Rudbeckia hirta was first described by Linnaeus in 1753 in Species Plantarum. In 1904, O.A. Farwell described the variety pulcherrima in the Annual Report of the Michigan Academy of Science. Then, in 1957, R. Perdue, Jr., published "Synopsis of Rudbeckia Subgenus Rudbeckia" in which the four recognized varieties included hirta, pulcherrima, angustifolia and floridana.
Rudbeckia hirta var. hirta is classified as an endangered plant in the State of New York. (USDA, 2010.)
Legislation of 1918 designated Rudbeckia hirta the state flower of Maryland. Also, the Highway Beautification Act of 1965 has led to a cascade of similar legislations requiring funding for the planting of native wildflowers along highways. This has undoubtedly influenced populations of Rudbeckia hirta and similar native wildflowers.
A 2005 study identified three different chromosome types in Rudbeckia hirta, with a chromosome number of 2n=36. Its karyotype is considered to be asymmetric and evolved. (Cimpeanu, M., C. Cimpeanu, Capraru & Costeea, 2005.)
Although naturally diploid, polyploidy has been exploited in the cultivation of Rudbeckia hirta. The tetraploid cultivar of var. pulcherrima, commonly known as the Gloriosa daisy, has a drastically shortened lifespan as a tradeoff for its almost double-sized flowerheads. (Cullina, 2000.)
Rudbeckia hirta has a moderate growth rate.
Rudbeckia hirta and Thelesperma filfolium have very similar flower heads, but can be distinguished by differences in foliage. R. hirta is also commonly confused with its cousin, R. fulgida.
Rudbeckia hirta is associated with a variety of insects. Many species of bees are pollinators, feeding on nectar. Some caterpillars chew on the leaves and Blackberry loopers (moths) feed on the petals. A few species of flies tend to stay close to the flowers, and goldfinches may eat the seeds. R. hirta is especially susceptible to powdery mildew. Cultivars of R. hirta have been hybridized with cultivars of R. Laciniata (Al-Atabee, Mulligan & Power, 1990.), and many of the types commonly used in cultivation are, in fact, hybrids. 'Kelvedon star', 'Gloriosa' and 'Irish eyes' are a few of the more popular cultivars.
Rudbeckia hirta spans the entire U.S., except Arizona and Montana, and the southern reaches of Canada. Var. pulcherrima can be found throughout this entire range, but the other varietal populations are localized. Var. floridana is isolated in southern Florida, while var. angustifolia grows through the entire Gulf Coastal plain. Var. hirta is mostly found from the Appalachians to Illinois, but it can be found along the entire U.S. Atlantic coast. (Urbatsch & Cox, 2006.)
For more information, see the map provided by Flora of North America.
All varieties of R. hirta can be found in open spaces such as meadows, roadsides and fields, and open woody areas.
Annuals, biennials and perennials. Vars. angustifolia and floridana are known to undergo all three life cycles. Var. hirta is biennial or perennial, and var. pulcherrima is annual or perennial. (Urbatsch & Cox, 2006.)
One to several years. Many hybrids have a shortened life cycle, lasting a year or less.
Vars. floridana, hirta and pulcherrima can be found in bloom from spring to fall, but var. angustifolia has a shorter flowering period lasting from spring to summer. (Urbatsch & Cox, 2006.) Studies show that several factors including climate warming and day length can induce or delay the flowering cycle. Increasing temperature seems to be correlated with an earlier onset of blooming. (Bradley, Leopold, Ross & Huffaker, 1999.) If day length never increased in the spring, Rudbeckia hirta would never grow beyond its rosette, therefore never producing flowers. (Harkess & Lyons, 1994.)
According to a 1998 publication by the Southern Weed Science Society, this plant can be weedy and invasive. (USDA, 2010.)
Rudbeckia hirta is, first and foremost, an attractive flower commonly used in gardening. The Potawatomi use the roots in a tea to treat colds, and the ray flowers in yellow dye. The leaves are gaining notoriety as they contain a stimulant, often used in teas as diuretics.