Alpine butterwort (Pinguicula alpina)

Description

Pinguicula alpina, also known as the alpine butterwort, is a species of carnivorous plant native to high latitudes and altitudes throughout Eurasia. It is one of the most widespread Pinguicula species, being found in mountainous regions from Iceland to the Himalayas. Native to cold climates, it is a temperate species, forming prostrate rosettes of green to red leaves and white flowers in the summer and a tight hibernaculum during a period of winter dormancy in the winter. Like all members of the genus, P. alpina uses mucilagenous glands covering the surface of its summer leaves to attract, trap, and digest arthropod prey. P. alpina is a small perennial herb, reaching a height of 5–15 cm (2-6 in.) when in flower. The plant is supported by 1–2 cm (0.4-0.8 in) long roots, which are fleshy, yellow-white and branching. P. alpina is the only temperate Pinguicula which retains these roots year-round; the roots of other temperate species wither with the winter dormancy. This allows it to invest more of its income (nutrients derived from prey) into long-term storage, compared to other subarctic Pinguicula which are income breeders and invest these nutrients into immediate plant size and flowering increases. The five to eight fleshy, light-green to reddish, elliptic to lanceolate leaves form a ground-hugging rosette up to 6 cm (2.5 in) in diameter. The upper surface of the leaves are sticky from the mucilage secreted by stalked glands covering the leaf surface. Small insects alighting upon this surface are caught by the mucilage, upon which sessile glands embedded in the leaf surface (except for the central vein) secrete digestive enzymes to digest the prey. The leaves of this species are able to further aid digestion by growing such that the leaf edge rolls toward the center, bringing additional glands into contact with the prey. Most plants are reddish-green in full sun, though some plant will turn completely red while a smaller percentage will remain completely green. P. alpina only begins flowering after several years of growth. Six to eight (occasionally up to 13) flowers are borne singly on unbranched inflorescences up to 12 cm (5 in) tall. The zygomorphic flowers are 10–16 mm (⅜-⅝ in) long with a short yellow-green spur and are composed of a two-lobed upper lip and three-lobed lower lip. They are white with one or sometimes three yellow markings on the lower lip. These can be variable in size and shape. The flowers are protogynous, meaning that the female stigmas mature before the male anthers, and are pollinated by flies. Fertilized flowers mature into 6–9 mm (¼-⅜ in) by 2–3 mm (1/16-⅛ in) seed capsules bearing copious numbers of tiny, rust-brown seeds.