Choosing Green Manure Seeds can seem very confusing but with a little time and using a few rules the options will become clearer.

The choice of seed 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.

Use the table below when Choosing Green Manure Seeds to help work out which one will be best for you.

Alfalfa Apr -Jul Legume 2-3 months or up to 1 year for overwintering Avoid acid or wet soils, likes dry soil best Excellent nitrogen fixer, deep rooting draw up sub-surface minerals & break up soil pans,can be turned in the autumn or left to overwinter. It is almost a complete natural fertiliser.
Birdsfoot Trefoil Mar - Aug Legume
3 months or up to 3 years for  overwintering
Copes with light dry soils, preferably not acid Low growing so suitable for intersowing between taller crops with open canopies like beans, peas, sweetcorn etc. Good at fixing nitrogen, and good at suppressing weeds.
Buckwheat May – Aug Polygonaceae* 2-3 months Tolerates poor soils but does not like heavy soils. Short term, quick growing summer variety which produces a dense canopy of foliage that smothers & out competes weeds.
Caliente Mustard March – Mid Oct Brassica 2-5 months Most Biofumigant properties (suppression of soil borne pests & diseases by the release of naturally occurring gases).
Crimson Clover Apr – Sep Legume 3-18 months Good loam or sandy soil Good choice for smothering weeds, fixing nitrogen from the air and is a fast growing bulky green manure.
Fenugreek Mar – Aug Legume 2-3 months Well drained but slightly heavy soils, will tolerate lighter ones if fairly moist Quick growing annual, produces lots of organic matter.
Field Beans Sep – Nov Legume Overwinter Most but especially heavy clay soils. It will not tolerate drought conditions. Particularly good on heavy soils as it’s roots penetrate & break up the soil. A nitrogen fixer.
Fodder Radish May – Aug Brassica 2-6 months, may overwinter All types Long tap roots penetrate deep into soil and draw up nutrients. Produces lots of foliage which helps improve soil structure/moisture holding capacity & fertility.
Forage Pea Sep – Nov Legume 3-6 months Most Good nitrogen fixer, nutrient leaching prevention overwinter.
Forage Rye Aug – Nov Poaceae* 3-6 months Excellent for clay soil but suits most types Excellent for overwintering, and covering soil.
General Mix May – Jul Legume / Brassica Mix 2-6 months Most Good all-rounder for all year.
Italian Ryegrass Mar – Oct Poaceae* 2-24 months Most 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 Mar – Jul Legume 2-4 months Light sandy acid soils Very long tap roots that help break up the soil, excellent nitrogen fixer.
Mustard Mar – Sep Brassica 1-2 months Most Large volumes of organic matter helps improve soil texture & water retention.
Phacelia Mar – Sep Hydrophyllaceae* 1-3 months, may overwinter Most, but particularly dry ones Quick growing,weed supressing foliage, lots of organic matter.
Red Clover Apr – Aug Legume 3-18 months Good loam or sandy soil Fast growing perennial excellent ntirogen fixer & bulky growth smothers weeds.
Spring Mix Mar – May Legume 2-4 months Most Good all-rounder for early sowing.
Sweet Clover Mar to May & Aug to Sep Legume Up to 2 years Most. Does well on hard compacted soils, waterlogged soils, drought resistant & tolerates poor soil Has a vigorous root system that draws up minerals & penetrate heavy soil. Produces lots of leafy foliage that adds good organic matter when dug into soil.
White Clover Mar – Aug Legume 6 months or 2-5 years Most especially silt loam & clay soils but can be tolerant of poor drainage Excellent long-term green manure, low growing variety that can be inter-sown in between soft fruit eg Blackcurrants, a living mulch.
Winter Mix Aug – Sep Poaceae* & legume 3-6 months Most Good all-rounder for overwintering, with good weed suppression and prevents nutrient leaching. The combination of the Westerwolds Ryegrass means any Nitrogen present and stored by the Winter Vetches will be released at a slower rate as the organic matter decomposes over the course of the season.
Winter Tares (Vetches) Mar – May or Jul – Sep for overwintering Legume 2-3 months Avoid acid or dry soils, Likes heavier soils Good nitrogen fixer, weed suppression, nutrient leaching prevention overwinter.


*Doesn’t affect crop rotation.