Rudbeckia, commonly known as Black-eyed Susans, Gloriosa Daisies, or Coneflowers, are a genus of flowering plants in the Asteraceae family. Rudbeckia flowers feature a prominent, raised central disc in black, brown shades of green, and in-between tones. All are native to North America, and many species are cultivated in gardens for their showy yellow or gold flower heads that bloom in mid to late summer, the flower has become naturalized in Zones 3 to 9.
Rudbeckia is one of at least four genera within the flowering plant family Asteraceae whose members are commonly known as coneflowers; the others are Echinacea, Dracopis, and Ratibida. Rudbeckia species are eaten by the caterpillars of some Lepidoptera species including cabbage moths and dot moths.
At maturity, the plant reaches heights of up to 3 feet. Black-eyed Susan is suitable for U.S. Department of Agriculture plant hardiness zones 2 through 11. Although black-eyed Susan is a moderately drought-tolerant plant, the soil should never be bone dry. Water only when the top of the soil feels dry, as Black-eyed Susan is prone to rot in muddy soil. To produce long, healthy roots, provide enough water to soak the roots. Water the soil at the base of the plant, as overhead watering puts the plant at risk for mildew and other moisture-related diseases.
Key characteristics of Rudbeckia
- Growth Habit: Herbaceous plants that can be annual, biennial, or perennial, depending on the species.
- Height: Ranges from 1 to 9 feet (30 cm to 2.7 meters), depending on the variety.
- Flowers: Bright yellow, orange, or gold ray florets with dark brown or black central discs, forming daisy-like blooms.
- Bloom Time: Long blooming period, typically from summer to early fall.
- Leaves: Rough-textured, lance-shaped, or slightly lobed, medium to dark green in color.
- Sunlight Requirements: Thrives in full sun but can tolerate partial shade.
- Soil Preferences: Adaptable to a variety of soil types, prefers well-drained soil.
- Wildlife Benefits: Attracts pollinators like bees and butterflies; seeds are a food source for birds.
- Hardiness: Hardy in USDA zones 3–9, with good tolerance for drought and heat once established.
Cultivation
- Plant Rudbeckia in a spot that receives full sun for at least 6 hours daily. Partial shade is acceptable but may reduce flowering.
- Use well-drained soil enriched with compost or organic matter. Rudbeckia is adaptable but prefers slightly acidic to neutral soil (pH 6.0–7.5).
- Sow seeds directly in the garden after the last frost or start indoors 6–8 weeks before the frost date. For transplants, plant in spring or early fall.
- Water regularly to establish young plants. Once mature, Rudbeckia is drought-tolerant but benefits from consistent moisture during dry spells.
- Apply a balanced, slow-release fertilizer in spring to encourage healthy growth. Avoid over-fertilizing, as it can lead to fewer blooms.
- Add a 2–3 inch (5–8 cm) layer of mulch around the base to retain moisture, regulate soil temperature, and suppress weeds.
- Remove spent flowers to encourage continuous blooming and prevent excessive self-seeding.
- Cut back foliage in late fall or early spring to clean up the plant. Divide perennials every 3–4 years to maintain vigor and prevent overcrowding.
- Rudbeckia is relatively pest-resistant but can occasionally face issues like powdery mildew or leaf spots. Provide good air circulation and avoid overhead watering.
- In colder climates, leave some seed heads for winter interest and as food for birds. Mulch perennials in late fall for added protection against harsh weather.
Notable Species of Rudbeckia
Rudbeckia hirta
- Common Name: Black-eyed Susan
- Characteristics: Known for its bright yellow petals with a dark brown or black central cone. Often grown as an annual or biennial.
- Uses: Popular in wildflower meadows and garden borders.
Rudbeckia fulgida
- Common Name: Orange Coneflower
- Characteristics: A hardy perennial with golden-yellow petals and a dark center. Most notable cultivar: Rudbeckia fulgida var. sullivantii ‘Goldsturm’.
- Uses: Ideal for mass plantings and perennial borders.
Rudbeckia laciniata
- Common Name: Cutleaf Coneflower
- Characteristics: Tall species (up to 9 feet), featuring deeply lobed leaves and pale yellow flowers with a greenish cone.
- Uses: Suited for naturalized areas and back-of-the-border plantings.
Rudbeckia triloba
- Common Name: Brown-eyed Susan
- Characteristics: Smaller flowers compared to other species, with multiple blooms per stem and a bushy appearance.
- Uses: Great for cottage gardens and informal plantings.
Rudbeckia maxima
- Common Name: Giant Coneflower
- Characteristics: Large blue-green basal leaves and tall stems with yellow flowers and a prominent central cone.
- Uses: Perfect for dramatic accents in large gardens.
Rudbeckia nitida
- Common Name: Shiny Coneflower
- Characteristics: Glossy green leaves and tall stems with yellow flowers and drooping petals.
- Uses: Works well in moist or wet soils, often in naturalized settings.
Rudbeckia occidentalis
- Common Name: Western Coneflower or Black Coneflower
- Characteristics: Unique appearance with no ray petals, only a prominent dark cone.
- Uses: Adds architectural interest to the garden.
Rudbeckia subtomentosa
- Common Name: Sweet Coneflower
- Characteristics: Fragrant, yellow flowers with a chocolate-brown center. A robust perennial.
- Uses: Excellent for pollinator gardens and wildflower meadows.
Rudbeckia texana
- Common Name: Texas Coneflower
- Characteristics: Native to Texas and surrounding areas, with narrow leaves and yellow flowers.
- Uses: Thrives in hot, dry climates.
Rudbeckia mollis
- Common Name: Soft Coneflower
- Characteristics: Fuzzy leaves and stems with light yellow flowers and a softer texture compared to other species.
- Uses: Suited for naturalized gardens and pollinator habitats.