Ornamental · Acanthaceae
Black-eyed Susan Vine
Thunbergia alata
Give it full sun, steady water, and something to climb, and this twining annual flowers from summer to frost.
Full sun
Every 2–4 days
50–86°F · 10–30°C
70–100 days
Overview
The black-eyed Susan vine is a fast, twining climber grown for its steady run of cheerful flowers. It's a tender perennial from East Africa, but in most gardens it's grown as a warm season annual, scrambling up a trellis, fence, or hanging basket in a single summer. The bright blooms in orange, yellow, and white, most marked by a dark eye, give the plant its name.
It earns its keep by climbing fast and flowering long. Give it a support to twine around and it will cover an arbor or spill from a container, reaching 3 to 8 feet (91 to 244 cm) in a season. The flowering runs from early summer right up to frost, and it tends to look its best in late summer and fall once the worst heat has passed.
This is an easy plant that asks for little beyond sun, water, and something to climb. Keep the soil from drying out in a heat wave and pinch the young stems for a fuller vine, and it rewards you with months of color.
Care
The short version: full sun to part shade, with afternoon shade where summers run hot. Keep the soil evenly moist so it never dries out, give it rich, well-drained ground and a support to climb, and feed it through the growing season.
Light
Black-eyed Susan vine flowers best in full sun, though it takes part shade in stride. Where summers turn brutal, a bit of afternoon shade eases the heat, but too little light gives you a leggy plant with plenty of foliage and few blooms.
Water
Keep the soil evenly moist and water often enough that it never dries out, roughly every 2 to 4 days in warm weather. A vine that goes dry in a hot, dry spell will drop its buds and flowers, so don't let it run short during summer.
Soil
Plant it in rich, fertile, well-drained ground with steady moisture and plenty of organic matter worked in. The soil should hold water without staying soggy, which suits both garden beds and containers.
Temperature
It grows happily between 50°F and 86°F (10°C to 30°C) and has no tolerance for frost. Bloom slows in the peak of summer heat, then comes on strong again as the weather cools into late summer and fall.
Humidity
Ordinary outdoor humidity is fine, so there's no number to hit. Good airflow matters more here, since stagnant, crowded growth invites spider mites and whiteflies, especially on plants kept indoors.
Feeding
Feed monthly through the spring and summer growing season with a balanced, general-purpose fertilizer. Steady feeding keeps a fast grower like this in leaf and flower without any one nutrient running short.
Pruning
Pinch the young stems early to push side branching and a fuller, bushier vine. Through the season, trim back any leggy or overgrown stems to keep it tidy and coax out more flowers.
Repotting
In containers, refresh or pot up each spring to give the roots room and renew the mix. Watch for roots circling the pot or poking through the drainage holes, water that runs straight through, and stalled growth, all signs it's outgrown its home.
Size & spacing
Grown on a support, the vine climbs 3 to 8 feet (91 to 244 cm) tall and spreads 3 to 6 feet (91 to 183 cm) wide in a season. Give it room and a trellis or fence to twine around so it has somewhere to go.
When to plant
This vine wants warmth and won't tolerate frost. Start the seeds indoors in early spring, set the plants out once the cold has fully passed and the soil has warmed, and enjoy the flowers from early summer until frost ends the season.
Northern hemisphere
Southern hemisphere
Typical months for a temperate climate: start earlier in warm zones, later where spring frosts linger.
- Sow: 6-8 weeks before last spring frost
- Plant: after last spring frost when soil and air have warmed
- Harvest: early summer to frost; best bloom in late summer and fall after peak heat moderates
Hardiness
USDA hardiness zones: 10–11
Temperature: down to -1°C
Troubleshooting
Most trouble with this vine traces back to heat, light, or pests, and it shows up first in the flowers or the leaves. Read those early signs and you can step in before bloom falls off. Match what you see below, then act while it still helps.
Buds and flowers dropping in hot, dry weather
This is heat and drought stress, not a disease, and it shows up when the soil dries out during a hot stretch. The vine stops blooming to protect itself, then picks back up once the weather eases in late summer and fall. Water regularly to hold even moisture, mulch the roots to keep them cool, and give the plant afternoon shade where summers run hot.
