Pinguicula vulgaris

A butterwort for half the northern hemisphere

No other butterwort covers as much ground. Legendre and Cieslak describe a range that takes in Greenland, Iceland, most of the northern half of North America and a large part of Europe, from the far north to the Mediterranean and east to the Urals ^[2]. WCVP extends the native range across Siberia to Mongolia ^[1]. Most other butterworts, by contrast, are known from a few small, isolated places ^[2]. Within the genus it belongs to section Pinguicula, the temperate species that form winter buds ^[10].

Such a wide range brings variation. Casper’s 1966 monograph listed 24 named variants below species level, but only two flower-color forms, f. bicolor and the pale f. albida, were kept as distinct; Steiger later added var. transsilvanica ^[2]. Fleischmann notes that pale-flowered plants turn up fairly often among normally colored ones in many European populations ^[10]. In Legendre and Cieslak’s comparison of cultivated plants from several countries, rosettes ranged from about 4 to 17 cm across and depended heavily on growing conditions, while calyx and corolla size stayed fairly constant ^[2].

Acid bogs, alkaline fens and wet cliffs

P. vulgaris is not choosy about soil chemistry. It grows on calcareous cliffs, on acid ground (pH 4.9 has been measured in Greenland) and on gypsum at pH 5.7 to 8.2 in the western Pyrenees ^[2]. Near Reims in France, the three remaining populations of the Champagne region grow in alkaline bogs with hard water and no Sphagnum, where a spring emerges and sand, clay and chalk mix; the soil pH next to the plants was about 6.5 ^[2].

The same study shows how light shapes the plant. Rosettes were largest in deep shade but rarely flowered and caught few insects. Plants in full sun were small, flowered once and had dry leaves without mucilage. Plants with plenty of light but no direct sun did best on all counts. Most captures happened at night or early in the morning ^[2].

A winter bud that seldom splits

In autumn the plant pulls back into a hibernaculum, a tight winter bud ^[9]. In P. vulgaris the outer bud scales cover the whole bud, and the bud does not pull itself under the soil ^[2]. Unusually for its section, it rarely produces daughter buds. Most plants in the French comparison made one per year at most, often none, while relatives such as P. grandiflora make many ^[2]. The Champagne plants were the exception, producing 20 to 28 gemmae per bud and round rather than pear-shaped seed capsules ^[2]. So most plants offer few offsets to divide.

Chromosome counts set it apart from its relatives too. Mrkvicka notes that P. vulgaris has the highest chromosome number in its section and regards it as the youngest and most successful member ^[6]. Steiger gives 2n = 64, twice the 32 of P. grandiflora ^[11].

Names and look-alikes

WCVP treats P. borealis as a synonym ^[1]. In western North America the closely related P. macroceras is handled differently by different authorities. NatureServe follows a narrow concept that keeps it as a separate species, but notes that some floras, including a 2025 treatment, rank it as a subspecies of P. vulgaris ^[3]. ICPS lists it separately, from Japan, eastern Russia and western North America ^[9].

A hybrid with P. alpina, named P. ×hybrida in 1919, is still repeated in the literature. Fleischmann doubts it exists: the two species grow side by side in the Alps, yet more than 20 years of his crossing attempts produced no seed, and he suspects the original plants were pale-flowered P. vulgaris ^[10].

Status in the wild

The 2016 Irish Red List rates it Least Concern in Ireland ^[12]. IUCN has also assessed the species; see its Red List assessment ^[4]. Losses are local but real. At the southern edge of its North American range NatureServe ranks it critically imperiled (S1) in Maine, New Hampshire, Vermont and Wisconsin, and imperiled to critically imperiled in New York and Nova Scotia ^[3]. The three Champagne populations fell from an estimated 12,200 plants in 1994 to 2,110 in 1999. The authors blame past wetland drainage for most losses in the region and suspect that the end of horse grazing, overgrown grass and drier air drive the continuing decline; at one site, water diverted from an upstream lake also played a part ^[2]. A well-meant clearing of trees and grass at one site in 2000 nearly wiped out that population, though it later recovered ^[2]. Germany lists wild populations as specially protected ^[5].

Growing it

Treat it as a cold temperate butterwort: a cool, bright summer and a real winter rest. In a mild coastal climate it can live outdoors all year; ICPS describes it thriving with other cold-hardy carnivores in a bog garden of 50:50 peat and sand in North Vancouver ^[13]. See bog gardens.

Where winters are too warm, Barry Rice’s refrigerator method is the standard workaround ^[8]:

1. Grow plants in small pots, about 5 cm (2 in), in a 50:50 silica sand and peat mix, standing in purified water.
2. In terraria, cut the day length to about 75% of the summer value, for example from 16 to 12 hours, to trigger bud formation.
3. When the old leaves have rotted away around a tight bud, clean off dead material, repot if needed, and seal the pot in a plastic bag in the refrigerator.
4. Check monthly. When the bud opens, wait a few more weeks before bringing the pot back into the light.

Rice adds that plants can be shifted gradually so they grow in winter and rest in summer, which suits hot climates. He also warns that the short growing season means plants may take a few years to reach flowering size ^[8]. The dormancy guide compares winter methods.

From seed

Seed needs 8 to 12 weeks at -10 to 5°C before it will germinate. In cold-winter areas, sow outdoors in early autumn and expect seedlings between March and May; otherwise stratify the seed in a small bag with damp peat in the coldest part of the refrigerator, ideally in winter, and grow the seedlings on a natural day length ^[9]. See cold stratification and sowing seeds. In the French trial, seedlings from most populations needed two to three years to flower ^[2].