Macquarie Valley Weeds Committee & Lachlan Valley Weeds Advisory Committee

Water Lettuce

Botanical Name:

Pistia stratiotes

Other Common Names:

Declarations

Class	Regions
Class 1	All Of N.S.W.

Landholder Responsibilities:

The plant must be eradicated from the land and the land must be kept free of the plant

Why Is It Bad?:

Water Lettuce is a weed in the sub-tropical areas of the State. It is free-floating and can quickly cover an entire body of water. It can reproduce vegetatively and by seed. It is currently feared that recent floods in Queensland and northern New South Wales will spread Water Lettuce into the Darling River system.

Identification

Habit:

Water Plant

Leaves:

Leaves are light green, 2.5-15cm long and up to 8cm wide. They are fan shaped with 6 or more prominent veins and covered with short white hairs which help to keep the plant afloat.

Flowers:

Flowers are only small and are produced at the base of the leaves. They are white, 7-12mm long and 5mm wide.

Fruit:

Produces a berry-like fruit, 5-8mm wide

Roots:

Roots are long and feathery. 80cm long.

Control Methods

Manual Removal:

Plants must be physically removed from the water and dried. Removed plants should not be within the flood zone or near mud as they may take root.

Chemical Use:

Herbicide use is often less expensive than manual removal. Autumn is considered the best time for application. See the Noxious & Environmental Weed Control Handbook for recommended chemicals and rates. Appropriate safety measure must eb considered when using herbicides in or near waterways.

Fire:

Slashing & Cutting:

NOT RECOMMENDED. Any cutting or slashing of the plant will cause daughter plants to break off and spread to new sites.

Biological Control:

The weevil Neohydronomus affinus is used in Queensland but has not been introduced in NSW.

Grazing:

Cultivation & Scalping:

Smothering:

Solarisation:

Competition:

Monitoring:

Successful treatment programs rely on ongoing monitoring of sites. Missed plants can easily become larger infestations if follow-up treatments are not part of the management program

Images

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Image Credit: Don Mackenzie