. With increasing ecological concerns about the impact of herbicides, pesticides, and chemical fertilizers, conventional farmers are beginning to adopt these techniques, too.
Throughout this article, you will learn about cover crops and what you can do for your yard, garden, and local environment – not to mention you’ll be able to keep your garden-sourced meals clean and chemical-free!
The main reason to choose cover cropping is because it allows you to manage your garden in a safer, healthier way that saves you a surprising amount of sweat! According to this 2015 cover crop analysis survey, adding these methods and plants to your gardening routine could also boost your garden’s yields.
What is cover cropping?
If you’ve never heard of it, cover cropping plays a dynamic role in crop rotation. Certain beneficial seeds are planted in between your garden vegetable sowings, typically between harvest and the next planting.
These seeds then grow into temporary plants, which provide nutrients for your vegetables and the soil they grow in. They also perform other tasks during the season.
For example, the original term cover crop refers to seeded plants that act as placeholders in empty beds post-harvest, since they completely cover the bed.
Before heading into winter these crops die back, forming natural green manure (plant matter acting as fertilizer) and mulch that protects and covers beds from erosion – while organically nourishing the soil. But really, cover crops can do a whole lot more than just these two things.
So what are all the benefits they bring to your garden? Let’s take a look! I’m certain you’ll be convinced to give cover cropping a try.
As I first outlined, cover crops are clever end-of-season placeholders for your garden heading into winter.
Instead of buying or coming up with mulch materials, you can have cover crops do the covering for you instead – forming a layer of living mulch once cover plants die back from frost and cold.
Why is winter cover important? First of all, it prevents erosion and loss of fertile topsoil due to rain, wind, or snow. Weather and elements can (and will) strip away all the hard work you dedicated to soil building over the season.
A layer of soil cover also helps retain moisture, which is useful if you don’t want to watch your soil beds crack and dry up over winter. Retaining moisture is quite an important aspect of soil biology, while ensuring that the microbes living there are thriving and producing nutrients that are beneficial to your plants.
Come spring, winter cover crops minimize the amount of weeds that pop up, and which can crowd out your early seedlings. Certain winter cover crops also add the extra benefit of scavenging stray nutrients for your plants the following spring – which we’ll look at next.
Providing and fixing needed nutrients
That’s right – implementing specific crops between your vegetable plantings actually helps to create nutrients, and brings them straight to where they’re needed.
You can choose from many different cover crop seeds to re-mineralize and enrich your soil at any time of year – whether that be spring, summer, fall, or even going into winter, as was pointed out before. Some cover crops are tough enough to create and retain nutrients all through the winter, helping prepare your soil for hungry seedlings come spring.
You can propagate other in short windows between important plantings, even in the midst of a frantic gardening season – right at those times when your plants need a quick, extra boost in a pinch.
Why choose these over liquid fertilizers and synthetic applications?
Utilizing more natural, less invasive ways of bringing plant food to your soil helps support the soil microbiome in your garden beds.
Chemicals can artificially alter the natural composition of fungi, bacteria, and microbes – throwing off the delicate web of life that provides the very best natural nutrients for your plants.
Runoff of these chemicals creates dire consequences elsewhere: such as streams, lakes, oceans, their wildlife, and yes, our very own water tables and drinking water, too.
In short: cover cropping takes care of your soil, and the environment.
Over the long term, tending soil with cover crops grows you the tastiest and happiest plants, too – and quite possibly a lot more of them.
Balancing soil nutrients
Just as some cover crops bring in nutrients where they’re needed, others help tame and moderate soils that build up excess amounts. Yes, sometimes too many nutrients can be just as much harm to your plant as a lack of those same nutrients.
This usually happens with nitrogen, an important plant food element that can build up quickly.
Excess nitrogen can make soil too acidic, while garden beds high in trace minerals and potassium can be too alkaline for plant health – though it doesn’t always work this way.
Further, according to Jeff Lowenfels and Wayne Lewis in their landmark soil-science publication “Teaming with Microbes,” reviewed here, use of chemical fertilizers can create a buildup of nitrates in the soil.
These less natural (to plants) forms of nitrogen actually outcompete and make the more bioavailable, natural forms (which are better for plants) much harder to access.
Later on in the article, we’ll take a look at specific cover crops that curb nitrogen levels, as well as some other nutrients.
Improving soil structure
Also called “conditioning” the soil, cover crops contribute to better soil structure in a couple of ways.
First: using cover crops as green manure (letting them die back, then tilling them in) adds in organic matter, and supports what is called “soil aggregation.”
