Thunbergia plants are vigorous vines that can be grown on a trellis, over an arbor or along a fence. The most common ones are Black-eyed Susan Vine (Thunbergia alata) and Bengal Clock Vine (Thunbergia grandiflora).
The Black-eyed Susan Vine has bright yellow or orange flowers with darker centers. It blooms from mid-summer to fall. Some varieties have flowers in shades of ivory, peach or rose. It grows 6 to 10 feet high.
The flowers of the Orange or Golden Clock Vine (Thunbergia gregorii) are similar, but they do not have dark eyes. The vine grows 20 feet tall and blooms from spring to fall.
The Bengal Clock Vine, also called Blue Sky Vine, has clusters of funnel-shaped, sky-blue flowers in summer and fall. It grows rampantly and has to be pruned regularly.
The Laurel Clock Vine (Thunbergia laurifolia) has lavender-blue flowers. It has stiff, narrow leaves, while the Bengal Clock Vine has leathery, heart-shaped leaves.
Bush Clock Vine (Thunbergia erecta) is also called King's Mantle. It is a shrub that grows 6 feet high and wide. It has small leaves and flowers that are purple with yellow throats, appearing singly or in clusters.
The Scrambling Sky Flower (Thunbergia battiscombei) has brilliant blue-purple flowers from mid-summer to fall. It is smaller and less rampant than the Bengal Clock Vine. It can be grown without support and will form a symmetrical mound 4 feet high and 6 feet across.
Lady Slipper Vine (Thunbergia mysorensis) has long chains of unusual lipped flowers. It is also called Brick and Butter Vine because the flowers are russet red and yellow. It is an exotic vine and attracts hummingbirds.
Sweet Clock Vine (Thunbergia fragrans) has small fragrant flowers. The flowers of white, yellow, lavender or blue can grow singly or in clusters.
Most Thunbergias are root hardy to Zone 8. They will be killed to the ground by freezing temperatures, but return in the spring. They can be grown in full sun to partial shade in well-drained soil. Thunbergias grow vigorously. Some varieties can become invasive if they are not pruned regularly.