Choosing the right green manure can seem very confusing but, with a little time and using a few rules, the options will become clearer. The choice will depend on why you are planting a green manure, how long you require the ground to be covered, what was there before and what you want to plant after, the time of year and the type of soil you have. You can then use the information below to help work out which of our green manures will be best for you.

Alfalfa Sow date: April to July. Growing period: 2 to 3 months or up to one year for overwintering. Soil type: avoid acid or wet soils; likes dry soil best. Benefits: excellent nitrogen fixer, deep rooting draw-up sub-surface minerals and break up soil pans; can be turned in the autumn or left to overwinter. It is almost a complete natural fertiliser.

Buckwheat Sow date: May to August. Growing period: 2 to 3 months. Soil type: tolerates poor soils but does not like heavy soils. Benefits: fast growing; germinates in 3 to 5 days, producing a dense canopy of foliage. Once dug in it rapidly decomposes. Thought to produce toxic substances that inhibit the growth of other seeds.

Caliente Mustard Sow date: March to mid-October. Growing period: 2 to 5 months. Soil type: most. Benefits: biofumigant properties (suppression of soil borne pests and diseases by the release of naturally occurring gases).

Crimson Clover Sow date: April to September. Growing period: 3 to 18 months. Soil type: Good loam or sandy soil. Benefits: good choice for smothering weeds, fixing nitrogen from the air and is a fast growing bulky green manure.

Fenugreek Sow date: March to August. Growing period: 2 to 3 months. Soil type: well drained but slightly heavy soils; will tolerate lighter ones if fairly moist. Benefits: quick growing annual; produces lots of organic matter.

Field Beans Sow date: September to November. Growing period: overwinter. Soil type: most but especially heavy clay soils. It will not tolerate drought conditions. Benefits: particularly good on heavy soils as its roots penetrate and break up the soil. A nitrogen fixer.

Fodder Radish Sow date: May to August. Growing period: 2 to 6 months; may overwinter. Soil type: all types. Benefits: long tap roots penetrate deep into soil and draw up nutrients. Produces lots of foliage which helps improve soil structure, moisture-holding capacity and fertility.

Forage Pea Sow date: September to November. Growing period: 3 to 6 months. Soil type: most. Benefits: good nitrogen fixer; nutrient leaching prevention overwinter.

Forage Rye Sow date: Aug to November. Growing period: 3 to 6 months. Soil type: excellent for clay soil but suits most types. Benefits: excellent for overwintering and covering soil. General Mix – Sow date: May to July. Growing period: 2 to 6 months. Soil type: most. Benefits: good all-rounder for all year.

Italian Ryegrass Sow date: March to April or August to September. Growing period: 2 months to two years. Soil type: most. Benefits: particularly good at lifting the nitrates in the soil and releasing them slowly. Easy to dig in after winter and fits into any bed in a crop rotation plan.

Lupins (Blue) Sow date: March to July. Growing period: 2 to 4 months. Soil type: light sandy acid soils. Benefits: very long tap roots that help break up the soil; excellent nitrogen fixer.

Mustard Sow date: March to September. Growing period: 1 to 2 months. Soil type: most. Benefits: large volumes of organic matter help improve soil texture and water retention.

Phacelia Sow date: March to September. Growing period: 1 to 3 months. may overwinter. Soil type: most, but particularly dry ones. Benefits: quick growing, weed suppressing foliage; lots of organic matter.

Red Clover Sow date: April to August. Growing period: 3 to 18 months. Soil type: good loam or sandy soil. Benefits: fast-growing perennial; excellent nitrogen fixer; bulky growth smothers weeds.

Spring Mix Sow date: March to May. Growing period: 2 to 4 months. Soil type: most. Benefits: good all-rounder for early sowing.

Sweet Clover Sow date: March to May and August to September. Growing period: Up to two years. Soil type: most. Does well on hard compacted and waterlogged soils; drought resistant and tolerates poor soil. Benefits: has a vigorous root system that draws up minerals and penetrates heavy soil. Produces lots of leafy foliage that adds good organic matter when dug into soil.

White Clover Sow date: March to August. Growing period: 6 months or two to five years. Soil type: most, especially silt loam and clay soils but can be tolerant of poor drainage. Benefits: excellent long-term green manure; low growing variety that can be intersown in between soft fruit, e.g. blackcurrants, a living mulch.

Winter Mix Sow date: August to September. Growing period: 3 to 6 months. Soil type: most. Benefits: Good all-rounder for overwintering, with good weed suppression and prevents nutrient leaching.

Winter Tares (Vetches) Sow date: March to May or July to September for overwintering. Growing period: 2 to 3 months. Soil type: avoid acid or dry soils; likes heavier soils. Benefits: good nitrogen fixer; weed suppression; nutrient leaching prevention overwinter.

Yellow Trefoil Sow date: March to August. Growing period: 3 months up to one year. Soil type: copes with light dry soils, preferably not acid. Benefits: low growing so suitable for intersowing between taller crops with open canopies like sweetcorn or beans. Good at fixing nitrogen and good at suppressing weeds.

This article appeared in Growing Green International magazine Num 31 (Summer 2013), p24. Information kindly provided by www.greenmanure.co.uk ©2013 Sow Seeds Ltd