Soil aggregates are minute particles that give good texture to soil composition, improving its ability to retain and drain off moisture.
Another way of improving structure: cover crops help break up hard clay soils or “hard pan.” This is the thick crust of earth over deeper, finer layers of soil in a newly ploughed bed – one that needs more work and management to be usable.
Certain cover crop plant roots help break up and aerate these tough soils, making them lighter, easier to manage, and ultimately fostering a healthier environment for your vegetables to grow.
Biofumigation and preventing pests
Last but certainly not least, cover crops are not just helpful amendments and nutrients for soil food and structure – some have the ability to prevent and destroy a great deal of common diseases and weeds. Think about that the next time you’re spraying your garden for weeds and pests!
Certain species of cover crop, when died back and worked into the soil, release natural phytochemicals that suppress soil diseases: such as those caused by nematodes, among others. This is a technique called “biofumigation.”
Further, other varieties of cover crop help decrease weed numbers by outcompeting them before they even germinate. Some seeds and plants are designed to grow close together and cast shade, thus crowding out the invasive weeds that can put pressure on your preferred, but less rigorous plants.
Of course, you’ll have to be cautious with your cover crop techniques to make sure they don’t turn into pesky weeds themselves! If you’re not careful, it can happen.
Best cover crops
Cover crops can achieve many things for your garden, as you can see.
If their many benefits haven’t convinced you to do away with sprays and chemicals forever, then maybe a look at some of the best cover crops – and how to incorporate them into your garden plan – will do the trick.
The legume family of plants (also called Fabaceae) comprise a wide array of vegetables and foods: including all beans, peas, clovers, and many common species of herbs, trees, and shrubs.
The miraculous thing about many of these plants? As they evolved, many of them learned how to “fix” nitrogen – a major plant food requirement.
To give them an advantageous edge against other plants, legumes figured out how to extract nitrogen from the atmosphere and produce their very own food in less fertile areas.
Most legumes form a symbiotic relationship with certain bacteria (Rhizobium and Bradyrhizobium genera bacteria) that actually synthesize nitrogen straightaway, right in the plant’s roots.
When these cover crop plants die back, both the nitrogenous bacteria and nitrogen are released – making it freely available for the next crop to consume!
Do keep in mind: in some cases, nitrogen fixing doesn’t happen quickly or automatically with legume plants, since the bacteria isn’t guaranteed to be found in your soils.
In fact, with quite a few types of seed you buy, it’s wise to also buy “inoculant” containing rhizobia bacteria strains if you’re just starting out – you soak your seed in this inoculant, so it is guaranteed that your crop will find plenty of bacteria to complete the nitrogen fixing process quickly and successfully!
As such, this category of cover crop is ideal for providing nutrition to soils that lack it, specifically those that are barren or imbalanced. It also supports bacteria that help naturally create the form of nitrogen plants need, rather than suppressing it through chemical changes in the soil from fertilizers.
Legumes also fit well in rotations after a light-feeding plant, and before a heavy-feeding one. According to the Sustainable Agriculture and Education website, nitrogen-fixing cover crops may not do too well following a crop that has heavy nutrient requirements (i.e. corn, tomatoes, or kale).
Not all legumes make good cover crops, mind you. But after many centuries, even millennia of observation and use, the following leguminous plants have become decidedly unanimous choices for good nitrogen-fixing crop rotation.
A very prominent cover and rotation crop over the ages, this legume (Medicago sativa) achieves an incredibly deep and remedial effect on your fields and beds.
To really see its benefits, however, it’s a cover crop you’ll have to let grow and nourish your beds for a few growing seasons – for at least two years, according to farming experts at Cornell University.
What are alfalfa’s benefits as a cover crop?
- Nitrogen fixing – Like its other legume relatives, alfalfa’s roots contain bacteria that produce nitrogen for the plant by pulling it from the atmosphere. Crops planted afterward show better health and growth.
- Controls phosphorus, magnesium, and potassium – While alfalfa does fix atmospheric nitrogen into soil, it soaks up a lot of other nutrients as well. As such, it may be better to plant as a cover crop to balance soil nutrients.
- Improves soil structure – It sets out shallow surface roots, while sending down one long taproot into deeper soil layers. After being tilled in or removed, hard soil structures are broken up and loosened.
- Suppresses weeds – Alfalfa will establish thickly enough to crowd out other germinating weeds. But take care that alfalfa doesn’t spread and become a weed itself.
- Controls erosion, provides winter cover – In winter, alfalfa dies back as a perennial to re-emerge in spring. It’s foliage thus provides cover and protects against runoff.
