Linnaeus first descriped Rudbeckia triloba in Species Plantarum in 1753. John Torrey and Asa Gray introduced the variety pinnatiloba in 1841 in A Flora of North America: Containing Bridged Descriptions of all the known Indigenous and Naturalized plants growing North of Mexico arranged according to the Natural System. Only 3 years later, Asa Gray published Synoptical Flora of North America, including the three modern varieties, pinnatiloba, rupestris and triloba.
Rudbeckia triloba has been classified as an endangered species in the state of Florida. (USDA, 2010.)
Rudbeckia triloba is covered in Tennessee under the Rare Plant Protection and Conservation Act of 1985, T.C.A. Section 70-8-301 et seq.
Rudbeckia triloba has a chromosome number of n=19. (Jones, 1970.)
R. triloba grows at a medium rate.
Ray florets of Rudbeckia triloba still contain vestigial stamens. Some corollas in the same head may be three-lobed and five-lobed. (Koch, 1930.)
Var. triloba contains coumarin and two other closely related thiopheneacetylenes. (Gutierrez & Herz, 1990.)
Attempts at hybridization with R. triloba have been unsuccessful. Insect associations include a number of bees and flies, and some wasps, beetles and butterflies.
Rudbeckia triloba is located throughout the eastern United States and up into southeastern Canada, into the central plains and some desert states. Var. pinnatiloba is confined to Virginia, North Carolina, Kentucky, Tennessee, Alabama and Florida. Var. rupestris grows only in North Carolina, Tennessee, Kentucky and Iowa. Var. triloba spans the entire species' range, excluding Florida. (Urbatsch & Cox, 2006.)
For more information, see the map provided by Flora of North America.
Rudbeckia triloba is a preferred source of nectar to a variety of flying insects.
Vars. pinnatiloba and rupestris grow strictly in mesic wetlands, but var. triloba has also been found in roadside meadows, pastures and thickets.
Usually three to several years
Generally sexual, although some polyploids are apomictic.
All varieties flower summer to fall.
Aphids, powdery mildew
Rudbeckia triloba is commonly cultivated in flower and butterfly gardens. Like other species of Rudbeckia, its various parts have been used in diuretic teas, as anti-inflammatory agents and as painkillers. (Moerman, 1998.) The chemical compound Coumarin is naturally transformed into an anticoagulant by a series of reactions with fungi, and is then used in pharmaceutical anticoagulants like Coumadin. (Gutierrez & Herz, 1990.)