Description
Black-eyed Susan vine is commonly grown in the Midwest as a season annual to provide color in a vertical setting. This plant, Thunbergia alata, is actually a tender evergreen perennial in the acanthus family (Acanthaceae) native from tropical East Africa to eastern South Africa that is hardy only in zone 9 and 10 (and is completely unrelated to Rudbeckia hirta, an herbaceous annual or short-lived perennial in the daisy family (Compositae) native to north America also commonly called black-eyed Susan). But because it grows and flowers relatively quickly it is often used as an annual ornamental garden plant in cooler areas. It should be used with caution in frost-free areas as it has become invasive in many warm locations throughout the world.
The plant is a rambler, climbing by twining (growing in a spiral up a support) rather than by clinging or producing tendrils as some other vines do. The opposite, oval to triangular or heart-shaped leaves grow up to 3 inches long on winged petioles. They are soft and hairy, dull dark green on the upper surface and pale green with prominent veins below, with slightly toothed margins.This vine grows by twisting around supports and has heart-shaped, softly hairy leaves.
Showy flowers in shades of orange and yellow are produced singly in the leaf axils. Each 1½ inch wide flower emerges from a small yellow-green calyx enclosed in 2 large, ridged, hairy, green bracts. The trumpet-shaped corolla opens flat with five overlapping petals surrounding the brownish-maroon center.
