Know Your Weeds - South African Weed Orchid

South African Weed Orchid, Disa bracteata, is an aggressive ground-orchid originating from South Africa. It is spreading rapidly across Victoria and has been found at multiple sites across the Surf Coast Shire and adjoining municipalities.

South African weed-orchid flowers

South African weed-orchid rosette

South African weed-orchid tubers

Capable of growing in both shade and open ground, it can establish under a moderate canopy. Generally grows in disturbed areas and can be found in woodlands, heathlands, roadsides, grazing lands with the capacity to invade bushland and pastures.

Flowers range from green/yellow, reddish-brown, arranged in a dense spiral on a fleshy stem growing to 30cm. Emerging flower stalk looks like a thick stem of asparagus. Growth rate exceeds most other species of the same life form.

Disa is capable of sexual and vegetative reproduction, is capable of self-pollination, and has tubers.

Known to be both wind and water dispersed, it is likely to be introduced accidentally on vehicles and machinery, spread by seeds on clothing, shoes and camping equipment. Seeds are minute and dust-like and may be blown many kilometres.

First detected in Victoria in 1994, Disa populations have been detected in around 50 locations across Victoria. The orchid can germinate in the presence of a wide range of fungal partners, especially those which thrive on disturbed soil.

Weed Management

Management of Disa bracteata is primarily by digging out and bagging the plant and tubers in an air-tight bag to avoid further distributing the fine seed. Further monitoring of infested sites in spring is vital to ensure any missed plants are caught before seeding in October. Spot-spraying rosettes before flower stem emergence. Blanket spraying is not recommended as Disa is a coloniser and thrives in cleared areas.

Chemical control trials of wiped herbicide have been carried out and are described in the Autumn 2016 Landcare magazine.