Pinguicula orchidioides — Vorstman's Guide to the Carnivorous Plants

Pinguicula orchidioides — the trap in close-up — **The trap in close-up** · Photo: NoahElhardt — CC BY-SA 3.0 · Wikimedia Commons

Pinguicula orchidioides — the flower — **The flower** · Photo: NoahElhardt — CC BY-SA 3.0 · Wikimedia Commons

Identification

In the dry season the plant overwinters as an underground bud. In the rains the summer rosette appears with leaves 20 to 46 mm long and 6 to 18 mm wide, spread flat and sticky. The scapes are long for the plant's size: 7 to 22 cm. The flower measures 30 to 48 mm including the spur and is violet-purple; the spur is slender and 18 to 26 mm long, so about as long as the rest of the flower. Flowering is July to September, with the summer rains. A flowering plant with a single large bloom high above a modest rosette is the typical picture. The lower lip in this species is clearly three-lobed with fairly narrow, separated lobes, giving the flower a spare, almost orchid-like look — the epithet refers directly to this. After flowering an erect capsule remains on the long scape, opening only once the rains cease.

Similar species

The confusion lies mainly with Pinguicula moranensis, which grows in the same mountains and likewise has a large violet flower with a long spur; that species generally has more substantial leaves and a differently shaped lower lip. P. macrophylla and P. oblongiloba have distinctly larger leaves on a set-off petiole. Because the name orchidioides was broadly used in older literature, identifications based on old sources are unreliable; for certainty, flower measurements, leaf shape and locality must be considered together.

The trap and how it works

A flypaper trap on a flat leaf, active in the rainy season once the summer rosette has emerged. The stalked glands hold the prey with a sticky droplet and the sessile glands between them supply digestive enzymes on contact; the leaf margin rolls slowly over the prey so the fluid stays in a shallow bowl. The plant lies low in the herb layer of a pine-oak wood and catches mainly small flies and ants there. In the dry months, as an underground bud, it catches nothing. The long scape holds the flower well clear of the sticky leaf, and that is no accident: a plant that catches insects while also needing insects as pollinators must separate those two functions in space. In this species the distance between trap and flower, over twenty centimetres, is among the greatest in the genus in Mexico.

Habitat and ecology

Damp slopes, banks and verges in pine-oak woodland, on reddish-brown to brown clay or sandy-clay soil (B5, D4). The elevation range is wide, from two thousand to twenty-two hundred metres and locally to three thousand, meaning the species grows in cool mountain woods that are dry in winter. It grows in soil, not on rock, and depends on its underground bud to survive the dry season. Open, slightly disturbed spots along paths and verges are often the best sites because competition there is low.

Distribution and elevation

Southern Mexico — Oaxaca and Guerrero — and in addition the department of Sololá in Guatemala. The species is therefore not endemic to Mexico. Our species list gives only 'Mexico'; the published distribution reaches further, into the Guatemalan highlands. These are isolated mountain populations in different massifs, separated by lower and warmer country. Older records from other parts of Mexico rest largely on the broad past application of the name.

Recorded (one-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 8 one-degree squares — roughly a hundred and ten kilometres — in which the species has been recorded, from all GBIF records. This is coarser than for most species because hardly any record of this plant carries an accurate coordinate: the locality of poached species is obscured at source. At this scale that obscuring disappears into the noise. The cells show where it has been seen, not where it occurs: an empty square means nothing.

Forms and variation

No wild varieties are distinguished. Within the species, flower size differs most, running from three to nearly five centimetres, along with the intensity of the violet-purple. Part of the reported variation, however, stems from the historical confusion of names: plants of several species were long brought together under this name, and whatever of that entered older descriptions distorts the picture of the real range. Natural hybrids with P. moranensis have been reported from the area.

Where and when to see it

Go in the rainy season, July to September: the species flowers then and the large violet blooms stand high above the herb layer, visible from far off. Search along paths and verges in pine-oak woodland, on damp, slightly open spots where the soil stays wet through the rains. In the dry months there is nothing to find. Note that other large-flowered butterworts often grow in the same wood; photograph the flower from the side so the spur can be measured, and record the leaf shape.

Conservation status

Not assessed for the global IUCN Red List and not listed in CITES. A distribution across two countries and several mountain massifs looks broad at first sight, but because of the historical confusion of names it cannot be established with certainty how many of the records really concern this species. Pine-oak woodland in southern Mexico and the Guatemalan highlands is being converted to farmland fast and suffers from grazing and fires. Population figures are lacking. An assessment here would make sense only after a critical revision of the herbarium material.

Scientific name

Pinguicula orchidioides | de Candolle, 1844

Described by Alphonse de Candolle in 1844, based on material collected by G. Andrieux in the Mexican states of Oaxaca, Puebla and Mexico. De Candolle placed the species in the section Orcheosanthus, which he newly erected. After a misidentification by William Jackson Hooker at Kew in 1846, the name was long treated as a synonym of another species, until Sergio Zamudio re-established the original identity in 1998. The type material originates from the Mexican states of Oaxaca, Puebla and Mexico (state). The name "orchidioides" (orchid-like) refers to the dainty, orchid-like flowers: a purple, deeply bilabiate corolla with five sub-equal lobes, a short floral tube and a long spur.

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