Sagittaria

Native to North America, sagittaria is an aquatic perennial introduced to Australia as an aquarium plant. In the wild, it invades and degrades natural wetlands. The first infestation of sagittaria was found in Brisbane in 1959, then Victoria in 1962. It is now widely distributed in the Murray Irrigation District, Sydney and Newcastle, Melbourne, Perth, Canberra, and Adelaide.  It is a Weeds of National Significance.

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

Scientific name

Sagittaria platyphylla

Description

  • Emergent aquatic perennial up to 1.5m tall.
  • Leaves are oval/linear shape with pointed tips, up to 25cm long and 10cm wide at the top of each leaf stalk, also narrow strap-like submerged leaves up to 50cm long.
  • Stems are triangular in cross-section.
  • Flowers appear in whorls or coils.
  • Male flowers are 3cm across with 3 white petals, yellow centers.
  • Female flowers have no petals, resembling flattened green berries.
  • Flowers appear below the height of the leaves.
  • Seeds are clustered, consisting of flattened and winged segments, 0.15-0.3cm long, 1 seed in each segment.
  • There are 3 morphological growth forms: submerged rosette, broad-leaved emergent and narrow-leaved emergent. These forms play an important role in the life cycle allowing the species to adapt to varying environmental conditions.

Habitat

  • Grows in irrigation channels, drains, creeks, rivers, lagoons, dams and wetlands.
  • Establishment favoured by slow moving or static shallow water.

Distribution in Queensland

  • Found in South East Queensland, Mackay and around Cairns.

Life cycle

  • Can reproduce via several methods. It is a prolific seeder, with each plant having the ability to produce hundreds of thousand seeds.
  • Seed production occurs from September-May.
  • Germination can occur anytime the conditions are favourable.
  • It can reproduce vegetatively by stem or root fragment.
  • It can reproduce from underground rhizomes and corms.

Impacts

Environmental

  • Forms floating mats, blocking irrigation ditches, shallow dams and waterways.
  • Invades and degrades natural wetlands.
  • Competes with native water plants.

Economic

  • Blocking irrigation of crops.

How it is spread

  • Spread through cultivation and sale as an aquarium or ornamental water plant, and through dumping of aquarium contents into waterways.
  • Spread by broken stem, leaf fragments and seed.
  • Seeds spread by water, and in soil on vehicle tyres, animals and birds.

Control

Control is best carried out when water levels are low. Appropriate hygiene and containment measures need to be applied to prevent further spread downstream.

Mechanical control

  • Place all removed plant material in sealed plastic bag, leave in sunlight to decompose, then dispose of at council-approved landfill tip. Alternatively, leave material in sun to dry, then burn.
  • Do not leave broken plant pieces in growth area.

Herbicide control

  • Biosecurity Queensland has a minor use permit from the Australian Pesticides and Veterinary Medicines Authority for herbicides suitable for use.

See the for the WONS sagittaria management guide for herbicide control and application rates.

Biological control

  • No know biological control agents.

Legal requirements

  • Sagittaria 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