Hygrophila

Native to Mexico and Argentina, hygrophila is a flowering, erect herb that grows on creekbanks and in shallow freshwater wetlands.

Hygrophila has now naturalised in New South Wales, and is an emerging problem for Queensland's waterways. The main danger is that aggressive hygrophila growth will pose a competitive threat to native water plants.

Hygrophila is a restricted invasive plant under the Biosecurity Act 2014.

Scientific name

Hygrophila costata

Other names

Gulf swamp weed, glush weed

Description

  • Erect, emergent herb up to about 1m tall.
  • Leaves opposite, simple, 3-18cm long, 1-5cm wide, oblong to elliptic, coarse in texture, with prominent veins and distinct midrib.
  • Papery, white flowers, 9-11mm wide, produced in clusters where leaf joins stem.
  • Spreading stems sprout new roots from nodes where they contact soil.
  • Larger stems can be quite robust.
  • Fruit is a 2-valved capsule, 14-17mm long.
  • Each capsule has 12-18 seeds.
  • Seeds are pale brown, round, flattened, smooth, 0.3-1mm long.

Habitat

  • Found along creekbanks and in shallow, freshwater wetlands.

Distribution in Queensland

Infestations found at:
  • Lake Macdonald, 15km south-east of Cooroy (first collected in 1993; several thousand noted at site by 1999)
  • Caboolture River, approximately 0.5km south of Caboolture (1995)
  • Four Mile Creek, Strathpine (1996)
  • Beenleigh, Hugh Muntz Park (1997)
  • Cedar Creek, Mt Tamborine - scattered clumps
  • Albert River (at junction of Cedar Creek) - 1 small clump
  • Coomera River and Beaudesert (small infestations)
  • Russell River, Babinda (2007)
  • coastal Queensland (small infestations).

Life cycle

  • Flowering and fruit production occurs from December-March.

Impacts

Environmental

  • Grows aggressively and competes with native water plants.
  • Forms mats of dense, floating growth at the edges of freshwater lakes.

How it is spread

  • Can spread by floodwaters.

Control

Herbicide control

Legal requirements

  • Hygrophila is a restricted invasive plant under the Biosecurity Act 2014.
  • It must not be given away, sold, or released into the environment without a permit.
  • The Act requires everyone to take all reasonable and practical steps to minimise the risks associated with invasive plants and animals under their control. This is called a general biosecurity obligation (GBO).
  • At a local level, each local government must have a biosecurity plan that covers invasive plants and animals in its 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.

More information