Rudbeckia–commonly called black-eyed Susan or gloriosa daisy–produces golden daisy-like, brown-centered blooms from late summer to fall. Black-eyed Susans are tough and easy to grow.
The Rudbeckia genus is made up of about 20 annuals, biennials, and perennials. Garden Rudbeckias are descendants of North American wildflowers.
Rudbeckias thrive in all but soggy soils. They are drought-tolerant once established.
Rudbeckia are probably the brightest bloomers in the late summer and fall garden. They are well suited for perennial borders. Faded flower heads can remain for winter interest in the garden.
Get to Know Rudbeckia
- Plant type: Perennial, some grown as annuals
- Growing Zones and range: Zones 3 to 10
- Hardiness: Hardy to -35°F (-37°C); hardy
- in both cold and hot weather
- Height and width: 8 inches (20cm) to 4 feet (1.2m) tall; 2 to 4 feet wide, depending on the variety
- Foliage: Prominently veined, toothed toward the end
- Flowers: Golden daisy-like ray flowers around a dark brown central disc; petals of some cultivars are orange, pale yellow, bronze, or just, sometimes bicolored; flowers can be up to 6 inches (15cm) wide
- Flower colors: Yellow, orange, gold, mahogany, red, and bicolors, sometimes bicolored
- Bloom time: Summer into fall; flower continue through autumn in Zones 9-11
- Uses: Mixed border, cottage garden, cut flowers
- Garden companions: ornamental grasses, sedums, blazing star, Joe-pye weed, asters
- Common name: Black-eyed Susan, coneflower
- Botanical name: Rudbeckia spp.
- Family: Asteraceae
- Origin: North America
Where to Plant Rudbeckia
- Plant Rudbeckia in full sun.
- Rudbeckia grows best in humus-rich to average soil. It will tolerate clay soil.
- Rudbeckia prefers a soil pH of 6 to 7.
Rudbeckia Uses and Companions
- Grow Rudbeckia in a border, massed for effect.
- Neutralize Rudbeckia in a meadow or woodland garden.
- Most cultivars of Rudbeckia hirta are grown as annuals and are used as bedding or in borders.
- Flower last well when cut, and cutting promoters continued bloom.
- Good garden companions for Rudbeckia include Achillea, Artemisia, Echinacea purpurea, Echinops, Helenium, Gaillardia grandiflora, Nepeta, Salvia, Sisyrinchium striatum, ornamental grasses.
When to Plant Black-Eyed Susan
- Set perennial Rudbeckia in the garden in spring or fall after hardening them off. Set plants outdoors when temperatures average 65°F (18°C) or greater.
- Start seed indoors 3 to 4 weeks before the last frost in spring. Plants grown from seeds planted in early spring will bloom the same year. Late started plants will bloom the next year.
- Start seed outdoors in evenly prepared soil after the lasts spring frost or sow seed outdoors in fall in Zones 9 and 10.
Planting and Spacing Rudbeckia
- Indoors, sow seed in six-packs or flats filled with moist, sterile seed starting medium. Sow seed at 70°F (21°C). Do not cover seeds, just pat them into the soil.
- Germination takes about 14 days under bright light.
- Thin seedlings when they are 3 inches (7.5cm) tall or more; pot up seedlings to individual pots.
- Space Rudbeckia 2 feet apart.
How to Water and Feed Rudbeckia
- Rudbeckia grows best with abundant moisture; keep the soil evenly moist. Established Rudbeckia will tolerate drought.
- Fertilize Rudbeckia lightly at planting time and in midsummer.
- Mulch around Rudbeckia to conserve soil moisture.
- Rudbeckia does not require fertilizer.
- Stake tall plants to keep them from flopping.
- Trim spent blooms to promote longer flowering.
- Rudbeckia is susceptible to powdery mildew.
Rudbeckia Pests and Diseases
- Sawfly and aphid may attack Rudbeckia. Treat with insecticidal soap.
- Downy mildew may be prevented by good air circulation.
- Propagate Rudbeckia by seed or division.
- Seeds germinate in 14 days sown outdoors after the last frost.
- Seeds germinate in 5 to 7 days at 68° to 72°F (22°C).
- Divide large clumps when new leaves grow in early spring. Separate every other plant. Replant divisions immediately. Spring divide plants should bloom the same year.
Rudbeckia Varieties to Grow
- Rudbeckia fulgida: Perennial black-eyed Susan has an orange coneflower. ‘Goldstrum’ is a cultivar that is hardy in Zones 3-9; grows to 24 inches (61cm) with flowers to 5 inches (12.7cm) wide.
- R. hirta, Gloriosa daisy: Short-lived perennial usually grown as an annual; grows 18 to 24 inches (45-61cm) tall; broad daisy-like flowers in yellow to orange and can be bicolored or striped; several cultivars; easy to grow from seed.
- R. laciniata ‘Gold Drop’: Grows to 24 inches (61cm) tall or greater; pale yellow double flower on wiry stems.
- R. maxima, giant coneflower: Grows 5 to 9 feet (2.7m) tall; bears 3- to 5-inch flowers with orange-yellow ray florets and cone-shaped brown centers.
- R. nitida, shining coneflower: Perennial in Zones 4-10; it grows to 4 feet (1.2m) tall.