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.

VARIETY	SOW DATE	PLANT FAMILY	GROWING PERIOD	SOIL TYPE	BENEFITS
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.