Annual plant (Lathyrus odoratus) of the pea family (seelegume), native to Italy and widely cultivated elsewhere for its beautiful, fragrant flowers. The long (4–6 ft, or 1.2–2 m), vinelike stem climbs by means of tendrils and bears featherlike leaves. White, pink, red, violet, or purple flowers, reminiscent of butterflies in shape, are borne singly or in clusters of two to four. The fruit is a hairy pod about 2 in. (5 cm) long. Hundreds of varieties of sweet pea have been developed. The plant was the subject of important genetics experiments by Reginald Crundall Punnett and William Bateson.