Ornamental · Acanthaceae
Black-eyed Susan Vine
Thunbergia alata
Offer it full sun, steady water, and something to climb, and this twining annual will flower from summer all the way 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 quick, twining climber that gardeners treasure for its long, steady run of cheerful flowers. Though it began life as a tender perennial in East Africa, most gardens treat it as a warm season annual, letting it scramble up a trellis, fence, or hanging basket over a single summer. Its sunny blooms in orange, yellow, and white, most carrying a dark eye, are exactly what gave the plant its name.
Few plants pay you back as generously: it climbs quickly and keeps flowering for ages. Hand it a support to twine around and it will clothe an arbor or tumble from a container, stretching to 3 to 8 feet (91 to 244 cm) across one season. Its flowering carries on from early summer straight through to frost, and it usually puts on its finest show in late summer and fall once the harshest heat has eased.
Take comfort knowing this is an easy plant that wants little more than sun, water, and a place to climb. Protect the soil from drying out during a heat wave and pinch back the young stems for a fuller vine, and it will thank you with months of color even if you are still finding your feet.
Care
The short version: give it full sun to part shade, with a little afternoon shade where summers run hot. Keep the soil evenly moist so it never quite dries out, plant it in rich, well-drained ground with a support to climb, and feed it across the growing season.
Light
Black-eyed Susan vine blooms most happily in full sun, yet it handles part shade with grace. In places where summers grow harsh, a little afternoon shade softens the heat, while too little light leaves you with a leggy plant carrying lots of leaves and only a handful of flowers.
Water
Aim to keep the soil evenly moist, watering often enough that it never dries out, which works out to roughly every 2 to 4 days in warm weather. A vine left thirsty through a hot, dry spell will let go of its buds and flowers, so do your best not to let it run short over summer.
Soil
Set it into rich, fertile, well-drained ground that stays steadily moist, with a good helping of organic matter mixed in. You want soil that holds moisture without turning soggy, and that balance suits garden beds and containers alike.
Temperature
It settles in contentedly between 50°F and 86°F (10°C to 30°C) and cannot withstand any frost. Flowering eases off during the height of summer heat, then surges back as the weather cools toward late summer and fall.
Humidity
Everyday outdoor humidity suits it just fine, so there is no figure to chase. Good airflow matters far more here, because crowded, stagnant growth tends to draw spider mites and whiteflies, especially on plants kept inside.
Feeding
Offer a meal once a month all through the spring and summer growing season using a balanced, general-purpose fertilizer. Regular feeding keeps a quick grower like this one in healthy leaf and bloom, with no single nutrient left wanting.
Pruning
Pinch the young stems early on to encourage side branching and a fuller, bushier vine. As the season rolls along, snip back anything leggy or overgrown to keep things neat and to draw out even more flowers.
Repotting
For container plants, refresh or pot up each spring so the roots gain room and the mix is renewed. Keep an eye out for roots winding around the pot or poking out the drainage holes, water that rushes straight through, and growth that has stalled, each one telling you it has outgrown its home.
Size & spacing
Trained on a support, the vine reaches 3 to 8 feet (91 to 244 cm) tall and fans out 3 to 6 feet (91 to 183 cm) wide over one season. Allow it space and a trellis or fence to twine around so it always has somewhere to head.
When to plant
Warmth is everything to this vine, and frost is simply not on the menu. Sow your seeds indoors in early spring, move the plants outside only after the cold has truly gone and the soil has warmed up, and then settle in to enjoy the flowers from early summer until frost closes 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
Nearly every hiccup with this vine comes down to heat, light, or pests, and the first clues turn up in either the flowers or the leaves. Catch those early signals and you can act before the blooms start to fade. Find the picture that matches yours below, then step in while it still does some good.
Buds and flowers slipping away in hot, dry weather
What you are seeing is heat and drought stress, and it is not a disease, so take heart. When the soil bakes dry through a hot run, the vine simply pauses its flowering to look after itself, and it will start blooming again as the heat lets up into late summer and fall. You can help by watering on a steady schedule to hold even moisture, tucking mulch over the roots to keep them cool, and offering afternoon shade in places where summers turn fierce.
