Weed Identification

Australia > > Salvinia

Salvinia

Salvinia molesta

THIS PLANT HAS BEEN DECLARED A WEED OF NATIONAL SIGNIFICANCE

Family: Salviniaceae.

Form: Water plant

Origin: Southern Brazil and Paraguay.

Description: Free-floating, mat-forming perennial. Individual plants 5–30 cm long, with 'leaves' (fronds) in whorls of 3 at each node, consisting of a pair of floating leaves and a submerged modified leaf that looks like and functions as a root. Upper surface of leaves covered with waxy egg-beater-shaped hairs; lower surface of leaves and root-like leaf covered with dark hairs. Fruiting bodies containing sterile spores hang from the divided leaf. Appearance varies depending on degree of crowding and availability of nutrients. The primary form occurs as isolated plants with small oval leaves that lie flat on the surface. The tertiary form is when plants multiply and become crowded; leaves are up to 6 cm wide.

Distinguishing features: Distinguished from other species of Salvinia by its egg-beater-shaped hairs on the upper 'leaf' surface.

Dispersal: Does not produce fertile spores. Reproduces by fragmentation.


Mature 'leaves' & sterile sporocarps

Notes: Often survives for a short time after being stranded by receding waters. In nutrient rich water where temperatures are optimum, it is capable of doubling in area in less than 5 days. Prolific growth is a good indicator of the nutrient status of the water. A serious weed that will choke and cover wetlands and lakes, excluding fish and invertebrates. The Salvinia weevil, Cyrtobagous salviniae, provides effective control under certain conditions.

References:

    Waterplants in Australia. G. Sainty and S. Jacobs, 3rd edition, 1994, pages 12–13. Noxious Weeds of Australia. W. Parsons and E. Cuthbertson, 1992, pages 18–22. The Biology of Australian Weeds. R. Groves et al. (eds), Vol. 1, 1995, pages 217–230.

Web References: Search Australian web sites for further information on this weed.

The secondary growth
form of Salvinia
Infestation amongst trees in Kakadu National Park
Weevils, Cyrtobagous
salviniae, feeding

This weed has been included in the WEEDeck field guide as card W02

More information about WEEDeck is available from Sainty & Associates Pty. Ltd.

 

Australia > > Salvinia

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