Field peas (Pisum sativum) don’t have to be kept in the ground for as long as alfalfa to fix some nitrogen in beds that need it. Compared to what alfalfa can do, however, you could call their nitrogen contributions modest at best.
For a quick cover crop, field peas make for your best springtime choice. You can plant them with rye or oats (other types of cover crops) for support and structure, as they create natural trellises for peas.
In late summer or fall, they are a very popular crop to plant with oats in particular – while oats support the peas, the peas provide nitrogen in return. In the fall, the oats are consequently killed by frost to provide winter ground cover.
- Nitrogen fixing – Like all other legumes, field peas fix nitrogen.
- Winter cover – Peas provide modest ground cover – when planted symbiotically with oats, they create a thicker winter ground cover.
A robust choice, red clover (Trifolium pretense) might not fix as much nitrogen as alfalfa – but it will provide more than field peas. It can be a better choice than field peas too for wetter, shadier areas, and cooler temperatures when need be.
It works well when sown with a thicker planting of tall cover crops that cast shade (like most grains and grasses). However, be careful not to select it for beds already high in nitrogen – it fixes large amounts no matter what!
Like field peas, it’s better to plant red clover during cooler times of year, like spring and fall. Unlike field peas, it is a short-lived perennial – peas don’t return once they’ve died back, but red clover will return in spring.
Since it spreads thickly, it can be great for suppressing weeds as a ground cover. Take care that red clover doesn’t become a weed itself, by removing its flowers in May and September!
- Nitrogen fixing – Like its legume relatives, red clover fixes nitrogen (and quite a lot of it).
- Improves soil structure – Shallow and long taproots help to break up hard pan and thick, compacted clay soils.
- Suppresses weeds – A lush, creeping growth pattern will outcompete and stifle out weed seeds and sprouts.
- Controls erosion, provides winter cover – The plant’s matted growth and roots retain topsoil, also preventing soil loss over winter.
Vetches – but especially hairy vetch (Vicia villosa) – are up at the top of the list of nitrogen fixers, right next to alfalfa. This makes it a popular addition to crop rotation in both conventional and organic farming.
It’s winter hardy, so you can plant it in late summer or fall with high hopes to see it again in spring. But you must give it all of the following spring (until the end of May) to do its work, since vetch fixes the most nitrogen in May.
Afterward, it must be completely pulled out, cut back, or mowed to prevent flowering and spreading. If not controlled, vetch quickly becomes an invasive weed and a big problem!
Avoid planting other legumes and grains right after cover cropping with vetch, as it can increase the chance of root rot, nematodes, and white mold in those plants, according to Cornell University. Vetch also does additional favors for soil by preventing weed growth, and improving soil structure.
- Nitrogen fixing – An excellent nitrogen fixer, creating almost as much nitrogen as alfalfa.
- Controls phosphorus and potassium – While adding lots of nitrogen, vetch demands a lot of phosphorus and potassium. As such, it can help balance soil – though it may need extra helpings of these other two minerals to thrive.
- Improves soil structure – Helps condition the soil into a finer, healthier texture with better soil aggregates.
- Suppresses weeds – It grows thick enough to crowd out the weeds you worry about, but be sure to control vetch by removing it before flowering in May.
- Controls erosion, provides winter cover – Since it survives through winter, it provides a layer of natural mulch and protection for your soil beds.
Grasses and grains
Throughout history, growers not only figured out that grains were delicious when grown, processed, and eaten, they also discovered that they served certain uses for the soil and other important crops when grown in specific ways.
Some grains are fixers of other nutrients (besides nitrogen) that are important to grow healthy vegetables and plants.
They don’t fix nitrogen at all, unfortunately – but they can and do assist legume nitrogen fixers, and achieve some of the same tasks that legumes accomplish.
Let’s take a look at the best of them!
These are a thick, pervasive genus of grasses (Lolium) that can do a lot as a cover crop. They prevent compaction, loosen up soils, provide a natural winter mulch, control nitrogen, suppress weeds, and help reduce erosion in desired areas.
They enjoy warm weather most of all, and dislike the excessive hot temperatures of midsummer – making them ideal to seed in spring and early summer.
- Controls nitrogen – In soil areas with excessive nitrogen, you can plant annual ryegrass to keep levels down, while balancing the soil ecology with other nutrients. They will leave enough nitrogen for use by future crops.
- Improves soil structure – The fibrous root systems of ryegrasses break up hard pan into siltier, finer soils that are easier to work with – for both you and your plants.
- Suppresses weeds – These grasses grow thick to crowd out weeds in both fall and spring, in time for their removal and planting of new crops.
