Pinguicula (Butterwort)

A pinguicula is a carnivorous plant commonly referred to as a butterwort. They grow in nutrient-poor, alkaline soils throughout the northern hemisphere. There are roughly 80 currently known species, 13 are native to Europe, 9 to North America, and some to northern Asia. The largest number of species is in South and Central America.

Pinguicula have adapted to make up for this lack of nutrient soil by luring, trapping and digesting live prey with sticky, glandular leaves. These areas of habitat are almost constantly moist or wet. Some species have adapted to other soil types, such as acidic peat bogs (ex. P. vulgaris, P. calyptrata, P. lusitanica), soils composed of pure gypsum (P. gypsicola and other Mexican species), or even vertical rock walls (P. ramosa, P. vallisneriifolia, and most of the Mexican species). A few species are epiphytes (P. casabitoana, P. hemiepiphytica, P. lignicola). Many of the Mexican species commonly grow on mossy banks, rock, and roadsides in oak-pine forests.

Pinguicula have two growth cycles. When conditions are wet they are carnivorous. When conditions are dry, they are non-carnivorous and resemble a cactus. Many Mexican species lose their carnivorous leaves, and sprout succulent leaves, or die back to onion-like “bulbs” to survive the winter drought, at which point they can survive in bone-dry conditions. The moisture they need for growth can be supplied by either a high groundwater table or by high humidity or high precipitation. Unlike many other carnivorous plants that require sunny locations, many butterworts thrive in part-sun or even shady conditions.

There are four groups of Pinguicula. These four are:

Tropical butterworts: species which do not undergo a winter dormancy but continue to alternately bloom and form rosettes.

Heterophyllous tropical species: species that alternate between rosettes of carnivorous leaves during the warm season and compact rosettes of fleshy non-carnivorous leaves during the cool season. Examples include P. moranensis, P. gypsicola, and P. laxifolia.

Homophyllous tropical species: these species produce rosettes of carnivorous leaves of roughly uniform size throughout the year, such as P. gigantea.

Temperate butterworts: these plants are native to climate zones with cold winters. They produce a winter-resting bud (hibernaculum) during the winter.

Heterophyllous temperate species: species where the vegetative and generative rosettes differ in shape and/or size, as seen in P. lutea and P. lusitanica.