By Julie Christensen
Black-eyed Susans (Rudbeckia hirta), also known as coneflowers or Gloriosa daisies, make up a family of about 30 species of flowers, all native to North America. These plants grow wild in woodland areas and fields, and tolerate a wide variety of growing conditions. They’re prized in the garden for their bright yellow-orange, daisy-like flowers with the characteristic brown or black middle. The flowers also make fine cutting flowers and attract butterflies and birds to the garden.
Black-eyed Susans are short-lived perennials, annuals or biennials, depending on the climate and variety. Perennial varieties are usually hardy in U.S.D.A. plant hardiness zones 4 through 7. When left to their own devices, the plants self-sow prolifically, and will likely return even if they grow as annuals in your area.
Black-eyed Susans are usually started as nursery transplants, but you can also grow them from seed. The seeds need a period of moist cold, known as stratification, to break dormancy and germinate. To achieve this, you can either sow them outdoors in the fall or store them indoors in a refrigerator. If storing indoors, place the seeds in a baggie with 1 tablespoon of moistened potting mix and put them in the refrigerator for 12 weeks prior to sowing. Sow seeds indoors 8 weeks before the last expected frost. Place seeds in a light starting mix and cover them with 1/16 inch of soil. Keep the soil slightly moist and warm. Seeds germinate in 12 to 30 days at 70 degrees Fahrenheit.
If you’d like to save seeds, allow the heads to ripen from green to brown or black. Inside these heads lie thousands of seeds. Leave the heads intact on the plants for several weeks after the flowers fade, or until the heads darken and start to fall apart. Cut the heads off and break them open. Shake out the seeds onto a cookie tray and allow them to dry out thoroughly for several weeks. Place the seeds in a labeled bag and store them in the refrigerator or plant them directly in the garden in the fall.
Plant black-eyed Susans in full sun to partial shade. They’re not particular about soil type or fertility, although the soil must be well-draining. Keep the soil evenly moist while the plants become established. Space the plants at least 12 to 18 inches apart, so air circulates freely. Most black-eyed Susans grow between 2 and 3 feet tall and wide, although some have a compact or even vining habit.
Black Eyed Susan Flower Growing Tips
There’s not much to growing black-eyed Susans. Water them weekly during dry weather and fertilize them with a liquid all-purpose fertilizer if growth wanes or the leaves appear pale. The plants are subject to rust and mildew, but the damage is rarely serious. To prevent these diseases, space plants far enough apart so they’re not crowded. Avoid using overhead sprinklers, which can promote disease, and opt for drip systems and soaker hoses instead. Remove any diseased plant parts and destroy them.
Deadhead plants to promote more blossoms and cut them back midsummer if they start to become straggly. Shearing them will encourage compact growth and more blooms. Black-eyed Susans bloom from early summer to fall.
Traditional black-eyed Susans are charming, but several new varieties are worth your attention. ‘Irish Eyes’ has lovely green cones instead of the more common brown or black, while ‘Bambi’ has flowers that range in color from pale yellow to red and brown. ‘Toto’ is a compact variety ideal for container culture. It grows only 12 inches tall. ‘Indian summer’ is prized for its large, yellow flowers, which can span 9 inches across.
In addition to these varieties, consider related species. Try giant coneflower (Rudbeckia maxima) a very large variety that grows up to 6 feet tall. ‘Goldsturm’ (Rudbeckia fulgida var. sullivantii ‘Goldsturm’) is a long-blooming, perennial variety.
For more information, visit the following links:
Black-eyed Susan from Colorado State University Extension
Coneflowers, Black-eyed Susans from the University of Kentucky Cooperative Extension Program
When she’s not writing about gardening, food and canning, Julie Christensen enjoys spending time in her gardens, which include perennials, vegetables and fruit trees. She’s written hundreds of gardening articles for the Gardening Channel, Garden Guides and San Francisco Gate, as well as several e-books.