Replenish Your Soil with Green Manure

As the growing season winds down and autumn sets in, it’s a great time to start thinking about how to restore and prepare the soil in your vegetable patch for the next year’s crops. Replenishing your soil now will ensure that your plants have the nutrients they need to thrive when spring rolls around. One of the simplest and most rewarding ways of doing this is by planting green manure!

Why Replenish Your Soil?

After a full growing season, your soil can become depleted of nutrients, especially if you’ve been harvesting crops like tomatoes, courgettes, or beans. Without replenishing these nutrients, next year’s crops might struggle to thrive. Over time, your soil’s structure can also degrade, leading to compaction, poor drainage, and reduced aeration. Rejuvenating your soil now will give it time to rest and regain its vitality over winter.

Using Green Manure to Boost Soil Health

One of the most effective ways to replenish and protect your soil through the colder months is by sowing green manure. Green manure crops are fast-growing plants that are sown specifically to cover and protect the soil, adding valuable nutrients and organic matter as they grow and decompose.

Which One Should I Use?

White mustard – Sinapis alba

Mustard is a fast-growing green manure that can be sown from March to September, maturing in 4-8 weeks and reaching 60-90 cm tall. It thrives on most soil types, especially fertile ones, though it may need extra water in dry conditions.

It produces large amounts of green matter and fibrous material that improve soil texture and moisture retention, especially in sandy soils. Though it doesn’t fix nitrogen, mustard quickly lifts available nitrogen, enhancing soil fertility. Additionally, it may help reduce wireworm populations and help protect crops like potatoes.

This is not the hardiest green manure variety but it may survive a mild winter. Frosted foliage can be left on the soil as mulch, where it will gradually break down, aided by worms, with the rest being dug into the soil in early spring.

Phacelia tanacetifolia

Phacelia Tanacetifolia is a fast-growing, hardy annual green manure that germinates in low temperatures, ideal for sowing from March to September. It grows up to 1m and tolerates cold, making it suitable for most soils, especially dry ones.

Though it doesn’t fix nitrogen, Phacelia holds nitrogen and produces dense foliage that smothers weeds and improves soil structure. Its flowers attract beneficial pollinators, and is in fact one of the top 20 honey-producing flowers for honeybees! To prevent self-seeding, dig it in before flowering. It’s also a great choice for crop rotation and provides a long-lasting cut flower.

Crimson clover – Trifolium incarnatum

Crimson Clover is an excellent green manure for smothering weeds, fixing nitrogen, and improving soil structure with its deep roots and bulky foliage. While not always winter-hardy, frosted foliage can be left as mulch and dug in during spring. If it survives winter, it produces crimson flowers that attract bees and beneficial insects.

Autumn/winter mix

This combination of Crimson Clover, Broadleaf Clover, Westerwoths Ryegrass, and White Mustard makes an effective green manure mix by combining their unique strengths. Crimson Clover and Broadleaf Clover fix nitrogen into the soil, smother weeds, and improve soil structure with its deep roots. Westerwolths Ryegrass serves as a fast-growing nitrogen lifter, helping retain nitrogen in the soil, while its dense roots improve soil aeration and drainage. White Mustard grows quickly, producing large volumes of green matter and fibrous material to improve soil texture and moisture retention, and it also suppresses pests like wireworms.

Together, they provide balanced nitrogen fixation, organic matter, weed control, and soil improvement, making the mix versatile for various soil conditions and crop rotation plans.

How to Use:

Simply sow seeds directly onto cleared soil after harvesting your summer crops. You can leave the plants to grow through winter, and come spring, dig them into the soil to release their nutrients.