Tuberous vetchling Lathyrus tuberosus L., [LTHTU, gesse tubereuse, Earth-nut pea, Everlasting pea, Perennial pea, Vetchling, Wild pea, macusson, châtaigne de terre] Perennial reproducing by many underground tubers (like small potatoes and by seed. Stems 20 - 100cm (8 -40 in.) long, slender, hairless, wingless, much-branched, weak and usually sprawling in a tangled mass; in spring and summer usually coming directly from small, potato-like tubers which may be as much as 40 cm (16 in.) deep in the ground; leaves compound and alternate (1 per node) but appearing simple and opposite (2 per node) because each compound leaf consists of 2 stalkless, opposite leaflets and a slender, 3-branched tendril rarely (1- or 2-branched) at the end; leafstalk (between the 2 leaflets and the stem) short, 8 - 20 mm (1/3 - 4/5 in.) long, slender, wingless, and with a pair of slender, pointed stipules about 1 cm (2/5 in.) long on either side where it joins the stem; each individual leaflet narrowly elliptic, 2 - 5 cm (4/5 - 2 in.) long, pointed at both ends; flowers pink to violet, resembling a Sweet pea in colour, shape and fragrance, in groups of about 5 (2 to 10) on long, erect stalks from the leaf axils; seedpods light brown, about 2 cm (4/5 in.) long and usually containing 2 to 3 greenish to brownish seeds. Flowers from June to September.
Tuberous vetchling occurs in cultivated fields, pastures, meadows, orchards, old gardens, edges of woods, roadsides and sometimes in gravel quarries in scattered locations in southern Ontario.
Before flowering, it is distinguished by its slender, non-winged, weak stems with alternate, compound leaves having just 2 opposite leaflets plus a 3-branched, thread-like tendril and reproducing from numerous, small, potato-like tubers. Everlasting pea, Lathyrus latifolius L., [LTHLA], gesse à feuilles larges, gesse vivace], resembles Tuberous vetchling but is a larger, coarser plant with broadly winged stems, winged leafstalks and does not reproduce by tubers.
(Source: Ontario Ministry of Agriculture and Food, Publication 505, Ontario Weeds)
