Family: Alismataceae

Status:

Description:
Sagittaria is a tufted perennial herb to about 80cm high that grows around the water’s edge. It will survive variation in water levels, either flooding or extensive dry periods. It has two types of leaves: submerged long narrow strap-like leaves and emergent large spoon shaped leaves with a pointed tip. Stems are triangular in cross-section. Male flowers are quite showy, with 3 white petals, to 3cm across. They are carried in whorls on an erect stem, above the female flowers which have no petals and look rather like a flattened green strawberry.

Preferred habitat and impacts:
On mud around the edges of fresh water bodies.
Can displace native water plants which occupy the same habitat.

Dispersal:
Dumping of aquarium or ornamental pond plants is often the means of spread for aquatic weeds. Probably also spread by seed which can adhere to the feathers or feet of water birds, and hence be spread long distances.

Look-alikes:
It is similar to the introduced blue-flowered pickerel weed (Pontederia cordata), and to the white-flowered native water plantain (Alisma plantago-aquatica). Sagittaria can be distinguished from water plantain by the following features: having submerged strap-like leaves as well as emergent spoon-shaped leaves, having only one main mid-vein on the emergent leaves (rather than a mid-vein and several prominent parallel veins), having larger flowers (3cm diameter compared with 1cm in water plantain).

Control
Most importantly, do not dump unwanted aquatic plants into or around water bodies, or grow species with weed potential in ornamental ponds. Once an infestation is established, and has been definitely identified, there are two options, mechanical or chemical control. Plants growing around the water's edge, such as sagittaria, can be dug up. For large infestations, herbicide may be necessary, but a permit will be required from the Environmental Protection Agency to apply any herbicide to a water body. Only a limited number of herbicides are registered for use over water. If you suspect you have an outbreak of an aquatic weed, notify your local weed control authority (usually Council) and take their advice on control methods.