Fix:
- Water regularly to keep soil evenly moist during heat
- Provide afternoon shade in hot climates
- Mulch to conserve soil moisture and keep roots cool
Stippled, sticky leaves with webbing or small insects
Spider mites, whiteflies, aphids, or scale move in on stressed and indoor plants, leaving foliage speckled, sticky, or webbed. Turn a leaf over to find the culprit, then knock them back with a strong spray of water and follow up with insecticidal soap or horticultural oil on the undersides. Repeat the treatment and open up the airflow, especially on plants kept inside.
Fix:
- Rinse foliage with a strong spray of water to dislodge mites and aphids
- Apply insecticidal soap or horticultural oil, covering leaf undersides
- Repeat treatments and improve airflow for indoor plants
Plenty of leaves but barely any flowers
Too much shade is the usual reason a vine grows long and leafy yet refuses to bloom. The plant flowers best in full sun, so move a container to a brighter spot and aim for at least several hours of direct light. Give it the sun it wants and the flowers follow.
Fix:
- Move container plants to a sunnier spot
- Site in full sun to part shade with at least several hours of direct sun
Toxicity
Good news for households with animals: the black-eyed Susan vine isn't listed as toxic to pets or people. It's safe to grow where cats, dogs, and curious children share the garden. As with any plant, a big mouthful of foliage might cause a little passing stomach upset, so it's still worth discouraging pets from chewing on it.
Safe for
People · Cats · Dogs · Horses · Rabbits · Livestock · Birds
Cats Safe
A curious cat can chew the leaves without harm, since this vine isn't on the ASPCA toxic list. A big mouthful of any greenery might bring on a little drooling or a hairball, nothing more.
Dogs Safe
Dogs are fine around this plant. The most a nibble tends to cause is a passing bout of mild stomach upset, the same as with most ornamental foliage.
Horses Safe
No toxicity is recorded for horses. Grazing on a stray vine won't do any real harm.
Rabbits Safe
Rabbits can browse the foliage safely. As with any new green, introduce it gradually so a sudden change of diet doesn't loosen their gut.
Livestock Safe
Cattle, goats, and sheep face no documented danger from this vine, and a mouthful in the pasture is nothing to worry about.
Birds Safe
The plant poses no known threat to birds. Backyard hens can peck at the leaves and seeds without trouble.
People Safe
There's no record of poisoning in people, and the vine is grown purely for its flowers rather than for eating. Keep an eye on small children, who shouldn't be sampling garden plants regardless.
As with any plant, ingestion of plant material may cause mild, transient stomach upset in pets.
Varieties
Most black-eyed Susan vines are sold as seed series bred for a range of warm flower colors. These are the ones you'll run into most often.
Susie series
A popular seed series that comes in orange, yellow, and white, with or without the signature dark eye.
Arizona series
A vigorous series in warm orange, apricot, and gold shades, each bloom set off by a dark center.
Spanish Eyes
Blends soft terracotta and apricot tones around a dark eye for a warmer, muted look.
Blushing Susie
Mixes gentle apricot, rose, and ivory shades, often with eyes that fade rather than stand out.
Alba
A clean white-flowered form that keeps the characteristic dark purple-black eye.
How to propagate
This vine is easy to multiply, whether you start fresh from a seed packet each spring or take cuttings to carry a favorite plant through the winter.
SeedEasy
Start indoors 6-8 weeks before last frost, or sow directly outdoors after the last frost. · Germinates in about 1-3 weeks; weeks to a few months to a flowering vine
Seed is the usual way to grow this annual vine, and it's an easy one. Start it indoors 6 to 8 weeks before your last frost or sow it straight into warm ground once the frost has passed, and the seeds sprout in about one to three weeks. From there it takes a few weeks to a couple of months for the vine to climb and come into flower.
Stem cuttingsModerate
Take cuttings in late summer for overwintering indoors. · A few weeks to root
Cuttings are how you carry a favorite plant through winter. Take them in late summer, root them over a few weeks, and keep the young plants in a warm, sunny window until spring. It takes a bit more care than seed, but it saves a variety you want to grow again.
Myths
Black-eyed Susan vine is the same plant as the Black-eyed Susan wildflower.
They share a name and a dark center, but that's where it ends. Black-eyed Susan vine (Thunbergia alata) is a tender twining annual climber in the family Acanthaceae, native to East Africa. The wildflower Black-eyed Susan (Rudbeckia hirta or fulgida) is an upright, daisy-like perennial or biennial in the aster family. They are completely different plants that happen to look alike at the bloom's eye.