At The Land Gardeners we are firm believers in the benefits of green manures. They are plants which improve soil fertility (including adding nitrogen), improve soil structure with better drainage and water retention, suppress weeds and often attract beneficial insects and other predators.
For soil fertility – plants from the legume family fix absorb nitrogen from the air and fix it in the nodules. We often underplant a row of beans or sweat peas with crimson clover, digging it back into the soil as the plant decomposes eg
Sow clover and vetch in rows in your garden to fix nitrogen - Garden Organic suggest growing vetch under blackcurrant bushes in winter to fix nitrogen on their root nodules, then hoe off in spring
Sow white clover around the base of fruit trees to keep weeds at bay and provide good wildlife habitat
For improved soil structure – in heavy soils the expansive and often deep root system of green manures can open them up, allowing better drainage while in light soils the roots attach themselves to the light soil particles acting as a sponge and thus holding onto water and nutrients.
Weed suppression – The advantage of green manures is that they are often quick growing so we use them in areas which are not being cultivated as quick fill-ins or “catch crops”, to smother young weed seedlings and help feed the micoororganisms in the soil. Eg
Sow mustard which is quick to germinate and can be dug in 6 weeks after sowing. Do not allow it to go to seed so best to dig in when the first flowers show.
We also use rows of buckwheat – its white flowers are so pretty in the summer in the vegetable garden.
In the autumn try rows of grazing rye or winter vetch to keep the soil covered over winter and dig in in the spring – allow a month between digging the rye in and replanting as it releases a temporary substance which inhibits seed germination
Sow low growing green manure eg trefoil to keep ground covered between tall crops
Pest control – There are beautiful flowering green manures which attract bees and hoverflies – they also look wonderful in the garden! eg
Sow crimson clover for its beautiful red flowers and Phacelia tanacetifolia for a sea of lilac blue flowers – both heavenly for bees – you can grow these throughout the summer in rows or small gaps in your beds
We use a variety of green manures for different purposes in our cut flower and vegetable beds always digging them at their maturity but making sure they are not too leggy so they decompose quickly and feed the soil. We chop them up into clumps and leave the plants to decompose on the surface.
For a full list of Green Manures – what and when to plant see: - https://www.gardenorganic.org.uk/sites/www.gardenorganic.org.uk/files/Green Manures - list_1.pdf
We use liquid teas throughout the growing season as they contain important nutrients for plants – nitrogen, phosphorous and potassium.
We put a variety of greens - comfrey, nettles, weeds that have not seeded – in bags made from mutton cloth for a couple of weeks and soak them in buckets of rainwater. After approximately 4 weeks we add a cup full of the liquid into a watering can of collected rain water, then water the soil and spray onto leaves as a foliar feed.
Nettles are particularly high in nitrogen – and also good for providing magnesium and iron.
Comfrey is balanced in nitrogen, phosphorous and potassium – the latter being particularly good for flowers, seed and fruit. We plant Bocking 14 comfrey which is higher in nutrients than the common comfrey and less invasive in your garden.
We also use layers of compost in our compost windrow as a compost activator and spread it as a mulch around plants (particularly hungry feeders like dahlias) to both suppress weeds and feed the plants as it breaks down.
As well we use diluted liquid seaweed regularly on our plants, to feed both the soil and as a foliar feed.