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U.S. Forest Service

Plant of the Week

Map of the United States showing states. States are colored green where the species may be found. Range map of Orobanche uniflora. States are colored green where the species may be found.

Closeup of flower of Orobanche uniflora showing the six tepals. Orobanche uniflora. This photo was taken in the Hells Canyon National Recreation Area, Idaho. This specimen was on a flat area on the east bank of the Snake River, just below the Hells Canyon Dam. Photo by Chantelle DeLay, Payette National Forest.

Orobanche uniflora in habit. Orobanche uniflora. Photo by Tom Barnes.

One-flowered Cancer Root (Orobanche uniflora L.)

By Chantelle DeLay and Terry Miller

One flowered cancer root — also called one-flowered broomrape — is a native annual found from Vancouver Island and Southern British Columbia south to California, east to Florida and Newfoundland. This species is often found in damp woods and thickets, and open places from lowlands to moderate elevations in mountains. The plant consists of a 3-10 inch stem with a single purple to white flower with a bilabiate corolla and no bractlets. The calyx is cleft deeply into five subequal lobes, which are greater than the tube.

A fascinating aspect of the biology of this species is expressed by is brownish stems and minute scale-like leaves. This plant does not contain chlorophyll, and is dependant on other plants to produce nutrients. The species is parasitic on a wide array of species to include the genus Sedum and members of the families Saxifragaceae and Asteraceae. Given the species wide distribution, this is somewhat expected. It is fun to look at the surrounding flora, and guess which plant might be biologically connected to one flowered cancer root. Members of the genus Orobanche were once considered to be part of the family Scrophulariaceae.  Recent taxonomic evidence indicates that the genus and other parasitic members of Scrophulariaceae be placed in the family Orobanchaceae.

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