Lupin, often spelled lupine in North America, is the common name for members of the genus Lupinus in the legume family (Fabaceae). The genus comprises between 200-600 species, with major centers of diversity in South America and western North America – subgen.Platycarpos) and subgen. Lupinus – in the Mediterranean region and Africa.
Lupin leaves from belowThe species are mostly herbaceous perennial plants 0.3-1.5 m (1-5 ft) tall, but some are annual plants and a few are shrubs up to 3 m (10 ft) tall – see also bush lupin -, with one species (Lupinus jaimehintoniana, from the Mexican state of Oaxaca) a tree up to 8 m high with a trunk 20 cm (8 in) in diameter. They have a characteristic and easily recognised leaf shape, with soft green to grey-green leaves which in many species bear silvery hairs, often densely so. The leaf blades are usually palmately divided into 5–28 leaflets or reduced to a single leaflet in a few species of the southeastern United States. The flowers are produced in dense or open whorls on an erect spike, each flower 1-2 cm long, with a typical peaflower shape with an upper ‘standard’, two lateral ‘wings’ and two lower petals fused as a ‘keel’. Due to the flower shape, several species are known as bluebonnets or quaker bonnets. The fruit is a pod containing several seeds.
Like most members of their family, lupins can fix nitrogen from the atmosphere into ammonia, fertilizing the soil for other plants. The genus Lupinus is nodulated by Bradyrhizobium soil bacteria2. Some species have a long central tap roots, or have proteoid roots.