Introduction

Black-eyed Susan forms a clumping, 2-foot-tall mound of foliage topped with a bright display of red/orange flowers bordered with yellow (Figure 1). Distribution of color in the flower varies depending on the cultivar and seed source. Flowering is more profuse when the faded blossoms are regularly removed. The flowers are useful for cutting. Space plants 18 to 24 inches apart in a mass planting to create a carpet of color. Plants can become weeds in the garden because seeds germinate readily in nearby beds. What a wonderful weed to have in the garden!

General Information

Scientific name: Rudbeckia hirta

Pronunciation: rudd-BECK-kee-uh HER-tuh

Common name(s): black-eyed Susan, gloriosa daisy, coneflower

Family: Compositae

Plant type: annual; perennial; biennial; herbaceous

USDA hardiness zones: 2 through 11 (Figure 2)

Planting month for zone 7: Jun; Jul

Planting month for zone 8: May; Jun

Planting month for zone 9: Apr; May

Planting month for zone 10 and 11: Mar; Apr; Oct; Nov

Origin: native to North America

Uses: mass planting; border; cut flowers

Availability: generally available in many areas within its hardiness range

Description

Height: 2 to 3 feet

Spread: 2 to 3 feet

Plant habit: spreading; round

Plant density: open

Growth rate: moderate

Texture: medium

Foliage

Leaf arrangement: alternate

Leaf type: simple

Leaf margin: entire

Leaf shape: ovate

Leaf venation: none, or difficult to see

Leaf type and persistence: deciduous

Leaf blade length: 4 to 8 inches

Leaf color: green

Fall color: not applicable

Fall characteristic: not applicable

Flower

Flower color: orange-red; yellow

Flower characteristic: summer flowering; fall flowering

Fruit

Fruit shape: no fruit

Fruit length: no fruit

Fruit cover: no fruit

Fruit color: not applicable

Fruit characteristic: inconspicuous and not showy

Trunk and Branches

Trunk/bark/branches: not applicable

Current year stem/twig color: green

Current year stem/twig thickness: medium

Culture

Light requirement: plant grows in full sun

Soil tolerances: clay; sand; acidic; loam

Drought tolerance: high

Soil salt tolerances: good

Plant spacing: 12 to 18 inches

Other

Roots: not applicable

Winter interest: not applicable

Outstanding plant: not particularly outstanding

Invasive potential: may self-seed each year

Pest resistance: long-term health usually not affected by pests

Use and Management

The many Rudbeckia species tolerate most well-drained soils if given full sun. Provide excellent drainage for best growth. High salt tolerance makes Rudbeckia well-suited for planting close to the beach.

Various flower color combinations of red, orange, and yellow are available in the five or more available cultivars. Rudbeckia hirta 'Indian Summer' is a sturdy selection with large, yellow flowers that develop 10 to 14 weeks after seeds are sown. Unlike many other black-eyed Susans, this one does not require staking. It is also relatively free of disease and insect problems.

Rudbeckia seed may be planted directly into the garden. The seed germinates in 5 to 10 days at temperatures between 70°F to 75°F. Seed started indoors germinates more quickly. Barely cover the seed. The plants wilt for one or two days after transplanting. Propagate perennial types by division. Rudbeckia is generally propagated in the garden by division or cuttings in the spring or fall season.

Pests and Diseases

Aphids suck sap from the plants and coat the leaves with sticky honeydew.

Goldenglow sawfly may completely defoliate plants. The larvae are gray with dark stripes.

Four-lined plant bug causes round, brown, sunken spots on the leaves. The injury is often mistaken for a disease.

Downy mildew causes seedlings to wilt and die. On older plants the foliage is mottled light yellow.

Several leaf spots may be found but are not serious. Remove and destroy infected leaves.

Powdery mildew may cause a white, powdery growth on the leaves in late summer.

White smut causes light spots on the leaves. Destroy plant residues in the fall and get rid of infected plants as you notice them.

Verticillium wilt may kill Rudbeckia spp.