How to Grow Black-Eyed Susan Vine

Botanical name:

Thunbergia alata

Common names:

Black-eyed Susan vine, clock vine, bright eyes
(Note: Although the flowers bear a resemblance to black-eyed Susan (Rudbeckia), the plants are not related.)

Plant type:

Tender perennial, usually grown as an annual

Zones:

10-11

Native area:

East Africa

Exposure:

Full sun to part shade

Method of attachment:

Twining stems

Height:

3 to 8 feet

Bloom time:

Blooms continuously from early summer until frost, usually putting on the best show from late summer to early fall.

Flower colors and characteristics:

Five-petaled flowers, 1 to 2 inches across, come in shades of yellow, orange, red, coral, white, or bicolor, with dark purple or black throats.

Foliage:

Heart-shaped or triangular leaves grow up to 3 inches in length. Color ranges from deep green to gray-green.

Photo by Elsa Cadic / Shutterstock

Where to plant:

These plants grow best in a sunny site sheltered from strong winds and drafts. If you live in a hot, dry climate, plant them in a spot that receives some afternoon shade.

When to plant:

For the earliest flowers, start seeds indoors 6 to 8 weeks before your last frost date in spring. You can also start plants from seed sown directly in the garden after the last frost. If growing from transplants, plant them in the spring once the soil has warmed up and nights stay consistently above 50° F.

How to plant:

Set out nursery-grown transplants at the same depth they were growing in the container, spacing them at least a foot apart.

If growing from seeds, plant them about 1/2 inch deep, covering them with a fine layer of soil. Don’t worry if the seedlings take awhile to emerge. Black-eyed Susan seeds often require as long as 21 days to germinate.

If you want your plants to climb a vertical support such as a trellis or plastic netting, install it before planting seeds or transplants so you don’t disturb the young plants.

Soil:

Prefers moist, well-drained, fertile soil that is rich in organic matter. If growing in containers, use a high-quality all-purpose potting mix that drains well.

Tip:

If you want your black-eyed Susan vines to climb a support, they will need a little coaxing to get started. You can secure young shoots to the base of the support with gardener’s wire or coated twist ties until the plant has secured itself. As the vines grow, any stray or wayward shoots can be carefully twisted around the support. Black-eyed Susan vines naturally twine counterclockwise, so keep that in mind when training them.

Water:

Like most tropical plants, Thunbergia alata does not tolerate drought. Water regularly throughout the growing season to keep the soil evenly moist but not soggy. Plants grown in containers may need more frequent watering. Wilting foliage is often the first sign that your plants are thirsty.

Amendments and fertilizer:

In the garden, the application of a controlled-release fertilizer at planting time is usually sufficient to keep plants thriving. Also work some compost or other organic matter into the soil to improve drainage and soil fertility.

Container-grown plants will also benefit from the use of a controlled-release fertilizer while plants are in bloom; follow directions on the label. Avoid over-fertilizing, which can inhibit flowering.

Pruning and deadheading:

Light pruning can be done as needed throughout the growing season to help shape plants and manage their size. Deadheading is not necessary to keep these vines in bloom.

Propagation:

By seeds or stem cuttings taken in summer.

Overwintering indoors:

In climates where black-eyed Susan vines aren’t hardy, potted plants can be moved indoors in late fall (or as soon as nighttime temperatures fall below 50 degrees F) and grown in a sunny window as a houseplant. Given enough sun or supplemental artificial lighting, plants may continue to bloom, although not as profusely.

Pests and diseases:

Black-eyed Susan vines are generally not affected by diseases or pests, but plants can occasionally be susceptible to whiteflies and spider mites, especially when grown indoors.

Is black-eyed Susan vine an annual or perennial?

Although usually grown as an annual, it is actually a tender evergreen perennial in frost-free climates (zones 10-11).

Is black-eyed Susan vine fragrant?

The flowers of some varieties have a hint of fragrance, but if you’re looking for a vine that is strongly fragrant, mandevilla, sweet pea, or honeysuckle are good alternatives. Despite the lack of scent, bees and butterflies will still flock to the colorful blooms.

Do black-eyed Susan vines grow fast?

Although they can be slow to germinate, the vines will shoot up quickly once they become established, growing 6 inches or more per week under ideal conditions.

Is black-eyed Susan vine deer resistant?

Because the foliage of Thunbergia is slightly coarse and hairy, it is not very palatable to foraging deer. However, be on the look out for signs of browsing.

Is black-eyed Susan vine poisonous?

No. It’s generally considered to be safe according to the University of California list of safe garden plants. However, consuming any part of the plant is not recommended.

Is black-eyed Susan vine invasive?

Because it self-seeds readily, it can become invasive in tropical, frost-free climates. This is rarely a problem in areas where it’s grown as an annual.