Best Green Manures and Cover Crops for UK Winters
Ideally in a no-dig, organic, and productive vegetable garden, we wouldn’t need any cover crops because we are always sowing seeds and succession planting, meaning your beds are always full. Essentially your growing vegetables, these constantly acting as cover crops. However, nothing is perfect, not many of us have enough time or knowledge to do this type of succession planting. I for one, especially in winter find myself with bare beds on my allotment. If I’m not careful those beds will be covered in weeds before I know it and when you’ve taken on a plot that was as unloved and covered in perennial weeds such as horsetail and bindweed as I have I need every weapon in my organic arsenal to weaken those weeds and build healthy soil.
Cover crops are a great way of doing this, especially through winter when you have fewer crops growing in the ground.
What are Green Manures and what are cover crops?
Cover crops and green manures are quick-growing crops grown to protect the soil and continue adding nutrients to it while the soil would be otherwise bare. The difference is only in that some green manures are known for their health benefits to the soil. These are then dug into the soil to decompose whereas a cover crop would be removed.
Cover crops can be grown in summer time too if you have a bare bed to reduce the amount of weeds that will grow. Though weeds will not grow as vigorously in the winter, cover crops during the winter will still suppress weeds and help to build structure and feed the health of your soil.
Green manures are a purely planted-based solution to adding nutrients to the soil and are a popular choice for vegan (veganic) growers who do not that to use animal manures.
Do I need green manure or a cover crop on bare soil?
Adding a crop or green manure to cover the soil between crops or over the winter season is not the only way to cover it. You could also add a layer of compost, wood chip or animal manure to cover it, which will do the same thing of feeding the soil and weed suppression.
How will cover crops benefit my soil?
Improved soil structure and fertility: Many cover crops, especially ones with deep roots such as radishes and daikon improve the soil structure, increase the soils ability to withstand heavy rainfall and droughts and will improve fertility for future crops. This also makes your soil much more climate resilient at a time when it is very much needed.
Weed suppression: Having a cover crop will provide shade to the soil and reduce the germination of weeds. It will help to outcompete perennial weeds such as horse tail and bindweed.
Erosion control: Cover crops provide a protective layer on the soil’s surface preventing it from being eroded by wind and rain. A healthy soil structure and mulch will also do this which a cover crop is adding too.
Nitrogen Fixing: Some cover crops such as cloves, vetch and peas have a unique ability to fix atmospheric nitrogen in root nodules. This process adds nitrogen to the soil, reducing the need for synthetic fertilizers, and benefiting future crops.
Pest control: Certain cover crops can attract beneficial insects and pollinators, helping the biodiversity of your plot and the need to pesticides.
The Best Green Manures for UK Winters
As the winters in the UK are fairly mild but wet choosing the right green manure for our climate will ensure success.
Winter Rye (Secale Cereale): Hardy and cold-tolerant cereal grain. Provides excellent weed suppression and can be nitrogen-fixing. Sow in late summer or early autumn.
Field Beans (Vicia Faba): Cold tolerant, nitrogen-fixing, attracts beneficial insects. You can let them grow on to harvest as a crop for early spring during the hunger gap. The bean tops can be steamed or added to stews and the bean pods can be eaten raw or cooked. Sow in autumn.
Red Clover (Trifolium Pratense): Cold tolerant, nitrogen-fixing, attracts beneficial insects. Sow in later summer or early autumn.
Winter Tares (Vicia Sativa): Another cold-tolerant legume. Winter tares are good for weed suppression and soil improvement. Best sown in late summer or early autumn.
Mustard (Sinapis Alba): Fast-growing mustard acts as a biofumigant, suppressing nematodes and soil-borne diseases. Plant into late summer or early autumn.
Forage Radish (Raphanus Sativus Var. Oleiformis): These are edible and can be used in Asian cooking, though can mainly used as a cover crop. Plant in late summer or early autumn for winter harvesting.
Italian Ryegrass (Lolium Multiflorum): A fast-growing grass it is very efficient in suppressing weeds and is ideal for quick cover during winter. Ideally sown in late summer or early autumn.
Should I dig cover crops in?
I do not dig cover crops or green manures into the soil as a No Dig gardener because I do not want to damage the soil structure.
Green manures can be cut off at the root and added to the compost pile. Once broken down this can be added back to your garden beds as a mulch. Alternatively, let the frost kill them off and leave them to break down on the soil acting as a cover to the soil at the same time. Once you are ready to use plant into the bed, rake off dead leaves or add a mulch such as homemade compost or animal manure onto of the leaves and plant directly into this.
Not digging green manures into the soil not only means you are protecting the nutrients and life within the soil but also means you are in no rush. Many cover crops will need digging in before they flower so they are softer and easier to dig in. Not digging them in means you can leave them until you are ready to use the bed, letting them flower and benefiting the local insect population.
How to sow cover crops and green manures.
Most cover crops and green manures can be sown directly as they are hardy, fast growing crops. Simply weed and rake the soil. Scatter the seeds, rake over again and water. Large seeds such as field beans can be sown in rows.
