Black Eyed Susan Vine

Thunbergia alata is native to eastern Africa, including Kenya, Tanzania, Uganda, Mozambique, and eastern South Africa, where it grows in forest margins, scrub, and disturbed areas in warm, moist conditions.

• Named in honor of Carl Peter Thunberg (1743–1828), a Swedish botanist and student of Linnaeus who traveled extensively in South Africa and Japan and is sometimes called the "father of South African botany"
• The species name alata means "winged," referring to the winged stems or winged petioles
• Introduced to European horticulture in the early 19th century and quickly became a popular annual vine
• The common name "Black Eyed Susan" is shared with the unrelated North American wildflower Rudbeckia hirta — both have yellow flowers with dark centers
• Has naturalized widely in tropical and subtropical regions worldwide, including parts of Hawaii, Central America, and Southeast Asia
• In some tropical regions it has become weedy, though it is not generally considered a serious invasive species
• The genus Thunbergia contains approximately 100 species of tropical vines and shrubs, primarily from Africa and Asia
• One of the top-selling annual vines in the world, widely available as seed and transplants
• Modern cultivar breeding has expanded the color range well beyond the original orange-yellow

Black Eyed Susan Vine is a herbaceous to slightly woody annual vine climbing by twining stems to heights of 1.5–2.5 m, with a vigorous, scrambling habit.

Stems: Slender, green, somewhat angular or winged (hence alata), twining around supports. Stems are moderately hairy.

Leaves: Opposite, ovate to hastate (arrowhead-shaped), 4–10 cm long and 3–7 cm wide, medium green, slightly hairy, with toothed or lobed margins and a pointed tip. The leaf base often has two small lobes that give it a distinctive arrowhead shape.

Flowers: The cheerful signature feature — produced singly from the leaf axils on slender pedicels. Each flower is trumpet-shaped, 3–5 cm across, with 5 broad, rounded petals that are typically bright orange-yellow with a striking dark purple-black to chocolate-brown center (throat). The dark center is the "black eye" that gives the vine its name. Cultivars expand the color range to include pure yellow, white, salmon-pink, rose-pink, and even near-red, often with or without the dark center. Flowers last only one day but are produced in such profusion that the vine is never without blooms.

Fruit: Small, beaked capsules containing 4–6 seeds. In warm climates, the vine self-seeds freely.

Roots: Fibrous root system. Relatively shallow-rooted.

Black Eyed Susan Vine grows naturally in forest margins, scrub, roadsides, and disturbed areas in the warm, moist regions of East Africa, where it scrambles through low vegetation.

• Thrives in full sun to light partial shade — best flowering in full sun
• Prefers warm temperatures (20–30°C) and moderate to high humidity
• Tolerates a wide range of soils provided they are well-drained — adapts to poor soils
• Flowers continuously from early summer until killed by frost — an exceptionally long bloom period
• Individual flowers are short-lived but produced in incredible profusion
• The bright colors and dark "eye" pattern attract butterflies and other pollinators
• In tropical regions, the vine can be somewhat weedy and self-seeds aggressively
• Not shade-tolerant — flowering diminishes dramatically in low light
• Relatively pest-free but can be attacked by spider mites in hot, dry conditions
• The plant is not frost-tolerant and is killed by temperatures below 5°C

Black Eyed Susan Vine is one of the easiest and most rewarding annual vines to grow from seed.

From Seed: Sow seeds indoors 6–8 weeks before the last frost date, or sow directly outdoors after all frost danger has passed. Soak seeds in warm water for 12 hours before sowing to improve germination. Plant 6 mm deep. Germination takes 7–14 days at 21–24°C. Transplant seedlings outdoors after hardening off.

Site Selection: Full sun. Plant at the base of a trellis, fence, netting, obelisk, or allow to trail from hanging baskets and window boxes.

Soil: Any well-drained soil. Adaptable to poor soils. pH 5.5–6.5. Incorporate compost at planting.

Spacing: Space plants 20–30 cm apart. Plant 3–4 seeds per hill, thinning to the strongest.

Watering: Regular watering — keep soil moist but not waterlogged. Drought-tolerant once established but flowers best with consistent moisture.

Fertilization: Feed every 2–3 weeks with a balanced liquid fertilizer during the growing season. Excess nitrogen promotes foliage at the expense of flowers.

Support: Provide thin supports for twining — netting, string, wire, or small trellises. The vine will also scramble through other plants.

Container Growing: Excellent in containers — use a good potting mix and a trellis in the pot. Great for hanging baskets where the vine trails and blooms.

Deadheading: Remove spent flowers to encourage continued bloom and prevent self-seeding in areas where this is a concern.

Hardiness: USDA Zones 10–11 as a perennial. Grown as an annual elsewhere.

Propagation: Primarily by seed. Cuttings root easily in warm weather.