766 Rudbeckia hirtaCommon Names: black-eyed Susan, gloriosa daisy, yellow oxeye daisy Family: Asteraceae (aster/daisy Family)
Everyone's favorite summertime flower is the black-eyed Susan, sometimes an annual, sometimes a perennial, and sometimes a biennial (flowering in its second year, then dying). This is a member of the huge aster or composite family, and has the typical daisylike flowerheads consisting of an outer ring of ray florets and a central receptacle composed of many disk florets. Black-eyed Susans typically stay in a basal rosette their first year, and then produce upright branching stems with flowers in their second year. The rough-textured basal leaves are diamond shaped, 4-7 in (10-18 cm) long, and have three conspicuous veins. When she's ready, black-eyed Susan produces erect, bristly stems to 3 ft (0.9 m) tall, which branch freely and bear hairy lance shaped leaves, 2-3 in (5-7.6 cm) long.
Some forms of black-eyed Susan are true annuals and some are true perennials, though. The flowerheads in the wild form are up to 3 in (7.6 cm) across and produced abundantly throughout the summer until mid-autumn. The 10-20 rays are usually yellow or golden and the receptacle is purplish brown and often distinctly conical. There are many garden cultivars. 'Supurba' has ray flowers that are yellow on top and maroon beneath. 'Bambi' is small, to 12 in (30.5 cm), with chestnut colored ray flowers. 'Irish Eyes' has bright yellow rays and green disks. 'Toto' is dwarf and very compact, to 10 in (25 cm) tall, and ideal for edging or containers. The 'Gloriosa' and 'Double Gloriosa' cultivars have very large flowerheads, to 6 in (15 cm) across, with yellow, gold, chestnut or bronze rays. They are perennial, but bloom from seed in their first year. 'Gloriosa' daisies are tetraploids, with twice the normal number of chromosomes. They were created by treating normal plants with radiation or the DNA altering chemical, colchicine. Nevertheless, they come true from seed. 'Indian Summer', with golden yellow flowerheads 6-8 in (15-20 cm) across, and 'Goldilocks', with double flowers are probably tetraploids as well.
There are three regional varieties of Rudbeckia hirta, the wild black-eyed Susan, with one occurring naturally throughout much of North America from British Columbia to Newfoundland and south to Texas and Florida. The species is absent only from the Southwest. Black-eyes Susans grow in prairies, dry fields, open woods, along road shoulders and in disturbed areas.
CultureDeadhead spent flowers to prolong blooming. Light: Full sun to light shade. Moisture: Once established, black-eyed Susans are fairly drought tolerant, but they perform best with regular watering in soil that does not completely dry out. Hardiness: USDA Zones 3 - 10. Propagation: Sow seeds in place 2 weeks before the last expected frost or give them a head start indoors 6-8 weeks before setting out. The seeds need light to germinate, so just press them into the soil surface - don't bury them. Some of the cultivars are decidedly perennial, and these are best propagated by dividing the root mass during the dormant season.
Black-eyed Susan is at home in the naturalized, semi-wild garden, in borders and in flower beds. She won't complain if relegated to the cutting garden, either. Black-eyed Susan is a reliable summertime bloomer, providing bright splashes of color in a mixed perennial border or porch planter. Butterflies of many species are attracted to black-eyed Susan. But one of Susan's most influential uses is for resolving that age old lover's question: "... she loves me, she loves me not, she loves me, she loves me not, she loves me."
There are about 25 species of Rudbeckia, all native to North America. Orange coneflower (R. fulgida var. sullivantii) is another popular garden perennial. Purple coneflower (Echinacea purpurea) is closely related. The genus was named for the Swedish physician/botanist, Olaus Rudbeck (1660-1740), who preceded Carolus Linnaeus, the inventor of the binomial system of biological nomenclature, at the University of Upsala.
Steve Christman 8/18/00; updated 8/15/03, 6/17/04, 3/21/08