Black-eyed Susan

Black-eyed Susan is a species of Thunbergia, which are vigorous, perennial, twining vines native to northern India and tropical Africa.

Black-eyed Susan takes its name from the black centres of its striking yellow-orange flowers. A popular garden species, black-eyed Susan can smother native vegetation if it spreads into native bushland. It has become common in coastal regions of Queensland and in eastern New South Wales.

Black-eyed Susan is not a prohibited or restricted invasive plant under the Biosecurity Act 2014.

Scientific name

Thunbergia alata

Similar species

  • Thunbergia spp.

Description

  • Slender-stemmed vine up to about 4m long.
  • Leaves are pale green, paired, roughly triangular to heart-shaped, 3-4cm long, with soft fine hairs and broadly toothed margins.
  • Flowers are bright yellow-orange, with striking black centre 3-4cm wide, 5 petals, on long stalk.
  • Seed capsules are round to a beak, 6-8mm, burst open to shoot out seeds.
  • Seeds are brown, shiny, round, 4mm.
  • Roots form at nodes of stem when they come into contact with soil, anchoring plant and forming new plants.

Habitat

  • Grows along waterways, in urban bushland and on forest margins.

Distribution

  • Found along coast from north Queensland to New South Wales border.

Life cycle

  • Flowers throughout year, mostly in spring and summer.

Impacts

Environmental

  • Can spread from gardens into bushland, threatening native vegetation.

How it is spread

  • Spread by seed and vegetatively by fragments of stems and roots, generally in dumped garden waste.

Control

Physical control

  • Hand-pull roots.
  • Mulch heavily to prevent regrowth.

Herbicide control

  • No herbicide is currently registered in Queensland; however, off-label use permit (Permit No. PER11463) allows use of various herbicides for control of environmental weeds in non-agricultural areas, bushland, forests, wetlands, and coastal and adjacent areas.

Biological control

  • No known biological control agents.

Legal requirements

  • Black-eyed Susan is not a prohibited or restricted invasive plant under the Biosecurity Act 2014. However, by law, everyone has a general biosecurity obligation (GBO) to take reasonable and practical steps to minimise the risks associated with invasive plants and animals under their control.
  • Local governments must have a biosecurity plan that covers invasive plants and animals in their area. This plan may include actions to be taken on certain species. Some of these actions may be required under local laws. Contact your local government for more information.

Further information