|Rudbeckia hirta flowerhead|
Rudbeckia hirta, black-eyed Susan, is a species of flowering plant in the family Asteraceae, native to the central United States. It is one of a number of plants with the common name black-eyed Susan. Other common names for this plant include: brown-eyed Susan, brown Betty, gloriosa daisy, golden Jerusalem, Poorland daisy, yellow daisy, and yellow ox-eye daisy.
It is an upright annual (sometimes biennial or perennial) growing 30–100 cm (12–39 in) tall by 30–45 cm (12–18 in) wide. It has alternate, mostly basal leaves 10–18 cm long, covered by coarse hair, with stout branching stems and daisy-like, composite flowers appearing in late summer and early autumn. In the species, the flowers are up to 10 cm (4 in) in diameter, with yellow ray-florets circling conspicuous brown or black, dome-shaped disc-florets. However, extensive breeding has produced a range of sizes and colours, including oranges, reds and browns.
The genus name honors Olaus Rudbeck, who was a professor of botany at the University of Uppsala in Sweden and was one of Linnaeus's teachers. The specific epithet refers to the trichomes (hairs) occurring on leaves and stems.
There are four varieties:
- Rudbeckia hirta var. angustifolia. Southeastern United States (South Carolina to Texas).
- Rudbeckia hirta var. floridana. Florida, endemic.
- Rudbeckia hirta var. hirta. Northeastern United States (Maine to Alabama).
- Rudbeckia hirta var. pulcherrima. Widespread in most of North America (Newfoundland to British Columbia, south to Alabama and New Mexico; naturalized Washington to California).
R. hirta is widely cultivated in parks and gardens, for summer bedding schemes, borders, containers, wildflower gardens, prairie-style plantings and cut flowers. Numerous cultivars have been developed, of which 'Indian Summer' and 'Toto' have gained the Royal Horticultural Society's Award of Garden Merit. Other popular cultivars include 'Double Gold' and 'Marmalade'.
Symbolism and uses 
The black-eyed Susan was designated the state flower of Maryland in 1918. The Preakness Stakes in Baltimore, Maryland has been termed "The Run for the Black-Eyed Susans" because a blanket of chrysanthemums, decorated to look like black-eyed Susans, is traditionally placed around the winner's neck (actual black-eyed Susans are not in season during the Preakness).
The black-eyed Susan which means “Justice” makes a very nice cut-flower with a vase life up to 10 days.
Butterflies are attracted to Rudbeckia hirta when planted in large color-masses.
Traditional medicine 
The roots but not seedheads of Rudbeckia hirta can be used much like the related Echinacea purpurea. It is an astringent used as in a warm infusion as a wash for sores and swellings. The Ojibwa used it as a poultice for snake bites and to make an infusion for treating colds and worms in children. The plant is diuretic and was used by the Menominee and Potawatomi. Juice from the roots had been used as drops for earaches.
- Floridata: Rudbeckia hirta.
- RHS A-Z encyclopedia of garden plants. United Kingdom: Dorling Kindersley. 2008. p. 1136. ISBN 1405332964.
- Andy's Northern Ontario Wildflowers: Native Meadow Wildflowers. Black-eyed Susan.
- "Fiscal and Policy Notes (HB 345)". Department of Legislative Services - Maryland General Assembly. 2010. Retrieved 2010-03-13.
- "Black Eyes Susan Wildflower".
- Schillo, Rebecca (2011). "Native Landscaping Takes Root in Chicago". In Cummings, Nina. In The Field: 13.
- Black-Eyed Susan
- Rudbeckia hirta
- Moerman. D. Native American Ethnobotany Timber Press. Oregon. 1998 ISBN 0-88192-453-9
|Wikimedia Commons has media related to: Rudbeckia hirta|
|Wikiversity has bloom time data for Rudbeckia hirta on the Bloom Clock|
- Germplasm Resources Information Network: Rudbeckia hirta
- USDA Plant Profile: Rudbeckia hirta
- Rudbeckia hirta Large format diagnostic photographs
- A Tale of Two Susans non-scholarly essay on the etymology and history
- Knowlton Foote. 2001. Black-eyed Susan (Rudbeckia hirta L.). New York Flora Association. Newsletter Vol. 13.