Gardening for the Planet: Growing Green

In biodynamics, the soil is our most valuable asset. Everything possible is done to nurture and protect it to ensure it is in the best health so we, in turn, can grow strong, healthy, productive crops full of vitality and nutrition. Whether you have a small or large plot, one simple way to protect and improve your soil is to keep it covered, either with an edible or green manure crop.

What’s a green manure?
Green manures – also known as cover crops – are plants grown specifically to be dug back into the soil to improve it. Think of them as a living mulch and you’ll soon never be without them. Many, such as phacelia and crimson clover, have such beautiful flowers you’ll probably want to grow them anyway.

Green manures can be sown spring – autumn. Some as fast growers, bulk up quickly , and are intended as a quick cover crop; others are hardy, and can be left to overwinter and dug into the ground when convenient. As well as helping to bulk up the soil with extra precious organic matter, they:
• help keep soil structure intact and prevent erosion of nutrients
• suppress weeds, so less weeding
• when left to flower, attract and provide nectar for pollinators
• provide a habitat for predators such as slug eating frogs

Two types
Green manures can be categorised into legumes and non-legumes: Legumes include beans, peas, clover and lupins. They are easy to grow, are important nitrogen-fixing plants, and so are a natural way for gardeners to add nitrogen without chemical fertilisers.
Non-legumes include all the other green manures: grasses, buckwheat, phacelia and crucifers such as mustard. They add heaps of organic matter to the soil, help suppress weeds and are great at preventing nitrate leaching from bare soils.

Top Tips:

• Green manures are not made all equal! Different ones suit different soils and situations. To help you make the right choice, we’ve put together this handy chart which you can download here. ( Pdf)

• To ensure your green manure gets the best start, prepare the seed bed carefully as you would for any edible crop.

• Never sow a green manure before or after a vegetable crop from the same botanical family – the green manure could act a bridge to spread disease. For example, growing mustard, which belongs to the brassica family, before another brassica crop – eg cabbages/kale/ broccoli/ Chinese vegetables – increases the risk of clubroot, a soil-borne disease.

• If you cut a green manure before it flowers, it will usually re-grow ― leave the cut foliage in situ to act as a mulch whilst it decomposes. This is perfect if you have inherited a previously overworked patch, as you’ll feed the soil helping to put it in great shape for the following season.

• Always cut green manures before they have the chance to set seed. Many are prolific self-seeders and can become an unwelcome guest! To dig them in, use a sharp spade and turn the plants back into the soil, chopping any tough clumps as you go. In heavy soils, aim to bury plants no more than 15cm deep and 18cm in light soils.

• Follow a ‘no-dig’ strategy? Cut the manure just above the soil after flowering and transplant edible crops through the severed tops, leaving the cut tops and stubs as a surface mulch or loosen the soil and pull the plants out by the roots, layering them on a bed as mulch.

Where to buy:
Green manures are becoming very popular. Tamar organic seeds have one of the best selections.

Photos: Lee Parish.