Sagittaria

Sagittaria is a declared Class A and Class C weed and a Weed of National Significance. 

Another name for this plant is Sagittaria platyphylla.

If you think you have seen a plant that looks like sagittaria, have it growing on your property or have recently bought a plant that resembles sagittaria, don't attempt to control it or dispose of it. Contact the Weed Management Branch immediately for help.

To find out more about sagittaria go to the Weeds of National Significance website.

Watch the sagittaria video on youtube.

Identification

You should use this as a guide. There may be other plants or weeds that look similar.
If you are unsure, contact the Weed Management Branch.

Habit

Sagittaria weed

These features describe the habit of this plant:

  • aquatic plant rooted in the ground
  • can grow submerged or emerging above the water surface
  • fast growing perenial
  • up to 1.2m tall
  • reproducing by seeds, rhizomes and tubers.

Stems and branches

Sagittaria stems and branches Sagittaria stems

The stems of sagittaria are triangular-shaped in cross-section.

Leaves

Sagittaria leaves Sagittaria leaves

These features can identify the leaves:

  • submerged leaves are translucent and strap-like
  • submerged leaves are up to 50cm long
  • emergent leaves are lance-shaped
  • emergent leaves are up to 28cm long and 10cm wide
  • emergent leaves are on a long stalk.

Flowers

Sagittaria flowers 

These features can identify the flowers:

  • white, or sometimes pink
  • appear at the top of a leafless stalk
  • always below leaf height
  • in 2 to 12 whorls of three flowers arising from the same position on the stem
  • male flowers are at the top and female ones at the bottom
  • both male and female flowers have 3 petals.

Fruit and seeds

Sagittaria fruit and seeds © User:Show Ryu / Wikimedia Commons / CC-BY-SA-3.0 Sagittaria fruit and seed

These features can identify the fruit and seeds:

  • fruit is a cluster of one-seeded segments
  • each segment flattened, winged and 1.5mm to 3mm long.

Similar looking plants

There are several aquatic and semi-aquatic plants that look similar to sagittaria. If you think you have seen a plant that may be sagittaria, contact the Weed Management Branch for help. If you have any doubt about the identification of the plant, contact the Weed Management Branch.

In particular, the plant species Echinodorus looks similar to sagittaria.  There are several varieties of Echinodorus - including Echinodorus subalatus and E. longiscapus - growing and being sold in the Darwin region. They look similar to sagittaria but are not considered weeds.

Impact

Sagittaria is an important weed of rice crops and wetlands in the Eastern States.

It is a threat to waterways and wetlands across Western Australia, especially to the Ord River Irrigation Area.

It is becoming a problem in irrigation channels, drains, creeks and wetlands, where it forms dense patches which obstruct water flow.

Sagittaria can have the following impacts:

  • dense infestations can reduce water flow
  • blocked irrigation channels can increase production costs
  • blocks natural waterways and chokes out native vegetation
  • may restrict access for recreational fishing, boating and swimming.

Habitat and distribution

Sagittaria is native to North America and was introduced to many continents as an ornamental plant.

It is not known how or why sagittaria was first imported into Australia.

It was first discovered naturalised near Brisbane in 1959, then in 1962 in Victoria and in 1964 in New South Wales.

It now occurs along the East Coast of Australia as far north as Cairns.

It is common in northern Victoria, south-eastern New South Wales and south-eastern Queensland.

It has been found in isolated locations around Adelaide, South Australia, and at Perth and Albany in Western Australia.

Sagittaria is not known to occur in the NT.

Spread prevention

Sagittaria is a prolific seed producer. Seeds are tiny and can be spread by water or by attaching to water birds. If you have sagittaria on your property, and especially if it is flowering or seeding, contact the Weed Management Branch immediately for urgent help.

Control

If you think you may have seen sagittaria, or have this weed on your property, do not attempt to control it.

Contact the Weed Management Branch immediately for assistance.

Sagittaria is on the alert list for environmental weeds.  This is a list of weeds that threaten biodiversity and cause other environmental damage.

Last updated: 27 June 2017