The black-eyed Susan vine (Thunbergia alata) is a tropical perennial that is often grown as an annual flowering vine. It is a frequent sight in hanging baskets at the garden center. This flowering vine is as easy to care for as it is charming. The flowers look daisy-like at a distance, with five overlapping, solid-colored petals surrounding a brownish-purple center tube. The medium green leaves are a little coarse and grow opposite one another—they can be either heart-shaped or have a lance-like arrowhead shape.
This fast-growing vine is best planted as a potted nursery plant in the spring once the soil has warmed. It can extend to 8 feet in one growing season. If grown as a perennial in a warm climate, it will be relatively short-lived, but it colonizes readily by self-seeding. This talent for self-seeding can be a problem, as this plant can be invasive in warmer climates.
|Common Names||Black-eyed Susan vine, clockvine|
|Botanical Name||Thunbergia alata|
|Plant Type||Perennial, annual, vine|
|Mature Size||3–8 ft. tall, 3–6 ft. wide|
|Sun Exposure||Full, partial|
|Soil Type||Loamy, rich, well-draining|
|Bloom Time||Spring, summer, fall|
|Flower Color||Red, rose, orange, yellow, white|
|Hardiness Zones||10-11 (USDA)|
Black-Eyed Susan Vine Care
This plant generally does well if planted in any rich, well-draining soil in a sunny location, but it will need some kind of supporting trellis or structure to cling to. These vines will tangle themselves around the nearest support or spill over planter edges. They are perfect for hanging containers and flow just as easily over walls and raised garden beds. A lattice or metal fence makes a good choice for weaving your vines into a living wall, but these plants will clamber over just about anything—from a mailbox pole to an old tree stump.
Black-eyed Susan vines bloom repeatedly from May through fall, and no deadheading (removing spent flowers) is required to keep them in bloom.
This vine is native to eastern Africa and grows as a perennial in tropical climates. It is considered an invasive species in much of the world, including in the state of Hawaii. If you live in plant hardiness zones 10 or 11 and wish to grow black-eyed Susan vine outdoors, check with local authorities to make sure it is not invasive in your area.
You will get the most flowers and the healthiest plants if you grow your black-eyed Susan vines in full sun (at least six hours of direct sunlight on most days). The exception is in hot, dry climates, where growing the plants in partial afternoon shade is recommended.
Black-eyed Susan vines like a well-draining soil that is rich in organic matter with a fairly neutral soil pH (6.6 to 7.7). It can be helpful to work several inches of compost into the soil before planting.
Although these vines don't like sitting in soggy soil, they also don't like being hot and dry. Aim to keep the soil moderately moist. Mulching around the base of the plants will help to keep the roots cool and moist. Generally speaking these plants will do well with the standard rule: 1 inch of water, rainfall and/or watering per week. Extremely hot dry weather may mean more watering is needed, but on weeks where there is plentiful rainfall, you won't need to water at all. It's best to water again whenever the top inch or so of soil feels dry to the touch.
Temperature and Humidity
Black-eyed Susan vines are reliably perennial only in USDA hardiness zones 10 to 11. Thus, in cooler areas, they are usually grown as annuals (removed from the garden after one growing season). But because black-eyed Susan vines are technically perennials, you can put them in a container and bring them indoors for the winter if you're outside of the recognized hardiness zones. Black-eyed Susan vines grown indoors may flower in the winter if they get ample sun and the temperature doesn't fall below 60 degrees Fahrenheit.
Humidity is usually not an issue for these plants, but they can struggle in very dry conditions, so make sure the soil remains moist.
Black-eyed Susan vines grow quickly and bloom repeatedly throughout the summer. That means they exert a lot of energy. So they will need a light feeding every four to six weeks with a complete fertilizer to keep them growing well. Plants grown in containers, whether outdoors or as houseplants, should be fed every two to three weeks while the plants are in bloom.
Types of Black-Eyed Susan Vine
If you are purchasing nursery plants, you might only find the vines labeled as orange or yellow. However, there are more varieties available if you buy from seed:
- 'Angel Wings' has white flowers with a hint of fragrance.
- 'African Sunset' has burgundy centers surrounded by red, ivory, and darker shades of apricot and salmon.
- 'Spanish Eyes' shows unusual pastel shades of peach and apricot.
- 'Superstar Orange' has traditional orange petals with a dark center.
- 'Susie Mix' produces flowers in yellow, orange, and white.
- 'Bakeri' has pure white flowers.
- 'Aurantiaca' has excellent yellow-orange flowers.
