- Name also: White Swallowwort
- Family: Dogbane Family – Apocynaceae
(formerly Swallow-wort Family – Asclepiadaceae)
- Height: 30–70 cm (12–28 in.). Stem erect, stout, glabrous.
- Flower: Regular (actinomorphic), ca, 1 cm (0.4 in.) across. Corolla of 5 basally fused, white petals. Corolla-lobes thick, tapering but blunt-pointed. Calyx of 5, fused, triangular, sharp-pointed almost hairless sepals with a narrow membranous margin. Corona 5-parted. Stamens 5. Gynoecium of 2 carpels. Flowers in whorls forming a raceme.
- Leaves: Opposite, short-stalked. Blade ovate to lanceolate, with cordate or rounded base and entire margins.
- Fruit: Many-seeded, ca. 5 cm (2 in.) long follicle, paired. Seed crowned by a dense tuft of white hairs.
- Habitat: Rocky and dry hillocks, rock outcrops.
- Flowering time: June–July.
Swallow-wort is a limestone-favouring perennial. It thrives on sunny and warm sites. This species is the northernmost European species of the family Asclepiadaceae which is concentrated in the tropics. As the generic name suggests (Vincetoxicum, Latin for ‘conqueror of poison’), this plant has been used as an antidote, e.g. to snake’s poison. Drugs made chiefly from the rootstock of the plant have also been used in treating diseases and ailments. In the archipelago the swallow-wort was even cultivated to some extent. There it can still be encountered in margins of yards.
The floral structure of this species, and indeed the whole family, is fairly difficult to grasp. It is very well adapted to insect pollination. The two carpels have united at the top into a shield-like structure on the underside of which is the stigmatic surface. The five stamens are united with the gynoecium. The two outer pollen-sacs of each stamen have transformed into petal-like appendages forming a corona. The two inner pollen-sacs have fused to the pistil right under the stigmatic surface. The pollen is packed into two pollinia connected by a so called translator which in this species is reddish. With the translator the pollinia attach themselves to the legs or proboscis of pollinating insects.