Caren White is a Master Gardener and instructor at Home Gardeners School. She has been associated with Rutgers Gardens for over a decade.
I love black-eyed Susans. I grow both kinds, the annual and the perennial ones. I can’t get enough of them so you can imagine my delight in discovering the black-eyed Susan vine. Except that it wasn’t really a black-eyed Susan.
What are Black-Eyed Susan Vines?
Black-eyed Susan vines (Thunbergia alata) are flowering vines that are native to eastern Africa. They have become naturalized in Australia, Brazil, Hawaii, Texas, Florida and Puerto Rico. They are hardy in zones 9 – 11. Most gardeners grow them as annuals.
They are not related to Black-eyed Susans. They get their name from their resemblance to those popular flowers. From a distance, the vines look just like Black-eyed Susans, but when you get up close you can clearly see the difference. Black-eyed Susan vine flowers are not discs with petals surrounding them. Instead, they are tubular. They consist of five petals that are usually yellow while the throat of the flower is a dark brown. Newer cultivars sport flowers in orange, white, red or salmon. Not all of them include the characteristic dark centers.
The vines can grow to 6 to 8 feet long. They climb by twining around supports. The vines can be grown in hanging baskets or climb up tepees, tuteleurs, trellis, arbors or along fences. They can even be grown in containers as long as you provide something for them to climb.
How to Grow Black-Eyed Susan Vines
Choose a sunny spot in your yard. Black-eyed Susan vines like full sun. They can tolerate a little shade, but won’t bloom as well for you. If you don’t provide support for them, they will sprawl across the ground. Keep them well-watered. They like their soil to be moist so don’t let them dry out between waterings. A thick layer of mulch will help keep the soil moist.
These vines grow and bloom quickly. To keep them growing, fertilize them monthly with a balanced fertilizer such as 10-10-10.
If you are growing your vine in a container with a small trellis, it will probably rapidly outgrow the trellis. You can safely prune your vine to keep it to a manageable size.
Black-eyed Susan vines bloom continuously during the summer. There is no need to deadhead them.
Can Black-Eyed Susan Vines be Grown Indoors?
Black-eyed Susan vines are not suitable as houseplants because they require full sun and our homes do not have enough light for them. What you can do instead is to grow your vine in a container outdoors during the summer and then bring it indoors in the fall when night time temperatures fall below 50⁰F. Place it in your sunniest window. During the winter when the vine is not actively growing, it will not require as much light so you should be able to keep it alive until spring. In the spring, move your plant back outdoors when night time temperatures are consistently above 50⁰F.
If your window is sunny enough and night time temperatures in your home are above 60⁰F, you may be rewarded with a few flowers during the winter.
When you bring your vine indoors, it may be quite large and ungainly. You can prune it to keep it a manageable size while it is in your home. It will not grow much during the winter, but when you move it back outdoors and the temperature warms up, your vine will start to grow vigorously again.
How to Grow Black-Eyed Susan Vines From Seed
Most gardeners grow their Black-eyed Susan vines from seed. The seed coats are very hard so you will need to soak them overnight before planting them. I use what I call the cup & saucer method. I soak my seeds in teacups which I cover with their saucers to keep my curious cats (or curious children if you have them) out. Because I am usually soaking different kinds of seeds, I place the seed packet under the teacup so I know what seed is in each cup.
You can direct sow your seeds in your garden in the spring when they soil has warmed to 60⁰F. Install your support system where you intend to grow your vines. The reason you would want to direct sow the seeds in your garden is that the plants do not transplant well because they don’t like having their roots disturbed. Plant the seeds ¼ inch deep around the support. Germination should occur in 2 to 3 weeks. I always keep an eye on any vines I am growing to make sure that they are able to climb the support. Sometimes I have to give them a little help by guiding them to the support. Occasionally I even loosely tie the vines to the support using string which I remove later.
You can also start your seeds indoors. It’s best to use biodegradable containers such as peat pots because black-eyed Susan vines do not like their roots disturbed. Using a peat pot allows you to transplant your seedlings, pot and all, into your garden without disturbing the roots. The pot will gradually break down during the growing season and add nutrients to the soil.
After pre-soaking your seeds, fill your peat pots with soil and plant your seeds ¼ inch deep 6 to 8 weeks before your last frost. Keep the soil moist. Germination should occur in 2 to 3 weeks. You can plant your seedlings in your garden after all danger of frost has passed and night time temperatures are consistently above 50⁰F. Be sure to install your supports before you plant your seedlings. If you plant your seedlings first and then try to install your supports, you will risk damaging your plants.
© 2019 Caren White