Quick Facts

Quick facts

  • Sagittaria (Sagittaria platyphylla) is an emergent aquatic perennial to 1.2 m tall, and is distinguished by lance-shaped adult leaves, and white 3-petalled flowers.
  • It is becoming increasingly common in irrigation supply channels, drains, shallows creeks and wetlands, in New South Wales, Victoria and Queensland.
  • Sagittaria is spread mainly by rhizomes, tubers and seeds, which increase the area of existing colonies.
  • It is an important weed of rice crops and wetlands in the eastern states, and is a threat to waterways and wetlands across Western Australia, especially to the Ord River Irrigation Area.
  • It can be controlled with the use of herbicides.

What Does It Look Like?

What is it?

Sagittaria (Sagittaria platyphylla) is an emergent aquatic perennial to 1.2 m tall, rooted in the swamp floor and reproducing by seeds, rhizomes (underground stems) and tubers. The stems are triangular in cross-section. The submerged leaves are translucent and strap-like, to 50 cm long. The emergent leaves (those rising out of the water) are lance-shaped to 28 cm long and 10 cm wide, on a long stalk.

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

The fruit is a cluster of 1-seeded segments, each segment flattened, winged and 1.5-3 mm long (Parsons & Cuthbertson 2001; Thorp & Wilson 1998 -; Department of Agriculture and Food undated).

For further information and assistance with identification of Sagittaria contact the herbarium in your state or territory.

Flower colour

White, Pink

Growth form (weed type/habit)

Herb, Aquatic

Where it currently grows? Preferred habitat

Sagittaria is becoming increasingly common in irrigation supply channels, drains, shallows creeks and wetlands. It is shade tolerant and forms dense patches, obstructing water flow and producing luxuriant growth in enriched conditions (Thorp & Wilson 1998 -).

Are there similar species?

Sagittaria can be confused with other species of Sagittaria and Alisma lanceolatum. Alisma lanceolatum also has emergent lance-shaped leaves on long stalks but it doesn't have the submerged strap-like leaves of Sagittaria. Sagittaria and Arrowhead (S. montevidensis) can be distinguished by their leaf shape. Sagittaria has lance-shaped emergent leaves whereas those of Arrowhead are broadly arrow-shaped with spreading basal lobes (Parsons & Cuthbertson 2001; Sainty & Jacobs 2003).

Why Is It A Weed?

What are its impacts?

Agriculture: Sagittaria is an important weed of rice crops and wetlands in the eastern states, and is a threat to waterways and wetlands across Western Australia, especially to the Ord River Irrigation Area. It blocks water flow in irrigation canals and drainage ditches thus raising production costs.

Native ecosystems: It competes vigorously with native water plants (Thorp & Wilson 1998 -; Department of Agriculture and Food undated).

How does it spread?

Sagittaria is spread mainly by rhizomes, tubers and seeds, which increase the area of existing colonies. Most seeds drop within the parent colony but may be eaten by birds and excreted elsewhere. Also, entire plants may break away, float downstream and establish elsewhere (Parsons & Cuthbertson 2001; Thorp & Wilson 1998 -).

What is its history in Australia?

The method and time of introduction of Sagittaria into Australia is unknown but it was first recorded as naturalised in the Ekibin Creek, near Brisbane, in 1959. In 1962, it was found naturalised in Nine Mile Creek in Victoria and in 1964, in two locations in New South Wales (Parsons & Cuthbertson 2001).

How To Manage It?

Best practice management

Chemical control: The use of herbicides is more likely to be effective in Australia (Parsons & Cuthbertson 2001).

Non-chemical control: In some countries, Sagittaria has been controlled by winter ploughing of stream, canal and lake beds after irrigation has ceased and the water drained, thus exposing the tubers and rhizomes to frost and desiccation.

Biological control: The NSW Environmental trust is co-investing in a multi-investor independent project on the deployment of a new biocontrol agent for sagittaria, based at Agriculture Victoria Research Division, Department of Jobs, Precincts and Regions, Victoria and in collaboration with NSW Department of Primary Industries (CSIRO; Kwong 2020). The project will undertake releases and evaluation of the fruit-feeding weevil Listronotus appendiculatus for biocontrol of sagittaria in southern NSW and northern Victoria. This biocontrol agent was recently approved for release in Australia by the relevant authorities. The first part of the project (April – Sept 2021) will focus efforts on developing an efficient and effective mass rearing protocol for the weevil. Releases and evaluation will occur between October 2021 and June 2023 (CSIRO; Kwong 2020).

More information can be found here https://research.csiro.au/nswweeds/sagittaria/

Please see the Australian Pesticides and Veterinary Medicines Authority for chemical information http://www.apvma.gov.au 

Does it have a biological control agent?

YES.  The fruit-feeding weevil Listronotus appendiculatus was approved for release in 2020 (Kwong 2020).  Program undergoing release phase (Harvey et al 2023)

When does it grow? (lifecycle/growth calendar)

Seeds of Sagittaria germinate in spring and rhizomes start forming about a month afterwards. The rhizomes grow slowly, producing tubers. Flowering occurs from January to late autumn, with fruit maturing during autumn and early winter. Rhizomes and tubers become dormant in winter and buds start shooting in spring (Parsons & Cuthbertson 2001).

Where Is It Found?

Which states and territories is it found?

NSW, QLD, SA, VIC, WA

What areas within states and territories is it found?

Sagittaria is now widespread and common in northern Victoria, south-western New South Wales, around Sydney and Newcastle, and south-eastern Queensland (Thorp & Wilson 1998 -). In Western Australia it has been found in the Canning River in Perth and at Albany (Department of Agriculture and Food undated). In 1981, Sagittaria was found along parts of the Murray River in South Australia, but had largely disappeared by 1985. It is thought that carp and spoonbills feeding on the plants may be responsible for this disappearance, but this is not known with certainty (Parsons & Cuthbertson 2001).

Where does it originate?

Sagittaria is a native of North America down to Panama and has been introduced to many countries as an ornamental aquatic (Parsons & Cuthbertson 2001).

National And State Weed Listings

Is it a Weed of National Significance (WONS)?

YES

Where is it a declared weed?

NSW, SA, TAS, WA

Government weed strategies and lists – Weeds Australia

Is it on the National Alert List for Environmental Weeds?

NO

Government weed strategies and lists – Weeds Australia

Is it on the Agricultural Sleeper List?

NO

Government weed strategies and lists – Weeds Australia

Names And Taxonomy

Main scientific name

Sagittaria platyphylla

Other scientific names (synonyms)?

  • Sagittaria graminea var. platyphylla Engelm.
  • Sagittaria graminea var. weatherbiana (Fernald) Bogin
  • Sagittaria weatherbiana Fernald
  • Sagittaria graminea Michx. (misapplied by Conn, B.J. 1994, Flora of Victoria Edn 1. 2: 129, Fig. 27j-m.)

Does it have other known common name(s)?

Arrowhead, Delta Arrowhead, Slender Arrowhead

National Best Practice Manual

file Sagittaria (Sagittaria platyphylla) National Best Practice Management Manual 2023
Sagittaria is a significant threat to waterways and irrigation systems in Australia. The weed has been present in Australia since the late 1950s, having been introduced as an ornamental pond plant. Since its introduction to Australia, sagittaria has infested hundreds of hectares of waterways and irrigation channels and is continuing to spread into areas where it was previously unknown. It has been recorded in every state and territory in Australia except Tasmania.

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