Thunbergia, also known as black-eyed Susan vine or clock vine, is a quick-growing vine boasting many open-faced flowers, usually with dark centers (hence the name "black-eyed Susan").
Where not struck down by frost it is a perennial, but most climates of the United States grow it as a beautiful annual. The name Thunbergia honors a Swedish botanist named Karl Pehr Thunberg.
Black-eyed Susan vine can grow 6 to 8 feet tall in a season and has rough, hairy leaves. The blooms have 5 distinct petals and are symmetrical. Flower color can be white, yellow, orange, or cream. Most of them have dark centers.
Generally, it grows best in full sun. It needs average, well-drained soil. Plant seedlings 3 inches away from supports. Space plants 5 to 8 inches apart. Pinch the tips to encourage branching. Since thunbergias climb by twining, netting or strings make good trellising materials. They will need a trellis to climb large posts or solid fencing.
Sow seeds outdoors after the last frost or start seedlings indoors 6 to 8 weeks before outdoor planting. Plant the seeds at a depth of 1/4". Fluctuating temps between about 70 degrees/night-85 degrees/day help germination, which occurs in 10-20 days. Use of potting soil during transplant (ready to transplant at 2 sets of true leaves) will help this nutrient hungry plant.
Thunbergias can be used to cover posts, porches, arbors, pergolas, or fences. They also make good container plants. Plants in containers will also bloom over winter in sunny windows.