Green manure

What is green manure?

Green manuring means growing plants to feed the soil, writes Bob Sherman.

First plants are sown on open ground. When they’ve grown, they're dug in to the soil - where they release their nutrients as they decompose.

You can use different green manures depending on the time of year and what plants will follow.

Advantages

Green manuring is cheap and easy.

It protects the soil from heavy rain, stopping nutrients being washed away.

And it provides shelter for beetles and other useful creatures that feed on pests.

September to October is the perfect time to sow one of the best green manures, Hungarian grazing rye (pictured). You can buy seed from The Organic Gardening Catalogue

Hungarian grazing rye stops nitrogen being washed out of the soil over winter. Nitrogen is essential for leafy growth.

The rye will grow to 30-45cm by March, at which point you chop it down and dig it in.

It is ideal before planting potatoes, courgettes and squashes, or anything planted out in May and June.

But don’t use where you plan to sow carrots, beetroot or any other small-seeded crops you are likely to sow in March or April. This is because it will inhibit germination.

How to grow green manure 

  1. Fork soil to a depth of 15cm or so. Rake the soil level.
  2. Measure out roughly how much seed you need and divide it in half. Scatter half the seed working up the plot; then work across the plot using the other half. This gets an even spread.
  3. Rake the seed in and water the ground thoroughly if it is dry.
  4. Cover the seed in netting or twiggy branches to keep off the birds and cats. Remove this once seed leaves appear.
  5. When ready to dig in, rake off any bulky leaves for composting before digging in the roots.

Other good green manures

For spring planting:

Mustard Will keep the soil covered before a late planting such as courgettes; fast growing.

Trefoil Will build soil fertility where you are not ready to plant. Will last through the winter and re-seed itself.

For spring/summer planting:

Fenugreek Use in similar way to mustard (above).

Phacelia If you leave it to flower it becomes a bit tough and breaks down slowly. But the blue flowers are beautiful and bees love it.

Seeds and more information from The Organic Gardening Catalogue

Bob Sherman is Chief Horticultural Officer at Garden Organic