- Controls erosion, provides winter cover – Year round, ryegrass’s above-ground parts – whether live or dead– provide soil protection from the elements, allowing beds to rest without losing vital nutrients.
Buckwheat (Fagopyrum esculentum) provides wheat-like seeds that may be cooked and used as a grain. In the world of cover cropping, this stout relative of rhubarb has a very special place: it’s a quick-growing plant that fixes nutrients in a short amount of time, a task no other crop can do.
It’s a lover of warmth, however, so you can only plant it from late spring to late fall. It wilts in excessive heat and dryness too, so be careful using it in dry climates or during hot, droughty periods.
On the plus side, it takes only a month and a half to do its job, so you can fit it in between tight plantings – and you can also plant it successfully in barren soil.
Once buckwheat flowers, it’s time to cut it back to retain those fixed nutrients. This crop uses up a great deal of the nutrients it scavenges, just to produce flowers and seeds.
If you time it well, you can plant buckwheat a month before the suspected frost date. Frost and cold temperatures kill the plant, and the leftover foliage creates very light natural mulch and nutrient green manure for next spring.
- Fixes calcium and phosphorus – Buckwheat root systems know how to find, produce, and maintain both of these minerals. Once the plant is removed, these nutrients left behind are available for other plants.
- Suppresses weeds – This grain grows aggressively, and quickly. When alive and seeded thickly, it prevents growth of other weeds. When died back in winter, its dead growth further suppresses weeds come spring.
- Improves soil structure and aggregates – Delicate roots leave the topsoil fine, fertile, and ready for fresh planting after removal.
While it achieves comparatively less than other crops, oats (Avena sativa) nevertheless have a very popular function and place in cover cropping. A lover of cool temperatures, oats are planted in either the spring or the fall, for different reasons.
In the spring, it is tilled back into beds to provide nutrients and green manure for upcoming plantings. In the fall, it is eventually killed off by frost and makes a thick winter cover, as well as spring fertilizer.
The greatest asset of oats is that they grow rapidly, and can be killed and removed easily afterwards. Oats are often planted with peas and rye to help out-compete weeds that can threaten them.
- Green manure – Oats turned back into the soil provide nutrition for the next plantings to come.
- Suppresses weeds – This crop sprouts quickly and grows thickly to out-compete unwanted weeds, especially for other cover crops.
- Controls erosion, provides winter cover – Oats die back when faced with cold temperatures, and their dead growth protects the soil from erosion.
It’s not just a delicious grain found in pumpernickel or rye breads. Rye (Secale cereale) is also an excellent cover-cropping grass, for many reasons!
It helps support nitrogen-fixing legumes (most commonly field peas) with its intricate root system, preventing the loss of nitrogen to deeper soils even when it cannot fix it on its own. When both alive or died back, this tall grass prevents weeds and provides excellent winter cover.
- Maintains nitrogen – It cannot fix nitrogen, but its roots prevent nitrogen from leaching (sinking deeper), which makes it inaccessible to crops with shallow roots. This means it’s a great companion for nitrogen fixing plants, to help ensure that beds soak up as much nitrogen as possible!
- Suppresses weeds – Tall growth prevents and overshadows any competing weeds.
- Controls erosion, provides winter cover – It’s a cold-tolerant grass, making it a fantastic choice for fall planting into winter. Its growth (and died back growth, too) cover beds to let them rest, while preventing runoff.
Sorghums are a genus of grain grasses, including sorghum sudangrass (Sorghum bicolor) and sudangrass (Sorghum bicolor var. drummondii). They are tall, almost corn-like plants that suppress weeds, provide cover, give green manure to the soil, and help biofumigate against certain diseases.
What’s more, they’re lovers of hot, dry weather, need very little care, and their job is complete after a couple months. They’re not incredibly common as a grain cover crop, but all the same, they can leave behind amazing benefits.
A bonus: they’re tall and stalky, making excellent natural trellises for vining plants like peas, melons, cucumbers, and squashes.
- Green manure – Cutting the above-ground stalks reinvigorates root growth. When both stalks and roots are churned into soil, it boosts available nutrients for the next plants.
- Biofumigator – Not only does tilled-in plant matter provide nutrition, roots and stalks are known to discourage certain soil diseases and problems such as nematodes.
- Suppresses weeds – Tall growth casts shadows and prevents seeds from germinating – working even better when densely grown.
- Controls erosion, provides winter cover – Died-back growth before winter can work as a mulch for the cold months, and leftover roots in the ground discourage runoff of topsoil.
