Pitcher plants
Endemic to North America, pitcher plants from the genus Sarracenia were amongst the first insectivorous to be grown by horticulturists in Europe. The first successful flowering of a cultivated Sarracenia plant was recorded in the late 1700s. The spectacular pitchers and relative ease of cultivation have ensured their continued horticultural popularity. The main requirements for success are nutrient-poor compost, a wet or damp substrate and distinct summer- and winter-growing conditions. A highlight of a visit to the glasshouses at the Botanic Garden is the temperate carnivorous plant collection. Grown in a wetland-type environment and displayed in a naturalistic style, these plants embody the theme of adaptation that unifies the glasshouse collections.
Carolus Linnaeus adopted the generic name Sarracenia from a name the French botanist Joseph Pitton de Tournefort gave to some specimens that were sent to him by Michel Sarrazin, the Father of Canadian Botany. Tournefort is the first botanist to have a clear concept of the genus.
What makes pitcher plants so captivating are their gruesome adaptations for life as a carnivore. The pitchers are modified leaves, adapted to supplement the meagre supplies of nitrogen and phosphorus sarracenias can extract from the nutrient-deficient soils. Numerous mechanisms contrive to lure insects, and spiders, into the pitchers and ensure they drown in a trap of digestive fluid.
Sarracenias are long-lived, herbaceous perennial plants. The pitchers are arranged in rosettes, growing from the tips of woody rhizomes. Pitchers vary hugely in shape and size amongst species of Sarracenia but all have the common feature of an operculum, a lid-like structure at the apex of the pitcher.
Beneath the operculum, the lip or peristome of the pitcher produces nectar to attract prey to the trap entrance. The upper, interior portion of the pitcher is waxy, forming a glass-smooth surface on which insects easily lose their footing.
As the prey plunges into the pitcher, it passes minute downward-facing hairs, making escape impossible. The base of the pitcher is covered in coarser, downward-facing hairs together with glands that secrete the digestive enzymes that extract nutrients from the prey.
All sarracenias are threatened in the wild by development, land drainage and collection for the horticultural trade. Because of the dramatic reduction in habitat and decrease in healthy plant populations, all species have legal conservation protection.
Dried specimens of Sarracenia rubra, collected by the naturalist Mark Catesby in the 1720s, are held in the Oxford University Herbaria.
Further reading
Horner JD and Schatz BA 2016. Resorption of trap nitrogen during senescence and the benefit of prey capture in the carnivorous plant, Sarracenia alata. Plant Ecology 217: 985-991.
McPherson S and Schnell D 2012. Field guide to the pitcher plants of the United States and Canada. Redfern Natural History Productions.
Nelson EC and Elliott DJ 2015. The curious Mister Catesby a "truly ingenious" naturalist explores new worlds. University of Georgia Press.
Kate Pritchard