Pinguicula lusitanica — Vorstman's Guide to the Carnivorous Plants

Identification

A small flat rosette of oblong leaves seven to thirty millimetres long, with strongly inrolled margins. The leaf is olive-green and marbled with purplish-red veins — a character no other European butterwort has, and one that identifies the species at once even out of flower. One to six slender glandular scapes up to twenty centimetres rise from the rosette. The flower is small, five to nine millimetres, pale lilac to pinkish with a distinctly yellow throat; the spur is blunt, recurved and yellowish, two and a half to four and a half millimetres. Flowering is March to May, continuing into August in cooler districts. The plant is short-lived and seeds abundantly.

Similar species

Pinguicula vulgaris occurs in the same country and, in the Pyrenees, P. grandiflora and P. longifolia; all three are considerably larger, with a violet to blue-purple flower over fifteen millimetres and plain green leaves. The purple-veined leaf and the small pale flower with a yellow throat make P. lusitanica unmistakable. A second difference shows in winter: where the other European species withdraw into a bud, this one simply stays in leaf. A butterwort rosette found in western Europe in midwinter is almost certainly this species.

The trap and how it works

A flypaper trap that runs all year — unique among the European species. The stalked glands carry a sticky droplet, the sessile glands beneath release digestive enzymes as soon as prey is lying on the leaf, and the margin rolls slowly inwards. Because the plant stays active in winter, in the mild Atlantic climate it still catches small insects in the dark months. The rosette is small, so the yield per plant is modest; against that, the species is short-lived and produces much seed, so the investment per individual stays low. On acid, leached soils with almost no mineral nutrition that is a workable strategy.

Habitat and ecology

Wet heath and pool margins on acid sandy or peaty ground (W4), the banks of rills and ditches (W7), damp grassland and mire edges (W6), and — more than most butterworts — man-made wet ground such as verges, ditch sides and freshly cut peat workings (H1). The species is a pioneer: it appears quickly on open, wet ground and goes again as soon as the vegetation closes. The soil is always acid and lime-poor; elevation runs from ten to twelve hundred metres, with the emphasis on the lowlands.

Distribution and elevation

A markedly Atlantic distribution: Portugal and the western half of Spain, western France, Ireland and western Britain into Scotland, plus an occurrence in northwestern Africa. The species is therefore not endemic. Our own species list gives 'Portugal to Scotland', which sums up the European part well but leaves out the Moroccan portion of the range. It does not occur in the Low Countries; the nearest populations are in western France.

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 277 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. Variation lies in the intensity of the purplish leaf veins — stronger in full light than in shade — and in flower colour, which runs from almost white to clearly pink. The number of scapes per plant also varies widely with growing conditions. Because the species is short-lived and renews itself from seed, populations can differ greatly in size from year to year with nothing being wrong. No natural hybrids with other butterworts have been described; the species stands rather isolated within the genus.

Where and when to see it

Search in spring on open, wet, acid ground — and think especially of places where the soil has recently been opened: the edge of a ditch, a path across wet heath, a stripped patch, the bank of a rill. The rosette is small and pale but the marbled leaf is highly characteristic; get on your knees and use a lens. The flower is pale and small and hardly noticeable, so use the leaf as your search image. Because the plant stays in leaf through winter, there is something to find out of season too.

Conservation status

The species is assessed as Least Concern on the global IUCN Red List and is not in CITES. That fits a range reaching from Morocco to Scotland and a pioneer that colonises new wet ground quickly. Regionally the picture is less favourable. At the eastern edge of the range, in France and parts of Spain, much wet heath has been drained, fertilised or planted with conifers, and there the species appears on regional red lists. In Britain and Ireland losses come mainly from straightening and deepening ditches and from the closing over of ungrazed wet heath. As a pioneer it benefits, on the other hand, from management that opens the ground — a species that lets itself be helped.

Scientific name

Pinguicula lusitanica | Linnaeus, 1753

Described by Carl Linnaeus in 1753, in Species Plantarum: 17. The species occurs along the Atlantic coast of western Europe, from Portugal and Spain to Britain and Ireland. The name "lusitanica" refers to Lusitania, the Roman name for the region roughly corresponding to Portugal, from where Linnaeus had material of this species.

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