Named for its visual resemblance to the popular hardy (and toxic) garden flower black-eyed Susan (Rudbeckia spp.), the safer black-eyed Susan vine (Thunbergia alata) is a perfect plant for containers and hanging baskets. It is particularly beloved for its distinctive flowers in vivid colors such as orange and yellow. The flowers have dark centers, like other black-eyed Susan plants. The leaves are arrow- or heart-shaped and grow up to 3 inches long. This climbing vine winds its way up support structures rather than clinging with tendrils. It grows and flowers quickly when planted in warm spring soil. The vine blooms for many weeks in the summer and into fall. This vine is also known for its invasiveness in tropical areas.
|Common Name||Black-Eyed Susan vine, clockvine|
|Botanical Name||Thunbergia alata|
|Plant Type||Flowering vine, annual or perennial|
|Mature Size||3 to 8 ft. tall, 3 to 6 ft. wide|
|Sun Exposure||Full sun to part shade|
|Soil Type||Fertile, well-drained|
|Soil pH||6.5 to 7.5|
|Bloom Time||Summer (as an annual)|
|Flower Color||Orange, white, yellow, red, pink|
|Hardiness Zones||3-9 annual, 10-11 perennial USA|
|Native Area||East Africa|
Black-Eyed Susan Vine Care
Black-eyed Susan vines are usually planted as annuals in containers or hanging baskets with mixed plantings, but they can also be planted in the ground to grow upward to cover trellises, arbors, fences, and other structures. The plant works well to cascade down over retaining walls, and it can also serve as a ground cover.
If propagating or growing from seed, it's best to provide vertical structure in the ground or pots for the seedlings, before the plants even need vertical structures, so you don't have to disrupt the young plants later. You can simply plant them near a fence (with a post or planks they can climb), stand up a cage structure, or erect a tripod, or a tall pole.
Black-eyed Susan vine is a diminutive vine that grows to a maximum of about 8 feet in temperate zones or when grown in containers, although it can grow to 20 feet in frost-free zones, where the plant is evergreen.
Black-eyed Susan vines can be particularly aggressive where they grow year-round. The vine is considered invasive in many tropical areas, including Hawaii and Mexico.
Grow these plants in full sun to part shade. Some afternoon shade is beneficial, especially in warmer climates, as the hottest sun's rays may be damaging.
Plant black-eyed Susan vines in rich, fertile, and well-drained soil. The soil should have medium moisture-retention properties. It prefers a soil pH that is close to neutral.
When the top inch of soil is dry, water regularly and deeply until water drips from the drainage hole. Pour out excess water from the pot's saucer. But if the soil is damp to the touch, do not water for another day or two. Then, keep the soil moist but not too wet. If the leaves begin to wilt, the soil is probably too dry and needs a bit more water. In containers, do not let the soil dry out completely.
Temperature and Humidity
The black-eyed Susan vine thrives in warm, humid climates, which explains why it is invasive in tropical areas. However, it will grow anywhere in its zone range, provided it gets enough water. It tends to flower best after the hottest days of the summer are over.
Feed the plants (indoors or outdoors) every two to three weeks during their bloom season. Follow the package's directions. But in many cases, it's best to use a half-strength solution of fertilizer designed to boost blooming.
Types of Black-Eyed Susan Vines
Cultivars of Thunbergia alata have very similar foliage and overall habits and are mostly distinguished by flower color.
- 'Angel Wings': White flowers
- 'African Sunset': Dark red-purple flowers
- 'Arizona Dark Red': Deep orange-red flowers
- 'Blushing Susie': Apricot and rose flowers
- 'Canary Eyes': Yellow flowers
- 'Lemon A-Peel': Bright yellow flowers with a very dark center
- 'Orange Wonder': Bright orange flowers with no dark center
- 'Raspberry Smoothie': Pale lilac-pink flowers and grey-green foliage
- 'Superstar Orange': Extra-large orange flowers
- 'Susie' mix: Orange, yellow, and white flowers with or without contrasting centers
Propagating Black-Eyed Susan Vines
Propagating this vine from stem cuttings is easier than growing from seeds. Cuttings are usually best done over the winter. Here's how:
- With a sharp, sterilized garden cutting tool, take a cutting several inches from a terminal end of a healthy plant which you will put into a glass of water.
- Remove the bottom leaves of the cutting and dip the end in rooting hormone.
- Place the cutting in a glass of water to root.
- Change the water in the glass every two or so days.
- When the roots thicken, it's time to plant it in a well-draining pot filled with potting soil.
- Grow the plant until spring and then transplant outdoors after the threat of frost has passed.
How to Grow Black-Eyed Susan Vines From Seed
This vine is easily started from seeds sown directly in the garden after the last expected frost date (when the soil is at least 60 degrees Fahrenheit). In colder climates, nursery transplants are normally used. Or, you can start them indoors six to eight weeks before the last frost. Germination occurs about 10 to 14 days after sowing in warmer temperatures of 70 to 75 degrees Fahrenheit, and up to 20 days in cooler temperatures.
Potting and Repotting Black-Eyed Susan Vines
Black-eyed Susan vines grown in large pots with vertical structures can make beautiful decorations outdoors as well as inside your home. You can set a pair flanking a front door or define the edges of a patio or outdoor sitting area. Indoors, a pot of climbing vine can brighten the corner of a sunroom or even a large, bright bathroom.
Use a sturdy pot of any material, but make sure it's strong to hold the heavy roots. Fill the container with top-quality potting mix. Water when the top of the soil is dry to the touch. Feed container plants (indoors or outdoors) every two to three weeks during the blooming period.
Move potted vines indoors so the vines can flower in the winter, provided they get plenty of sun and the temperature doesn't drop below 60 degrees Fahrenheit. Feed indoor wintering container plants every two to three weeks during the cold season's blooming period.
This showy vine is free of most serious insect or disease problems when grown outdoors, but indoors the plants can have problems with scale, spider mites, and whiteflies. Typically, these can be managed with neem oil or horticultural soap.
How to Get Black-Eyed Susan Vines to Bloom
Black-eyed Susan vines are beloved for their summer and fall blooms. There are a few reasons why the vines are not blooming, which can potentially be fixed with some work.
One reason could be because the weather has turned extremely hot or the sun's scorch is causing it to fail to flower. The vine needs to grow in a sunny, cool spot and can't stay in direct heat for more than six hours at a time. Try keeping your vine in the shade during the day to cool off, then it may start blooming.
Other reasons the vine is not blooming could be that the soil is too dry (add mulch to keep it moist). Or, the soil may be too cold because it dropped below 60 degrees Fahrenheit, which you can't control, unfortunately. The vine could also be over-fertilized. Or, your vine is young and it may not bloom during its first year of life so you may need to give it some time.
If your plant is refusing to bloom, it may feel crowded. Use a trellis that can support a stretched-out vine. It may just need a little breathing space to bloom.
Do black-eyed Susan vines need deadheading?
What should you plant near the vine?
Can indoor black-eyed Susan vines bloom indoors in the winter?
Indoor vines can flower in the winter, provided that the vines get plenty of sun and the room temperature doesn't drop below 60 degrees Fahrenheit.