Rudbeckia
Family Asteraceae
Genus Rudbeckia
Introduction
This great wildflower of North America is among the famous group of wildflowers that inhabit the prairies. The Black Eyed Susans were the first to become domesticated garden flowers. The genus was classified by Linnaeus who chose to name it in honor of his mentor and friend, Olof Rudbeck (1660-1740). There are over 30 species native to America. This species is found in moist meadows of Michigan, south to Missouri and West Virginia. The species was classified by English botanist William Aiton (1731-1793). "Goldsturm" is an old German seed strain that has proven far better under cultivation although it is hotly debated whether there is a difference between R.F. var sullivantii and Goldsturm.
Special Features
Coneflowers are prolific bloomers from early summer to frost and are the backbone of many perennial gardens. These natives of North American grasslands and meadows have daisy like flower heads with intense yellow rays that contrast to their centers of deep brown. Coneflowers have large, hairy leaves and stiff stems. Showy flowers brighten summer and fall beds. They are good cut flowers that will rebloom late in season after earlier cutting. They are excellent in sunny borders, mixed with clumps of ornamental grasses, or naturalized in meadows. Flowers can be single or double petaled, and range in color from Bright yellow to mahogany with every shade in between. Some species, like Pinwheel, will have more then one color flower on a single plant.
Hardiness
Zone hardiness varies by species, but can be grown from zone 3 to zone 9. Depending on species, Rudbeckia are perennial, biennial or short-lived perennial. It is often grown as an annual.
Growth Habit
Some species of Rudbeckia are low growing at 8 to 10 inches. Others form an upright clumping mound with branching stems that range in height from 2 to 7 feet. Spread can be as small as 12 inches wide to one large continuous spreading clump.
Bloom Time
Rudbeckia have a long blooming period from early summer to frost. This makes them an invaluable addition to the late summer garden. Dead-heading or cutting back will encourage the plant to re-bloom later in the season.
Propagation
Divide clumps when they become too crowded, usually every few years. Division should be done in early spring or autumn.
Germination
Seeds sown in containers should not be planted too deeply. Seeds will germinate in approximately 20 days at 70° F. Coneflowers take up to 20 weeks to flower when started from seed.
Transplanting
Seedlings grown from seeds can be transplanted in seven days. Rudbeckia transplants well if kept moist until re-established. When transplanting large clumps divide before replanting.
Soil
Rudbeckia will thrive in all but soggy soil. Some species prefer soil that is fertile and moist while others will grow in drier soil. All prefer well-drained soil.
Irrigation
Rudbeckia are not moisture lovers therefore making them an ideal plant for xeriscaping. They will hold up well during periods of drought with little watering.
Sunlight
Rudbeckia like full sun and thrive when planted where they can get full sun all day.
Pests
Rudbeckia are bothered by the following pest: Asiatic garden beetle, crescent marked lily aphid, flea hopper, four lined plant bug, Fuller rose beetle, sawflies, stalk borer, two spotted spider mites and white flies.
Disease
Rudbeckia are susceptible to downy mildew, powdery mildew, rust, stem rot, wilt, Aster yellow, and leaf spot (Alternaria, Cercospora, Colletotrichum, Phyllosticta or Septoria spp.).
References
The Southern Living Garden Book by Oxmoor House
Perennials A Dorling Kindersley Book
Plant Propagation by American Horticultural Society
The Plant & Pest Diagnostic Laboratory at Purdue University
Plant & Pest Handbook from the Connecticut Agricultural Experiment Station