Pinguicula villosa — Vorstman's Guide to the Carnivorous Plants

Identification

A minute rosette of leaves eight to ten millimetres long and four to six wide, with inrolled margins, usually half sunk into the bog moss. The epithet refers not to the leaf but to the scape: thirty to sixty millimetres tall and distinctly clothed in long awl-shaped hairs, obvious at once under a lens and the best field character of the species. The flower is pale violet, six to nine millimetres long, with yellow stripes in the throat serving as a nectar guide; the spur is cylindrical to conical and two to three millimetres long, about half the length of the rest of the flower. After flowering the plant withdraws into a winter bud, which passes the long, deeply frozen winter under snow.

Similar species

Pinguicula vulgaris and P. alpina occur in the same country, but both are two to four times larger and have a glabrous scape; that last character alone settles it. In Siberia and the Russian Far East there are also P. algida and P. spathulata, likewise small species, but with a white to three-coloured flower and without the conspicuous hairy scape. A butterwort on a Sphagnum hummock smaller than a fingernail and with a hairy stalk can safely be taken for this species.

The trap and how it works

A flypaper trap with minimal surface area, which means every leaf counts. The stalked glands hold a droplet that on open bog would dry quickly in wind and sun were the plant not sitting just above permanently damp bog moss; the sessile glands beneath release enzymes only once prey is lying there, and the margin then rolls slowly inwards. The supply on a raised bog is limited to small flies, springtails and mites, but in the short northern summer these swarm in enormous numbers. Sphagnum peat, with its extremely low nitrogen content and acid water, is perhaps the poorest substrate in the northern hemisphere — exactly the setting where a catch makes the difference.

Habitat and ecology

Raised bog and Sphagnum hummocks in the boreal and subarctic zone (W1), almost always on the hummock crowns rather than in the wet hollows, and on the peaty floor of open, swampy conifer woodland and muskeg (B4). The plant sits with its rosette on living bog moss, which grows upward with it; the water is acid and extremely nutrient-poor. The site is open, because in the hollows the plant would drown and under a closed canopy it would disappear. It often grows with cranberry, bog rosemary and sundew — a classic raised-bog community.

Distribution and elevation

A circumboreal distribution: from Scandinavia and Lapland through northern Russia and all of Siberia to the Russian Far East and North Korea, and on across the Bering Strait through Alaska and Canada. The species is absent from Greenland, Iceland and Spitsbergen, which stands out in an otherwise continuous northern range. It is thus anything but endemic. In Europe it reaches no further south than the boreal zone of Fennoscandia and northwestern Russia; it has never been found in the Low Countries and, given the climate, is not to be expected there.

Recorded (quarter-degree cells)

Distribution based solely on records at GBIF (Global Biodiversity Information Facility), not on TDWG regions — those are often far larger than the actual range. The light halo is the area around a record, the dark core the record itself. The darker cells are 556 quarter-degree squares in which the species has actually been recorded, from GBIF and only from records accurate to within five kilometres. They show where it has been seen, not where it occurs: an empty square means nothing. For threatened species this layer never goes finer than a whole degree, deliberately.

Forms and variation

No wild varieties are recognised, and for a species with so large a range P. villosa is remarkably uniform. What varies is mainly size: plants on an exposed hummock crown stay smaller than those sheltered by dwarf shrubs, and the scape is shorter in the far north. The intensity of the violet in the flower ranges from nearly white to clearly lilac. Natural hybrids with P. vulgaris have been described where the two share a mire; they are rare, intermediate and almost always sterile, and belong in this guide with the parents.

Where and when to see it

Go onto a raised bog in June or July and look at the hummocks, not the hollows. This plant sits almost always on the dry crown of a Sphagnum hummock, among the moss heads, and is so small that standing up you will never see it. Get on your knees and look for the stalk: a few centimetres tall, hairy, with one pale lilac flower on top. The stalk is what you find, not the rosette. Tread carefully — hummocks recover slowly — and use a lens, because without magnification the hairs are invisible.

Conservation status

The species is assessed as Least Concern on the global IUCN Red List, which given its range is understandable: it occurs across a belt thousands of kilometres wide through Eurasia and North America, in a landscape type still present at those latitudes in enormous extent. It is not listed in CITES. Locally the picture differs. At the southern edge of the range — Fennoscandia, the Baltic states, southern Canada — much raised bog has been drained for forestry and peat extraction, and there the species appears on national red lists. In the longer term the largest uncertainty is thawing permafrost and the drying of northern mires; that affects not a single population but the habitat as a whole.

Scientific name

Pinguicula villosa | Linnaeus, 1753

Described by Carl Linnaeus in 1753, in Species Plantarum, 1st edition: 17. The species occurs in the northern part of the Northern Hemisphere, in boggy, arctic-alpine and subarctic areas. The name "villosa" is Latin for "hairy, shaggy" and refers to this species' notably hairy flower stalk, with long, awl-shaped hairs.

World Checklist of Vascular Plants (WCVP), via Plants of the World Online (POWO), Royal Botanic Gardens, Kew.