The Narrow-leaved Vetch (Vicia sativa subsp. nigra), also known as Black Vetch or Black Pea, is a flowering plant species native to the United Kingdom. Belonging to the Fabaceae family, it is commonly found in a variety of habitats across the UK, including grasslands, meadows, hedgerows, and arable fields.

Narrow-leaved Vetch has modest nutrient requirements and thrives in well-drained soils with moderate fertility. It is often encountered in sunny or partially shaded locations, where it forms dense mats of foliage and clusters of purple flowers.

In its natural habitat, Narrow-leaved Vetch serves as a valuable food source for various herbivores, including insects, birds, and small mammals, which feed on its nutritious foliage and seeds. However, its bitter-tasting leaves and potentially toxic compounds provide some defence against excessive predation.

As an annual or biennial plant, Narrow-leaved Vetch completes its life cycle within one or two years. In the first year, it typically forms a low-growing rosette of narrow, pinnate leaves close to the ground. In the second year, it sends up flowering stems adorned with clusters of purple pea-like flowers.

Culturally, Narrow-leaved Vetch holds limited significance in the UK beyond its role as a common wildflower and forage crop in agricultural systems. While not widely referenced in literature or folklore, it contributes to the biodiversity and ecological balance of British landscapes.