Plant of the Week
Purple Pitcherplant, Saddle Flower (Sarracenia purpurea L.)
The pitcherplant is a perennial forb that spreads by short rhizomes. Plants form an open, spreading rosette of green leaves. The leaves are often tinged or veined with purple, and can grow to 30 cm in length. The plants flower in mid-spring, producing a solitary flower at the top of a scape 20 – 40 cm tall. The flower resembles a thick, flat disc ringed with dark, maroon petals. The plants are most noted, however, for the hollow, gibbous leaves, or pitchers, that give the plant its name.
The pitchers trap and digesting flying and crawling insects, making the species one of the few carnivorous plants in North America. The hollow pitchers fill naturally with rainwater. The pitchers also have broad lips where insects land. The insects crawl into the pitcher, where stiff, downward pointing hairs prevent them from leaving. Anectdoctal evidence suggests pitchers capture less than one percent of the flies that venture into their traps, but a few insects eventually fall into the water at the base of the pitcher, where digestive enzymes secreted by the plant release the nutrients within the insects. Eventually, the nutrients are absorbed by the plant, which supplements the nutrients absorbed by the roots.
At least two insects also use the pitchers as a breeding location. A community of microorganisms eventually develops in the water at the base of the pitchers. These microorganisms live on the nutrients of the decaying insects, and may actually increase the nutrients available to the plant by further digesting its prey. The microorganisms are themselves prey to at least two species of carnivorous insects – the larvae of a mosquito and the larvae of a midge – which complete their life cycles in the pitchers. For some reason, the digestive enzymes secreted by the plant affect neither species.
Pitcherplants are widespread in eastern North America, ranging from the Gulf Coast of the Florida panhandle to Nova Scotia, and across Canada to the base of the Rocky Mountains. Primarily a northern species, isolated populations occur along the Atlantic Coast and in the Appalachian Mountains. Pitcher plants grow primarily in sphagnum bogs, although they can be found in any wetland with long periods of standing water, including roadside ditches.