Black-eyed Susan (Rudbeckia hirta) is a vibrant, hardy flowering plant in the daisy family (Asteraceae), beloved by gardeners and wildflower enthusiasts alike across North America and beyond. With its bold golden-yellow petals radiating outward from a striking dark brown to nearly black central cone, this cheerful wildflower has become an iconic symbol of late-summer meadows and cottage gardens.
• Native to North America and now naturalized across much of the continent
• State flower of Maryland, designated in 1918
• Belongs to the large genus Rudbeckia, which honors Olaus Rudbeck, a 17th-century Swedish botanist
• The species epithet "hirta" is Latin for "hairy," referring to the coarse trichomes (hair-like structures) covering its stems and leaves
• Widely used in prairie restoration, pollinator gardens, and as a cut flower
• A member of the Asteraceae, one of the largest and most successful flowering plant families with over 32,000 species worldwide
Taxonomie
• Originally a prairie and open woodland species of central North America
• Has been introduced and naturalized across all 48 contiguous U.S. states, much of Canada, and parts of Europe, Asia, and other continents
• Thrives in disturbed habitats, roadsides, meadows, and open woodlands
• The genus Rudbeckia comprises approximately 25 species, nearly all native to North America
• Black-eyed Susan has been cultivated in European gardens since at least the early 17th century, making it one of the first North American wildflowers to gain popularity abroad
• Several cultivated varieties and cultivars have been developed, including the popular 'Indian Summer,' 'Goldsturm,' and 'Toto' series, which have earned Royal Horticultural Society Awards of Garden Merit
Stems & Leaves:
• Stems are erect, stout, and prominently covered in coarse, stiff hairs (trichomes), giving them a rough texture
• Basal leaves are broadly lanceolate to ovate, 5–17 cm long, with coarsely toothed to entire margins
• Stem leaves are alternate, sessile, and progressively smaller toward the apex
• All leaves are dark green and densely pubescent (hairy) on both surfaces
Flower Heads:
• Composite flower heads (capitula) are 5–8 cm in diameter, borne singly on long peduncles
• Ray florets: 8–21 per head, golden yellow to orange-yellow, strap-shaped, 2–4 cm long
• Disc florets: densely packed in a raised, dome-shaped central cone, dark brown to purplish-black — the characteristic "black eye"
• The central cone is composed of hundreds of tiny tubular florets that mature from the outside inward
• Blooms from June through October, providing extended seasonal color
Fruit & Seeds:
• Fruit is a small, dry, one-seeded achene (~1.5–2 mm long), dark gray to black
• Each flower head can produce hundreds of seeds
• Seeds are an important food source for goldfinches and other songbirds
• Seeds lack a pappus (unlike many Asteraceae), so dispersal is primarily by gravity and animals rather than wind
Habitat:
• Open prairies, meadows, savannas, and roadsides
• Open woodlands and forest edges
• Disturbed areas, abandoned fields, and roadsides
• Tolerates a wide range of soil types, including clay, loam, and sandy soils
Pollinator Support:
• Attracts a diverse array of pollinators including native bees, honeybees, butterflies, hoverflies, and beetles
• Particularly valued by specialist bees in the genus Andrena
• Serves as a larval host plant for the bordered patch butterfly (Chlosyne lacinia) and the gorgone checkerspot (Chlosyne gorgone)
Wildlife Value:
• Seeds are a favored food of American goldfinches, chickadees, and other granivorous birds
• Foliage is browsed by deer and rabbits, though the coarse hairs provide some deterrence
• Provides late-season nectar when many other wildflowers have finished blooming
Soil & Drought Tolerance:
• Deep taproot system provides excellent drought tolerance once established
• Tolerates poor, dry, and compacted soils
• USDA Hardiness Zones 3–9
• Thrives in full sun (minimum 6 hours direct sunlight per day)
• Contains compounds that can cause gastrointestinal upset (vomiting, diarrhea) in pets
• The plant's coarse hairs may cause mild skin irritation in sensitive individuals
• Not considered toxic to humans, though it is not consumed as a food plant
• Gardeners with sensitive skin may wish to wear gloves when handling the plant extensively
Light:
• Full sun (6+ hours of direct sunlight per day) for best flowering
• Tolerates light shade but will produce fewer blooms and may become leggy
Soil:
• Adaptable to a wide range of soil types — clay, loam, sandy, or rocky
• Prefers well-drained soil but tolerates occasional wet conditions
• pH range: 5.5–7.5 (slightly acidic to neutral)
• Does not require rich soil; excessive fertility can lead to floppy growth
Watering:
• Drought-tolerant once established; water regularly during the first growing season
• Mature plants typically need supplemental watering only during prolonged dry spells
• Avoid overwatering, which can lead to root rot
Temperature:
• USDA Hardiness Zones 3–9
• Tolerates summer heat and humidity as well as winter cold down to approximately -40°C (Zone 3)
Propagation:
• Seed: sow directly outdoors in fall or early spring; seeds benefit from cold stratification (2–4 weeks at 1–5°C) for improved germination
• Division: divide established clumps in early spring every 3–4 years to maintain vigor
• Self-seeds readily; deadheading prolongs bloom time but reduces self-sowing
Common Problems:
• Powdery mildew — especially in humid conditions with poor air circulation
• Leaf spot diseases (Septoria, Alternaria) — remove affected foliage
• Aster yellows — a phytoplasma disease spread by leafhoppers; infected plants should be removed and destroyed
• Slugs and snails may damage young seedlings
• Japanese beetles may feed on foliage and flowers
Traditional & Herbal Medicine:
• Native American tribes, including the Ojibwe and Cherokee, used root preparations as a treatment for colds, earaches, and snakebites
• Root infusions were traditionally used as a diuretic and immune system tonic
• Some research has identified immunostimulant properties in Rudbeckia extracts, though clinical evidence remains limited
Horticultural Uses:
• Widely used in perennial borders, cottage gardens, and naturalistic plantings
• Excellent for prairie and meadow restoration projects
• Popular as a long-lasting cut flower in floral arrangements
• Used in rain gardens and bioswales due to tolerance of variable moisture conditions
Ecological Uses:
• Important component of pollinator habitat restoration
• Used in erosion control plantings on slopes and disturbed sites
• Provides critical late-summer and fall nectar resources for migrating butterflies
Anecdote
The common name "Black-eyed Susan" originates from an 18th-century English ballad by John Gay, in which a woman named Susan searches the fields for her lover, William, who is described as having "black eyes." The flower's dark central cone and bright golden petals were seen as a perfect match for the poem's imagery, and the name stuck. Rudbeckia hirta holds the distinction of being the first state flower of Maryland, adopted in 1918 — decades before most other states chose their floral emblems. The flower's black-and-gold color scheme also matches the state's official colors, derived from the coat of arms of the Calvert family, the colonial proprietors of Maryland. The "black eye" of the flower is not a single structure but a dome composed of hundreds of tiny individual disc florets. Each floret opens sequentially from the outer edge of the cone toward the center over a period of several days, creating a mesmerizing spiral pattern that follows the mathematical Fibonacci sequence — a phenomenon shared with sunflowers, pinecones, and many other members of the Asteraceae family. Black-eyed Susan is a champion self-seeder. A single plant can produce over 1,000 seeds per flower head, and a robust multi-headed plant may release tens of thousands of seeds in a single season. These seeds can remain viable in the soil seed bank for several years, ensuring the species' persistence even after unfavorable growing conditions. In the language of flowers (floriography), popular during the Victorian era, Black-eyed Susan symbolizes "justice" — a meaning that has endured in floral symbolism to the present day.
En savoir plus