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
Speckled, sticky leaves with webbing or tiny insects
When foliage turns speckled, sticky, or webbed, the visitors are usually spider mites, whiteflies, aphids, or scale, and they tend to settle on plants that are stressed or kept indoors. Flip a leaf over to spot who is responsible, knock them loose with a firm jet of water, and then treat the undersides with insecticidal soap or horticultural oil. A repeat round of treatment plus better airflow, especially for indoor plants, usually sets things right.
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
Lots of leaves but hardly any flowers
When a vine stretches out long and leafy yet holds back its blooms, the cause is almost always too much shade. Since this plant flowers happiest in full sun, gently shift a container into a brighter corner and try for at least several hours of direct light each day. Once it gets the sunshine it craves, the flowers come along behind.
Fix:
- Move container plants to a sunnier spot
- Site in full sun to part shade with at least several hours of direct sun
Toxicity
Here is some reassuring news for homes full of animals: the black-eyed Susan vine carries no listing as toxic to pets or people. You can grow it happily where cats, dogs, and inquisitive children all share the garden. As with any plant, a generous mouthful of leaves might bring on a little passing stomach upset, so it is still kind to gently steer pets away from chewing on it.
Safe for
People · Cats · Dogs · Horses · Rabbits · Livestock · Birds
Cats Safe
A nosy cat may nibble the leaves with no harm done, because this vine does not appear on the ASPCA toxic list. Should it gulp down a large mouthful of greenery, you might see a touch of drooling or a hairball, and nothing beyond that.
Dogs Safe
Dogs do just fine sharing space with this plant. At worst, a nibble leads to a brief spell of mild tummy upset, much like it would with most ornamental leaves.
Horses Safe
There is no toxicity on record for horses. A horse munching a stray vine here and there will come to no genuine harm.
Rabbits Safe
Rabbits are welcome to browse the leaves safely. With any unfamiliar green, ease it in slowly so an abrupt diet shift does not upset their digestion.
Livestock Safe
There is no documented danger to cattle, goats, or sheep from this vine, so a mouthful out in the pasture need not concern you.
Birds Safe
Birds face no known threat from the plant. Backyard hens are free to peck at its leaves and seeds without any trouble.
People Safe
No cases of poisoning in people have ever been recorded, and this vine is raised for its flowers and not for the table. Keep a gentle watch over small children, who really should not be tasting garden plants in any case.
As with any plant, ingestion of plant material may cause mild, transient stomach upset in pets.
Varieties
Most black-eyed Susan vines reach gardeners as seed series chosen for a range of warm flower colors. These are the names you are most likely to meet.
Susie series
A much-loved seed series available in orange, yellow, and white, offered both with and without the signature dark eye.
Arizona series
A strong-growing series in warm orange, apricot, and gold tones, with every bloom framed by a dark center.
Spanish Eyes
Wraps soft terracotta and apricot tones around a dark eye to give a warmer, gentler, muted look.
Blushing Susie
Brings together tender apricot, rose, and ivory tones, frequently with eyes that soften away rather than stand out.
Alba
A crisp white-flowered form that still holds onto the typical dark purple-black eye.
How to propagate
Multiplying this vine is wonderfully forgiving, whether you open a fresh seed packet each spring or take cuttings to usher a favorite plant safely 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
Growing from seed is the everyday way to raise this annual vine, and it could hardly be simpler. Get it going indoors 6 to 8 weeks before your last frost, or drop the seeds right into warm ground once the frost is behind you, and they will sprout in about one to three weeks. After that, give it a few weeks to a couple of months and the vine will be climbing and opening its first flowers.
Stem cuttingsModerate
Take cuttings in late summer for overwintering indoors. · A few weeks to root
Taking cuttings is your way to bring a treasured plant safely through the winter. Snip them in late summer, let them root over a few weeks, and settle the young plants in a warm, sunny window until spring arrives. It does ask for a little more attention than seed, yet it lets you hold onto a variety you would love to grow again.
Myths
Black-eyed Susan vine is the same plant as the Black-eyed Susan wildflower.
A shared name and a dark center are all the two have in common. Black-eyed Susan vine (Thunbergia alata) is a tender twining annual climber in the family Acanthaceae, native to East Africa. By contrast, the wildflower Black-eyed Susan (Rudbeckia hirta or fulgida) is an upright, daisy-like perennial or biennial belonging to the aster family. They are completely different plants that simply resemble one another at the bloom's eye.