Weed Alert: Water soldier
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Contacts and Further InformationIf you find this weed please contact your local Council Weeds Officer or the nearest NSW Department of Primary Industries office immediately for positive identification and further assistance.
Alternatively call the NSW Weeds Hotline on
1800 680 244 or send an email to email@example.com
Water soldier (Stratiotes aloides)
Water soldier is an emergent aquatic plant that has the potential to become a serious weed of freshwater lakes, ponds and dams in Australia. It is a plant with vigorous growth that forms dense stands in suitable conditions. These dense stands can exclude native wetland plants and destroy aquatic habitats.
Water soldier leaves resemble aloe plants, and as such it is also called water aloe.
Water soldier has an unusual growth habit. It is a submerged plant except in summer when it rises to the water surface to flower. The new leaves that grow in spring contain air pockets allowing the plant to float. As the older leaves die back in autumn they become waterlogged which causes the plant to sink again.
Water soldier can remain submerged all year round and can grow in depths of up to 5 m.
Water soldier is not currently found in New South Wales (NSW) or elsewhere in Australia.
Water soldier is a native of Europe. It has become a serious pest in other countries after being introduced for aquariums and outdoor ponds.
Water soldier can reproduce vegetatively and by seed. It spreads mostly by vegetative reproduction in summer when lateral shoots produced at the base of the plant break away to form new rosettes. Up to eight or ten rosettes can form in a circle around the parent plant, filling the water column and preventing all other plants from growing.
To reproduce by seed, male and female plants need to be growing in close proximity. Each rosette forms a single flower stem in summer. The seed capsule becomes submerged at the end of summer as the plants sink, allowing seeds to float downstream.
Water soldier plants have a distinct appearance in that individually they resemble the top of a pineapple.
Key identification features
- Leaves extend from a rosette, are long and narrow with a slightly triangular shape. Submerged leaves are light green and up to 60 cm long with little spines along the margins. Emergent leaves are a dark green, less than 40 cm long and 1–4 cm wide with well-developed spines along the margins. The leaves are very brittle.
- Little is known about the conditions required for flowering in this species. The flower stalk is short and thick, and about 15 cm long. At the top of the stalk is a two-leaved sheath, like the claws of a crab. The sheath contains several delicate white flowers, with three petals and numerous stamens. The flower develops into a pulpy, flask-shaped berry.
- Roots either hang free in the water or, more usually, are loosely rooted in the mud.
Contact your local council weed officer for assistance with removal and control if you suspect you have found water soldier.
Water soldier is a Class 1 State Prohibited Weed across NSW under the Noxious Weeds Act 1993. It must be eradicated and land must be kept free of the plant. As a notifiable weed, all outbreaks must be reported to the local council within 24 hours, and the plant is prohibited from sale in NSW.
2005 edition prepared by Annie Johnson; 2013 edition prepared by Elissa van Oosterhout; Technically reviewed by Rod Ensbey.
Cook CDK and Urmi-Konig K (1983) A revision of the genus Stratiotes (Hydrocharitaceae), Aquatic Botany, 16:213–249.