Cover crops are plants used to maintain and improve the soil quality of gardens and fields. They are one of the finest ways that nature itself can be used to improve soil quality. Cover crops are perfect for gardens where you want to avoid chemicals because the crops do everything naturally themselves! But what exactly are cover crops, what do they do, which should you plant, and how can you implement them yourself? Keep reading to find out more about the amazing benefits of cover crops for gardens.
What Are Cover Crops for Gardens (versus Fields)?
As far as a cover crops definition goes, cover crops – also known as ‘green manures’ – are plants that are used for their beneficial effect on the garden or field they grow in, rather than any desire for the cover crop plant itself. Some of the most popular cover crops for gardens are:
- Lupin (Lupinus angustifolius)
- Broad beans (Vicia faba)
- Buckwheat (Fagopyrum esculentum)
- Crimson clover (Trifolium incarnatum)
- Marigolds (Tagetes patula)
- Mustard (Brassica alba)
- Phacelia (Phacelia tanacetifolia)
- Soybeans (Glycine max)
Constrast this with cover crops for fields. When wishing to enrich an entire field, you might not want to plant marigolds. Instead, you’ll be looking at a more effective cover crop that will blanket the field and be useful for harvest later on.
But why are the above garden cover crops useful? What do they actually do as cover crops and why are they beneficial?
Which Cover Crops to Plant and Why
Many of the benefits cover crops bring to a garden are universal. They bring the general addition of biomass to the soil and they create habitats in which beneficial microbes and arthropods can live. However, some of the most important benefits of cover crops are particular to the plant itself. Here are explanations of why the above cover crops are so beneficial in a garden.
Lupin grows very quickly, so it adds a very large amount of organic matter to the soil. It also breaks down rapidly when the plant dies. As a result, it can be dug directly into the soil without prior composting. The roots of the lupin play host to soil bacteria that capture nitrogen from the air and then infuse it into the soul. This is important, as nitrogen is one of the most important nutrients for a plant, yet most plants are not able to source it from the air by themselves. In this sense, lupins enrich the soil by pulling nitrogen out of the air and making it accessible to surrounding plants.
Similar to the lupin, the broad bean produces a large amount of organic matter and plays host to bacteria that fetch nitrogen from the air. Broad beans’ advantage over lupins, however, is that they can be grown successfully in colder climates or seasons. They also do well without a lot of sun, so if you’re looking for cover crops that do well in shade, broad beans are a great option.
Buckwheat grows very quickly and is quite tolerant of drought. Its true specialty, however, is that it attracts an enormous number of beneficial insects. Buckwheat plants flower prolifically for a long period, with small white flowers that provide a steady source of nectar. Desirable garden insects, such as the ladybug (or ladybird, if you’re from the UK like me!), eat a huge number of species we humans consider to be pests but fall back on nectar as a steadier source of nourishment when their prey numbers are low. Providing a significant source of nectar encourages a very useful local population of hunters in your garden.
Crimson clover combines the benefits of all three of the above to some extent: it fixes nitrogen, grows a large quantity of biomass, survives the winter in dormancy, and provides nectar for beneficial insects. Clover is a very good general-purpose cover crop. Crimson clover also makes a good cover crop because it can be used by itself or in rotation with vegetables.
As a cover crop, marigolds are popular because they are so pretty, but they also have quite a special trick up their sleeves (stems?). Marigolds and are not at all like other cover crops. The roots of marigold plants exude the chemical ozone, which causes nematodes (a type of soil microbe) to mature but never reproduce. In turn, this decimates their population. All this said, marigolds are best used after some careful research because dropping a nematode bomb is not always beneficial to the soil…
Mustard cover crops are another very interesting cover crop. The crops produce a large number of ‘glucosinolate’ chemicals. When you cut down a mustard crop, the glucosinolates leak into the soil and poison a wide range of unwanted soil organisms. Like marigold, mustard cover crops should be used after some research because the glucosinolates will potentially kill desirable soil organisms as well as the undesirables.
Phacelia is what beneficial insects dream about – it’s a beneficial insect wonderland. This wonderful cover crop attracts an incredible range of bees, ladybirds, hoverflies, and other killers of pest species. Once phacelia’s purple flowers begin to open, the entire patch buzzes and waves about as various insects land and take off. In addition to looking beautiful, it’s fascinating to hear the buzz of activity there!
Soybeans are nitrogen-fixing experts. An acre of soybean can fix an amazing 60 kilograms of nitrogen during their partial year of growth! Soybeans also produce an unusually high quantity of organic matter to improve the soil, so again they make an excellent cover crop for gardens.
It should be clear by now that the species of cover crop used can have a huge impact on the effect in the garden. Make sure you do your homework before you plant!
How to Implement a Successful Cover Crop for Your Own Gardens
- Work out what you want from your cover crop. Are you creating a haven for beneficial life? Wiping out nematodes? Adding organic matter to depleted soil? The seeds you sow must depend on what your garden needs.
- Buy your seeds. Make sure to buy from a reputable vendor, as it is not unheard of for people to buy seeds that aren’t exactly as advertised. Poor quality seeds also have lower germination rates (remember this for profitable herb growing, too!)
- Prepare the area of the garden to be planted. Preparation basically consists of digging at the soil to severely damage existing weeds, exposing soil for your seeds to grow in, and loosening the soil up for the future roots of your cover crop.
- Scatter seeds thickly in general, but check species-specific sowing instructions on seed packets in case they need more space. Remember that for a cover crop, you are not interested in the health and vitality of any individual plant: you just want a lot of plants in general, so make sure you plant densely. Dense planting also helps the cover crop to suppress any weeds attempting to grow alongside them (although those weeds might be beneficial in and of themselves, so check out this article before you get rid of them!).
- That’s it! Wait, water, and watch! Remember to check for any specific instructions about long-term cover crop care, but most can be left to get on with it. Too much interference from humans interrupts their growth and can affect how well they work, so less in more with cover crop care.
Will You Use Cover Crops?
Cover crops can do a lot for your garden, and they can be a pleasure to maintain! Any sized patch of land is a viable candidate, from an entire field to a currently empty plant pot. What’s key is to make sure to select your cover crop species based on your needs, and then get the seeds from a trusted source. Give your newly planted cover crop a little extra love to begin with. Water it and weed it, and then just let it be. Your garden will love you for it!