Trifolium incarnatum

Trifolium incarnatum, also known as crimson clover, is a small perennial plant from the legume family that is used as green manure or as a forage crop. Its roots can fix atmospheric nitrogen, which it then releases into the soil, reducing the need for fertilisers. Its bright red flowers are rich in nectar that feed pollinating insects. Through its root system, it loosens the soil, limits the growth of weeds, and helps prevent soil leaching and compaction caused by rain. Sow after summer crops, from August to September. However, spring sowing in March is also possible.

Crimson clover belongs to the Fabaceae family (formerly known as legumes) and the genus Trifolium, like white clover or Alexandrian clover. These different clovers are characterised by their leaves with 3 leaflets and their ability to fix atmospheric nitrogen in the soil. Crimson clover is an annual plant, originally from the Mediterranean, and widely naturalised in temperate Europe. When not cultivated, it grows in fields, fallow land, along roads or paths, usually on siliceous (sandy) soil. It flowers from April-May to July, in the form of spherical red heads. Crimson clover is highly frost-resistant and develops a significant vegetative cover. It is suitable for all types of soils. It tolerates well-drained soils, but can also grow in clayey or siliceous soil. It does not thrive in limestone soils.

Widely used in organically cultivated gardens, green manures like crimson clover have many advantages. They nourish and improve the soil by providing various nutrients and stimulating soil microbial life. Their roots loosen and aerate the soil, making it more friable and less compact. Moreover, the presence of a vegetative cover protects the soil from leaching (nutrient loss in sandy soil), rain compaction (formation of a crust in loamy soil), and erosion (caused by runoff on sloping terrain during heavy rain). This vegetative cover also helps suppress weed growth. Finally, green manures are often honey-bearing and attract pollinators.

Green manures are sown on uncultivated plots or in intercropped areas between vegetable rows. They are either naturally destroyed by frost or cut before seed formation. Once destroyed, they can be left in place as mulch, or be shredded and incorporated into the top layers of the soil, or be collected and added to compost.