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Siam Weed
Botanical name: Chromolaena odorata
Noxious Weed Category: Class 1
Special note: Notify your local weeds officer of sightings immediately. Pollen and contact with the plant can cause hayfever and skin rashes in some people. This plant is toxic to stock.
Source: NSW Agriculture : WEEDdeck 1999
Description
Also known as Chromolaena.
Originating in Central America, Siam Weed is a soft green perennial bush. It produces densely tangled bushes up to 7m tall when growing in the open or supported by another plant or object. As a climber it can reach 20m. The stems can grow up to 7m long. The soft pithed stems are succulent at the tip and woody at the base. Dies back to the crown in dry periods, re-shooting again after rain.
Leaves are triangular shaped, 5 - 7 cm long with forward facing serrations. When crushed leaves have a slightly sweet pungent smell. Masses of bluish pale mauve tubular flowers with up to 70 florets grouped into bell shaped heads. Flowering occurs in winter. Seeds are brown to blackish 4 to 5mm long. At maturity, each seed has a 5mm white pappus (parachute white hairs at the end of the seed) attached.
Dispersal
Siam Weed may be spread long distances by wind and water. Seed is also moved in mud on machinery and recreational vehicles.
Impact on bushland
It is widespread throughout tropical and subtropical lands and the potential for spread includes down the NSW coast and south of Sydney.
Control
Chemical: Please contact your local control authority for advice on chemical control.