How to sow green manure in your garden

Green manures: free soil improvement

Leaving bare soil in your garden is a waste. Wind and rain wash away the topsoil, weeds move in and soil life declines. Green manures fix all of that. You sow them, they grow, and when you dig them in they feed the soil. It costs next to nothing and the results are remarkable.

GardenWorld helps you visualise a garden design suited to your soil type. Know your ground and you'll pick the best green manure too.

What does a green manure actually do?

Green manures are plants you sow to improve the soil, not to harvest. Their roots break open compacted ground and create channels for air and water. Above ground, the plants protect against erosion and suppress weeds. Some species, like clover and vetch, capture nitrogen from the air and store it in their roots. Free fertiliser, essentially.

Which type and when?

Spring and summer (March-August)

Phacelia: the all-rounder. Grows fast, flowers a gorgeous purple and attracts bees. Suitable for any soil type. Available as seed at garden centres.

Yellow mustard: a rapid ground cover that fills a bed in six weeks. Breaks up clay and smothers weeds. Don't sow before brassicas or radish, as they're related.

Clover: fixes nitrogen and makes a lovely ground cover. White clover works well under fruit trees.

Autumn (August-October)

Winter rye: grows right through winter and protects the soil from erosion. Its extensive root system improves soil structure enormously. The number one choice for heavy clay.

Vetch: a legume that fixes nitrogen. Combine with winter rye for the best result.

Fodder radish: breaks through compacted layers with its deep tap root. Ideal if your soil has a hard pan.

How to sow green manures

Loosen the surface lightly with a rake. Scatter seed evenly at the rate shown on the packet. Rake it in gently and water if it's dry. Within a week you'll see the first seedlings.

When to dig them in

Dig green manures in before they set seed, or you'll sow them unintentionally. Most types should be incorporated four to six weeks before you want to plant. Chop the plants with a hoe or spade and work them lightly into the top layer. Soil organisms do the rest.

For winter-hardy types like rye, wait until early spring. Chop them down and leave the material for a few weeks before incorporating.

Green manures in the ornamental garden

Green manures aren't just for the veg patch. Got a bare spot in a border? Sow phacelia and enjoy the purple while the soil improves. Or scatter clover among your perennials as living mulch. It looks tidy and your soil benefits.

Frequently asked questions

Can I sow green manures in pots? In large containers it's possible, but the benefit is limited. They work far better in open ground.

Do I need to fertilise when sowing a green manure? No, that's the whole point. The green manure adds nutrition itself.

How deep do I dig them in? Not too deep. The top 10 to 15 centimetres is enough. Deeper digging disrupts soil structure.

Small seed, big impact

Green manures are one of the cleverest tricks in gardening. They cost a few pounds, improve your soil and look good too. Plan your garden at GardenWorld and discover which patches of ground would benefit from a green manure.