Propagating Black-Eyed Susan Vine
There are many ways to propagate black-eyed Susan vine, but the most common is by taking stem cuttings to root. Done in fall, this is a good way to perpetuate plants over the winter in colder regions. Here's how to do it:
- In fall while the plant is still actively growing, use clean sharp pruners to snip 4- to 6-inch segments of healthy stem, making the cut just below a stem node.
- Plant the cutting in a small container filled with ordinary potting mix. No covering is required.
- Set the pot in a bright, warm location, such as a sunny window, to grow over the winter.
- In the spring after outdoor temperatures are reliably above 60 degrees Fahrenheit, the root cutting, now showing active growth, can be transplanted into the garden or into outdoor containers.
How to Grow Black-Eyed Susan Vine From Seed
Black-eyed Susan vine is easy to grow from seed. Seeds can be relatively expensive, but that's because this plant's seed is difficult to collect. You can start seed indoors about six to eight weeks before your projected last frost date or direct-seed in the garden after the danger of frost has passed. Soak the large, hard seeds in water for a day or two before planting.
Black-eyed Susan vines don't like having their roots disturbed, so it helps if you start the seed in peat or paper pots that will biodegrade when planted with the seedling. Plant the seeds about 1/4 inch deep, and expect them to germinate within two to three weeks.
Potting and Repotting Black-Eyed Susan Vine
This plant makes an excellent plant for hanging baskets, window boxes, or large mixed containers where it serves as a "spiller" plant. Ordinary commercial potting mix in any well-draining container will suffice. In hanging baskets, it's typical to plant two or three plants in a 10- to 12-inch plastic pot that includes a catch-tray, suspended with wires that will allow the vines to climb.
Most gardeners grow black-eyed Susan vine as an annual, pulling it from containers at the end of the growing season, but it's also possible to move potted plants indoors to continue growing through the winter as a houseplant. But indoor specimens will need plenty of sun, which can be hard to come by during the shortened winter days. Supplemental light may be required in order to keep the plants blooming.
When grown as an annual, these plants are simply pulled from the ground and discarded in the late fall, which helps avoid self-seeding. In warm-winter regions where black-eyed Susan vine can be grown as a perennial, it's best to keep watering and feeding actively through the winter.
Common Pests & Plant Diseases
Black-eyed Susan vine isn't prone to many problems, particularly if the plant has plenty of sun, water, and air circulation. However, whiteflies and spider mites can be potential problems, especially during hot weather or if the plant is brought indoors where there is dry heat. Look out for small insects on the plant, as well as leaf and stem damage. Treat any outbreaks quickly with insecticidal soap.
How to Get Black-Eyed Susan Vine to Bloom
This plant normally blooms readily and repeatedly from late spring into fall, provided its basic needs are met. Plenty of sunlight, water, and regular fertilizing are essential for keeping these plants blooming all season long.
Common Problems With Black-Eyed Susan Vine
There are very few common complaints with black-eyed Susan vine, though gardeners in warm-weather regions sometimes complain about the plant's habit of self-seeding to the point of invasiveness. Even in cold-weather regions, you may dislike the way volunteers readily spring up around areas where plants were growing the previous year. But these volunteers are easily plucked out, and in cold winter zones, they do not persist to colonize.
How is this plant best used in the landscape?
With their quick growth habit and sprawling nature, black-eyed Susan vines can overtake nearby plants and consequently are often grown solo. However, a nice option is to mix a black-eyed Susan vine with another vine that will intertwine with it. Morning glories are often used for this purpose, particularly the purple varieties that provide a nice color combination. Purple hyacinth bean is another good choice.
This is a very popular plant for hanging baskets and window boxes in regions where it is grown as an annual. In zones where black-eyed Susan vine is perennial, the plant can be used to cover porches or fences.
How long does black-eyed Susan vine live?
Even in warm-winter zones, black-eyes Susan vine is a relatively short-lived perennial, though this can be deceptive, since the plant self-seeds so readily that perpetuating colonies are common.
Are there other Thunbergia species to consider?
There are several other species that are sometimes used in landscaping:
- T. erecta (bush thunbergia) is a West African native plant with rich purple flowers.
- T. fragrans (sweet clockvine) has white, fragrant flowers. It is native to India.
- T. grandiflora (Bengal clockvine) is a white-flowering perennial native to india, often used in Florida, southern California, and Hawaii gardens.
- T. laurifolia (laurel-leaved thungergia) is a native vine from India, often grown as a beautiful perennial vine in Hawaii, with purple flowers.
Black-Eyed Susan Vine, Thunberiga alata. University of Wisconsin-Madison Division of Extension.