My Green manures are kept in a tin in the allotment shed and they are always sown insitu and currently I know I have two packs but I don't have a clue what ones are left. Note to self do Green Manure audit when next on the plot, or if possible and it finally stops raining every day get them in a bed!
Green manures are usually sown in late summer or autumn and mop up any nutrients, preventing them being washed away by winter rain. When dug in the following spring, they release these nutrients back into the soil. Winter grazing rye and winter tares are hardy green manures that will carry on growing all winter before being incorporated back into the soil in spring.
Green manures can also be used to cover bare patches of soil in the spaces between crops, or during intervals between one crop and the next. Fast-growing mustard sown before mid-September can be incorporated in October, for example, or the frosted remains left as mulch.
Summer-grown green manures such as buckwheat and fenugreek form dense foliage that will effectively suppress weeds.
Green manures belonging to the pea and bean family (legumes) have the additional capacity of storing (fixing) nitrogen from the air to their root nodules, but only in summer. Nitrogen is a valuable plant nutrient.
Other benefits of green manures include protection of the soil surface from compaction by rain and shelter for beneficial insects such as ground beetles.
How To Use Green Manures
- Sow seeds in rows, or broadcast them across the soil and rake into the surface
- Once the land is needed for cropping, chop the foliage down and leave it to wilt
- Dig the plants and foliage into the top 25cm (10in) of soil After digging in, the site should be left for two weeks or more before sowing or planting out as decaying green materials can hamper plant growth
Cultivar Selection
Alfalfa (Medicago sativa): This perennial legume can be dug in after two or three months or left for one to two years; sow in April to July; good for alkaline soils. Nitrogen fixing may only occur if the seed is inoculated with nitrogen fixing bacteria prior to sowing.
Alsike clover (Trifolium hybridum): This perennial legume can either be dug in after two or three months or left in for one or two years; good for wet, acid soils; sow in April to August.
Bitter blue lupin (Lupinus angustifolius): This perennial flowering legume suits light, sandy, acid soils; sow in March to June and leave for two or three months before digging in.
Buckwheat (Fagopyrum esculentum): This half hardy annual will only grow in spring and summer best sown in April to August, it can be left for two or three months after sowing; grows well on nutrient-poor soils.
Crimson clover (Trifolium incarnatum): This perennial legume is good for light soils; sow in March to August and leave in for two or three months up to flowering.
Essex red clover (Trifolium pratense): This hardy perennial legume overwinters well and can be left in for two or three months or for one or two years after sowing; good for loamy soils; sow March to August.
Fenugreek (Trigonella foenum-graecum): This annual legume will only grow in the spring and summer; it is unlikely to fix nitrogen in the UK.
Grazing rye (Secale cereale): This annual crop is good for soil structure and overwinters well; sow in August to November and dig in the following spring.
Mustard (Sinapis alba): This annual crop from the brassica family should not be followed by other brassicas, as it could encourage build-up of the disease clubroot; sow in March to September and leave for two or three months before digging in.
Phacelia (Phacelia tanacetifolia): Later sowings of this annual crop may overwinter in mild areas, but it is generally best sown in April to August and dug in after two or three months; its flowers are very pretty.
Trefoil (Medicago lupulina): This legume can be annual or biennial and overwinters well but needs light, dry alkaline soil; it can be dug in after two or three months or left for one or two years after sowing; sow in March to August.
Winter field bean (Vicia faba): This annual legume can be left for two or three months after sowing (up to flowering) and is good for heavy soils; sow in September to November.
Winter tares (Vicia sativa): This annual legume is hardy and overwinters well, even in heavy soils; sow either in March to August and leave for two or three months before digging in, or sow in July to September for overwintering.
Problems
A dense carpet of green makes a perfect environment for slugs and snails so control measures may be needed after green manuring.
Decaying green manures can suppress plant growth, so allow at least two weeks between incorporation and planting or sowing.
Club Root can be a problem with green manures in the cabbage family such as mustard.
New Green Manures for 2020 into 2021
Crimson Clover - A fast growing weed suppressant and great for beneficial insects, crimson clover is an excellent nitrogen 'fixer'. Ideally dig in just before it flowers. Works very well in exposed areas. Sow: March-August Dig in: March-September. Packet will cover approx 20sqm (24sq yards).
Lucerne (Alfalfa) - A deep rooting nitrogen fixer which will reach down and improve the sub-soil. If desired it can be left for a year or more before being dug in. Sow: April-July Dig in: April-August. Packet will cover approx 20sqm (24sq yards).
Mustard (White) - Perfect for soils lacking organic matter, it grows on most soil types and produces large amounts of green matter and fibre and will help structure and moisture retention. Helps hold valuable nutrients and is ready for digging-in in only 4 to 8 weeks from sowing. Sow: March-September Dig in: March-November. Packet will cover approx 20sqm (24sq yards).
Phacelia tanacetifolia - Winter hardy so can be over wintered. Ideal for adding humus content to impoverished soils. Sow: March-September Dig in: March-November. Packet will cover approx 20sqm (24sq yards).
Winter Rye - One of the very best over-wintering green manures. Soil structure is greatly improved through the abundance of fibrous roots produced and nutrient retention is improved in wet weather. Sow: February-March or August-November Dig in: February-December. Packet will cover approx 20sqm (24sq yards).
Mustard Caliente - Fast growing green manure that improves soil structure and fertility. Adds organic matter and nutrients, giving the soil optimum health by suppressing weeds, soil pest and diseases. Sow: March-July or September-October Dig in: February-December. Packet will cover approx 70sqm (84sq yards).
The incorporation of green plant tissue into the soil is an ancient practice known as ‘green manuring’. Green Manures are used to disrupt pest and disease life cycles, improve soil fertility and nutrient levels and suppress weeds.
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Sow Indoors
Sow / Plant Outdoors
Flowers / Harvest
I have two types of Green Manure from Mr Fothergills one is The Green Manure Autumn/ Winter Mix Seeds which is made up of:
15% Crimson Clover (Trifolium incarnatum)
20% Broad Leaf Clover (Trifolium pratense)
30% Westerwolths Rye Grass (Lolium multiflorum)
35% White Tilney Mustard (Sinapsis alba)
Clovers fix nitrogen in the soil. Rye grass and white mustard improve soil structure.
The other Green Manure from Mr Fothergill's is Mustard Caliente A fast growing green manure which has excellent soil improvement properties. Whilst it adds to the structure and fertility, it also adds organic matter, giving the soil optimum health. It will also suppress many weeds species, soil pests and diseases.
Sow Indoors 
Sow/Plant Outside 
Flowers/Harvest