A prominent grain of eastern Africa, teff (Eragrostis tef) is a lover of warm and hot temperatures, like buckwheat and sorghum. More than either grain, teff can withstand very dry, rain-deficient weather – while growing thick enough to suppress weeds.
It needs little to practically no management too, while its roots help improve the texture and makeup of the soil.
- Suppresses weeds – As a grain, teff grows thick, which crowds out weeds and reduces competition.
- Improves soil structure and aggregates – When removed, it leaves the soil with a crumblier, finer texture than before. For that reason, it could help condition moderately tough soils – but not hard pan.
“Brassica” is a collective name for plants of the Brassicaceae or Cruciferae family, many of which are commonly grown vegetables. Some common brassicas you’ve probably heard of: broccoli, radishes, kale, and cabbage.
Not only do some species make for great food crops, some of them have cover crop capabilities as well. They are amazing biofumigators above all else, releasing chemicals when they die that prevent and suppress soil-borne diseases which could afflict other plants.
They also add great aeration to the soil, improve soil structure, and help with weed suppression and winter cover, too.
Also called salad rocket, arugula (Eruca sativa) is a favorite salad green for its tangy, spicy, and meaty leaves. Planted in late summer or fall, it covers beds for winter, though it is mostly used as a biofumigator.
Tillage farmers with large machinery use brassica relatives called rape (Brassica napus) and forage turnips (Brassica rapa) for these same purposes. But these are much harder to remove and use this way without larger tillers and farming machinery.
With the right garden equipment, arugula is a good choice for the backyard or small space gardener – and you can even harvest the leaves straight from your cover crop for kitchen use!
- Suppresses weeds – Upon dying back, arugula creates thick cover that hampers weeds from germinating or thriving.
- Biofumigator – Plant matter, when destroyed and decomposed, produces glucosinolates – compounds that suppress nematodes. (Side note: arugula could be a great garden food cover crop alternative to yellow mustard, usually planted before conventional farm tomato crops to stifle nematodes – one of the tomato’s worst foes.)
- Improves soil structure and aggregates – Shallow root systems leave the topsoil finer, crumblier, and more ideal for plants to follow.
- Winter cover – Creates a moderate mulch for beds in winter, though not as well as other brassica relatives rape and turnip.
Some cultivars of radish (Raphanus sativus) make a pleasing combination cover crop. They also provide great food straight from your garden – two functions rolled into one!
In my own experience, the daikon variety of radishes are the best to choose for cover cropping, though you can find other cultivars that achieve similar tasks. Their prized virtue is their long taproot, which helps to break up especially large, tough, clay beds.
If you want a crop to break up some difficult hard pan or a fresh bed, then you’ve found a friend in radishes. They also help quite a bit in the realms of biofumigation and weed suppression, much like their relative arugula.
When you’re done with the crop at the end of the season, however, you will have a cash of enormous, long radishes to pull up if you decide not to let them frost-kill over winter or till them in. Can’t argue with that!
- Aerate soils, improve structure – Cover crop radishes with lengthy roots create large air pockets once removed, transforming thick clay soil into a finer substance to work with over the course of a season.
- Suppresses weeds – Above-ground foliage provides enough shade to discourage many weeds, if planted densely enough.
- Biofumigator – If turned in or left to be cold-killed in the soil (not picking them before frost), they’ll emit the same compounds as arugula to stifle diseases and nematodes.
- Controls erosion, provides winter cover – The thick foliage of the live radish tops, while they are still growing in the ground, will provide a thick layer of mulch that lets your garden beds rest in winter while and preventing erosion – even after they frost-kill and die with root still in the ground.
There is an amazing selection of cover crops out there to choose from. Each offers some very useful additions for your garden rotation and soil beds, along with some remedial effects that would require a lot more effort otherwise.
Not only do cover crops serve your backyard needs, they are a much gentler choice for the natural biology of your soil – as well as the environment. Using these special plants can save you money, work, and a lot of maintenance on your soil to keep it naturally healthy and nourishing for your plants.
Which cover crop do you think would be right for your garden? Which plant will suit your needs for the next vegetable, food crop, or perennial to come into your yard and garden beds next?
Even better: what are your personal experiences with cover crops in your garden? Talk to us! Feel free to comment below. Happy spring gardening!
Photo Credits: Shutterstock.
About Adrian White
Adrian White is a certified herbalist, organic farmer, and health/food writer and expert. She aims to bridge the world of natural, holistic health and nutrition to the realm of organic foods, herbalism, gardening, and sustainability - or "Food as Medicine" - throughout her writing.