Black-eyed susan, Rudbeckia hirta

Life Cycle

Perennial or sometimes biennial

Propagation

Reproducing only by seed.

Stems

Stems are erect, 30 -100 cm high, single or with a few branches in the upper parts and more or less rough-hairy throughout.

Leaves

Leaves are alternate (1 per node) with the lower leaves long-elliptic, tapering to a long stalk (Figure 1-a). The upper leaves are narrow, stalkless, smooth-margined or somewhat coarsely toothed (Figure 1-b). All the leaves are rough-hairy and usually dark green.

Flowers and Fruit

Flower heads are large and showy at the ends of long, thin, erect branches, 2.5 -7.5 cm in diameter with ray florets (Figure 1-c) orange to orange-yellow and spreading like spokes of a wheel. The disk florets (Figure1-d) are dark purple or blackish, individually very small and tightly packed on a conic receptacle forming a prominent, hard, dark, raised centre in the head, like the hub of a wheel. The seeds are black, 4-angled with fine lengthwise lines. Flowers from mid-June to September.

Habitat

Black-eyed Susan is a native plant in the Great Plains but was introduced into Ontario and has spread aggressively throughout the province in meadows, pastures, edges of woods, river valleys, lakeshores and roadsides, usually in coarse-textured soils.

Distinguishing Features

It is distinguished by its long-elliptic, rough-hairy leaves, its showy, long-stemmed flower heads with bright orange to orange-yellow ray florets and dark purplish to blackish disk florets.


Figure #1.


Figure #2.


Figure #3.

Yellow-orange flower of black-eyed susan.


Figure #4.

Back of flower head.


Figure #5.

Hairy stem of black-eyed susan.