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Pinguicula lignicola
Butterworts are plants of wet ground and dripping rock — with one kind of exception, and this is one of them. Pinguicula lignicola grows not on soil but on bark: a true epiphyte, fixed to the trunks and branches of trees and shrubs in the mountains of eastern Cuba, including Cuban pine. Of the hundred-odd butterworts in the world only two do this, and the other one lives on Hispaniola.
Identification
A small, delicate rosette lying flat against the bark, with thin, pale green leaves glistening on top with glandular droplets. The plant is not anchored into the wood the way a tree is rooted in soil, but hangs from a collar of rootlets and root hairs gripping the rough bark. Because the rosette is so small and flat, on a mossy trunk it disappears easily among liverworts and small ferns. The scapes are slender and each carries a single flower. When in doubt, look for the glossy, wet-looking leaf surface — moss shines differently from a glandular coat. Flower and fruit matter less in this species than usual, because reproduction runs by a different route from almost all its relatives: what drops from the calyx is not a seed but already a small plant.
Similar species
The same trunks carry liverworts, small ferns and epiphytic orchids; from all of these the butterwort rosette is told by its greasy, droplet-covered surface and its entire, undivided leaves. The only other epiphytic butterwort, Pinguicula casabitoana, lives on Hispaniola and does not overlap, so an epiphytic Pinguicula in Cuba is by definition this species. Confusion with ground-living Cuban butterworts such as P. jaraguana or P. moaensis arises only if you ignore where the plant sits: those grow on wet rock or stream banks, never on a trunk.
The trap and how it works
The trapping apparatus is that of an ordinary butterwort — stalked glands with a sticky droplet, sessile glands releasing enzymes — but it works here in a completely different water economy. An epiphyte has no soil moisture; it lives on what cloud and rain deliver, and those supply even less mineral nutrition than a poor forest floor. That is exactly why catching insects here is not a luxury but the main source of nitrogen and phosphorus. The rosette takes what walks and flies on bark: springtails, mites, small flies and midges of the permanently damp trunk layer.
Habitat and ecology
The species wants bark that is almost always wet: micro-habitats with permanently high humidity and frequent, reliable wetting by cloud and rain. Labels on old material say simply 'on branches of trees', and record sites along streams, where the air stays trapped between the banks. The setting is the ultramafic mountain country of eastern Cuba, where pine woodland and low scrub on serpentine soils alternate and the trees stay short and rough-barked — exactly the kind of trunk such a rosette can hold on to. Where exactly the rosettes sit is decided by the bark: a rough, lightly furrowed surface holds moisture and offers purchase, while smooth, flaking trunks give too little grip. Aspect relative to the prevailing wind counts too, because the side the clouds strike stays wet longest.
Distribution and elevation
Endemic to Cuba and confined to the east: Guantánamo and Holguín provinces, with records from Minas de Iberia and Yateras near Baracoa, from El Toldo and from around Moa. A 1914 label at Minas de Iberia gives eight hundred metres; other finds lie lower. This is a small, fragmented range in one of the botanically richest and simultaneously most pressured corners of the Caribbean, where nickel mining on serpentine soils and forest change dominate the landscape.
- Recorded (one-degree cells)
Forms and variation
No wild subspecies or varieties are recognised. What is striking is how closely the plant follows its host: on coarse, deeply furrowed bark the rosettes sit deeper in the fissures and stay smaller than on smooth young branches. Its most remarkable property, though, is not a form but a mode of reproduction: true vivipary has been demonstrated in this species. What the plant releases are not seeds but seedlings, formed inside the calyx, which attach themselves to bark with an unbroken ring of root hairs — first described for Pinguicula here and shared with the epiphyte of Hispaniola.
Where and when to see it
Look up rather than down. Search along stream valleys in the hills, on the damp north side of trunks and on low branches, and note where moss and liverwort already show that the bark seldom dries. After rain or in morning mist recognition is easiest, because the glandular coat shines then. Binoculars are not a luxury: many rosettes sit above eye level. Bear in mind that the best areas lie inside protected mountain reserves.
Conservation status
The species has not been assessed for the global IUCN Red List and is not listed in CITES. What is known: a Cuban endemic with a small number of eastern sites, wholly dependent on host trees in a permanently humid forest layer. That makes it sensitive to exactly the changes at work in this region — logging, nickel mining on the serpentine soils, and a drying climate that reduces cloud wetting. Without a global assessment there is no formal category; its absence here is a gap in the file, not reassurance.
Scientific name
Pinguicula lignicola | Barnhart, 1920
Described by John Hendley Barnhart (in Nathaniel Lord Britton, 1920), in Memoirs of the Torrey Botanical Club 16(2): 110, based on a specimen collected by J.A. Shafer on 23 February 1910 (collection number 4031). The type locality is the vicinity of Camp San Benito, in what was then Oriente Province (now Holguín), Cuba, where the plant grew epiphytically on tree branches. The name derives from the Latin lignum (wood) and -cola (dweller of), referring to this species' epiphytic growth on tree branches.
World Checklist of Vascular Plants (WCVP), via Plants of the World Online (POWO), Royal Botanic Gardens, Kew.