Thunbergia alata, commonly known as Black-eyed Susan vine, is a fast-growing and cheerful climber beloved for its bright flowers and vigorous habit. It is not to be confused with the similarly named Rudbeckia (also called Black-eyed Susan), which is a daisy-like ground-dwelling perennial.

Thunbergia alata is native to eastern Africa, including countries like Kenya, Tanzania, and Ethiopia. It thrives in tropical and subtropical regions and has since naturalised in parts of Asia, the Pacific Islands, and Australia, particularly in warmer climates.

The most well-known colour is a vibrant orange with a dark purplish-black centre—hence the name “Black-eyed Susan vine.” However, it also comes in a range of other shades:

• Creamy white (e.g., ‘Alba’)

• Soft yellow

• Apricot

• Peach

• Deep red-orange

• Mixes and pastels, this is a mix of all of the above.

The flowers are typically five-petalled and bloom continuously throughout the warmer months.

How it Grows

Thunbergia alata is a fast-growing annual or perennial climber, depending on your climate. In most parts of Australia, it is treated as an annual unless protected from frost. It can grow 2–3 metres or more in a single season when given support.

It prefers:

• Full sun to part shade

• Well-drained, rich soil

• Regular watering (but not soggy)

• Mulching to keep roots cool and retain moisture

• A trellis or support structure, as it climbs by twining

It is ideal for fences, arches, hanging baskets, or as a quick screen.

Growing from Seed

Thunbergia alata is easy to grow from seed and is typically sown in spring after the danger of frost has passed.

What the seeds need:

• Warmth to germinate – ideal soil temperature is around 20–25°C

• Moisture, but not waterlogging

• Light soil or potting mix for best sprouting results

How to sow:

1. Scarify the seeds lightly (optional) by nicking them or soaking them in warm water overnight to speed up germination.

2. Sow seeds 1 cm deep in seed-raising trays or small pots.

3. Keep the soil moist but not wet.

4. Germination typically takes 7–21 days depending on temperature.

5. Transplant to a sunny garden spot or large pot once seedlings have 2–3 true leaves and all risk of frost is past.

6. Space plants 30–50 cm apart if planting in the ground.

7. Provide something for them to climb on immediately, as they’ll grow quickly once established.

Final Notes

Thunbergia alata is a stunning and satisfying plant to grow—excellent for beginners, great for quick coverage, and rewarding with its vivid colours. In warm parts of Australia, it may self-seed and return year after year, but in colder zones, it’s best grown anew each spring.