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Black-eyed Susan

Botanical name: Thunbergia alata
Environmental Weed

Black-eyed susan

 

 

 

 

 

 

 

 

 

 

Description

Thunbergia alata, commonly called Black-eyed Susan, is a slender vine that grows about 4m long. It is native to Eastern Africa, and has become an invasive weed species in Australia.

Flowers are bright yellow-orange, with a striking black centre. Flowers have five petals and grow on a long stalk. Leaves are roughly triangular to heart-shaped, with soft fine hairs and broadly toothed margins. Roots form at the nodes of the stem when they come into contact with the soil, anchoring the plant and forming new plants.

Dispersal

Black-eyed susan is probably pollinated by bees. The flowers reflect ultra violet light in a pattern that is visible to insects but not to humans. This helps insects find the centre of the flower. Seeds are perhaps ejected mechanically when the fruit splits open.

Impact on bushland

Black-eyed susan can spread from gardens into bushland and be of huge threat to native vegetation.

Control

Hand-pull or dig young plants, or spray larger plants.

Similar species

Many climbers have heart-shaped leaves, including natives and other weeds, but the leaves of black-eyed susan are thinner textured or paler than those of most other such climbers and the hairy surface is distinctive. The orange and black flowers are unmistakeable.

Good non-invasive native alternatives to black-eyed Susan are snake vine (Hibbertia Scandens) and native sarsaparilla (Hardenbergia violacea).