- Latin synonym: Vicia tetrasperma
- Name also: Lentil Vetch, Smooth Vetch, Sparrow Vetch, Slender Vetch
- Family: Pea Family – Fabaceae (Leguminosae)
- Growing form: Annual herb. Taproot quite long.
- Height: 15–60 cm (6–25 in.). Stem branched, climbing, bristly, almost glabrous.
- Flower: Corolla zygomorphic, light purple, 5–8 mm (0.2–0.32 in.) long. Petals 5; the upstanding the ‘standard’, the lateral two the ‘wings’, the lower two united to form the ‘keel’, overall shape of corolla being butterfly-like. Calyx 5-lobed, lobes short. Stamens 10, filaments with fused bases. A single carpel. Inflorescence long-stalked, 1–3-flowered raceme.
- Leaves: Alternate, stalked, stipulate. Blade pinnate, 3–5 pairs, terminal leaflet modified into a tendril. Leaflets linear, narrow, tips quite round, with entire margins. Stipules entire.
- Fruit: 9–15 mm (0.35–0.6 in.) long, glabrous, brown, usually 4-seeded pod (legume).
- Habitat: Meadows, rocks, dry meadows, precipices, roadsides, wasteland, fields.
- Flowering time: June–August.
Smooth tare is one of the most delicate plants in its genus. It is quite common, especially in the Åland Islands, south-western Finland’s archipelago and the south of the country, but this delicate climbing plant often goes unnoticed among grass and hedgerows and other vegetation. Smooth tare is modesty itself: its stems are thin, its leaflets are narrow and its flowers are small. It is regarded as a native of the Mediterranean region and western Asia, and from this area it spread very early on around Asia and Europe. In Finland it is often regarded as a native, meaning that it has been a part of our nature for so long that there is no longer any way of knowing when it first arrived. In any case the species has spread to Finnish shores also among ballast soil on sailing boats and with other maritime traffic, and also during the last war with German soldiers. Smooth tare has also travelled with people to Australia.
Hairy tare (Ervilia hirsuta) is very reminiscent of smooth tare, but its flowers are white and it has more leaflet pairs than smooth tare. Perhaps the easiest way to differentiate between the species is by the number of seeds in the pod: hairy tare has two seeds while smooth tare has four.