Biosecurity Spotters logo

Hygrophila (Hygrophila costata)

Hygrophila is a serious weed of waterways in coastal New South Wales and south-eastern Queensland, where it forms dense mats that can displace native plants. It also disrupts habitat for local fauna and can spread from aquarium plant disposal into waterways.

Key facts

Type: Weed, aquatic.

Native to: North, Central and South America.

Established in: QLD, NSW.

Other names: Lake Hygrophila, Glush Weed, Gulf Swampweed, Temple Weed.

Identification

  • This aquatic herb grows to 90 cm high.
  • Its stems are four-sided and grooved lengthways, and may be hairless or hairy.
  • The oval leaves have very short stalks, short-pointed tips, and grow up to 90 mm long and 20 mm wide.
  • Clusters of 10 or more white, tubular flowers grow on very short stalks.
  • Its narrowly oval capsules are 6–8 mm long and contain about 20 seeds.
  • Look-alike: The native Hygrophila angustifolia is smaller (15–45 cm), has narrower leaves (2–8 mm wide) and larger fruit (10–18 mm long).
  • Look-alike: Senegal tea plant (Gymnocoronis spilanthoides) has somewhat hollow stems and finely toothed leaves; Dyschoriste depressa has bristles at the base of the male reproductive parts and fruits containing only four seeds.

Where it grows

In Australia it occurs in waterways, lakes, dams, ponds and wetlands, and has naturalised in south-eastern Queensland and north-eastern New South Wales.

Why it matters

  • It grows aggressively and forms dense mats in shallow water and adjacent damp soils.
  • These mats can displace and out-compete most other native species.
  • It disrupts habitat for local fauna.

How it spreads

  • It was almost certainly introduced as an aquarium plant and became naturalised after aquarium contents were disposed of into local rivers.
  • Sticky seeds can adhere to animals, machinery and watercraft.
  • Plants can also spread locally through rooting nodes.

Control options

  • Hand removal is beneficial for isolated plants, but large-scale removal may damage native vegetation or aquatic ecosystems.
  • Carefully handle and bag all plants and plant parts, as new infestations can form from pieces left behind.
  • Some herbicides are effective, but take care when using them near waterways; consult the APVMA for chemical information.
  • Planting large shading trees can reduce growth through shade and competition, and preventing animal or mechanical access to infested areas can reduce spread.

Hygiene and washdown

  • Sticky seeds can adhere to machinery and watercraft, so check these for plant material before moving them from infested areas.
  • Prevent animal or mechanical access to infested areas to reduce the spread of seeds and other plant parts.
  • Inspect and clean vehicles, plant and footwear before leaving an infested area, paying attention to tyres, radiators, belly plates, tracks and floor mats.
  • Wash down at a designated bay where runoff is contained and can be monitored for seedlings.
  • Record each washdown so the client has evidence of clean entry and exit.

Classification by state

  • Australia (national): No national listing. Managed under state and territory law.
  • Queensland: Restricted matter, category 3. Do not give it away, sell or release it into the environment. Everyone must also take all reasonable and practical steps to minimise its risks (the general biosecurity obligation).
  • New South Wales: Regional priority in 4 of 11 regions. Regional priority weed in Central West, Greater Sydney, Hunter, North West. The general biosecurity duty applies: anyone dealing with it must prevent, eliminate or minimise the risk it poses.
  • Victoria: Not declared. Not declared under the Catchment and Land Protection Act 1994. Other Victorian laws may still apply.
  • South Australia: Not declared. Not declared under the Landscape South Australia Act 2019. Other laws may still apply.
  • Western Australia: Permitted, not declared. Listed as a permitted organism in WA, so it can be brought in, but it is not a declared pest.
  • Tasmania: Not declared. Not a declared weed in Tasmania. Other laws may still apply.
  • Northern Territory: Not declared. Not on the NT A to Z weed list, and Weeds Australia does not list it as declared in the NT. Check the NT declared weeds list before moving or planting it.
  • Australian Capital Territory: Not declared. Not declared under the Biosecurity Act 2023 (ACT). A general biosecurity duty still applies.

Legal obligations

Every state and territory places a duty on landholders and people working on land to prevent the spread of invasive species, such as the general biosecurity obligation in Queensland and the general biosecurity duty in New South Wales. Declarations and control requirements differ between states and local government areas, so check the current official list before work starts.

  • Queensland: Biosecurity Act 2014 (Qld), administered by Biosecurity Queensland (13 25 23)
  • New South Wales: Biosecurity Act 2015 (NSW), administered by NSW Department of Primary Industries and Regional Development

Sources