Pinguicula cyclosecta

The most purple of the Mexican butterworts. Its leaves flush violet to deep plum thanks to intracellular pigments, especially around the margins and under stronger light, turning whole rosettes a striking violet-green. The species name comes from the circular outline of the corolla: five rounded petals overlapping into a near-perfect disc, intensely violet on the face, paler with dark veining on the back. It is also the smallest of the so-called orchid-flowered butterworts, a small group that includes P. moranensis and P. colimensis.

It grows on vertical, north-facing limestone cliffs in the Sierra Madre Oriental, on the border of Nuevo León and Tamaulipas, between 450 and 2050 m in oak or pine-oak forest. Plants wedge themselves into thin carpets of moss in the company of Selaginella and small agaves, taking cool humid summers and a dry winter rest from November to April.

Summer rosettes carry 6 to 12 obovate-spathulate leaves up to 6 cm long, with a long wedge-shaped petiole that makes up most of the leaf. In winter the plant contracts into a tight cluster of small succulent leaves fringed with hairs. Flowers appear from May, single on slender stalks, up to 4 cm long including the curved spur. The five almost-circular petals overlap into the disc that gives the species its name, and the violet of the inner surface fades through purple to a near-white throat with fine pale violet veins.