Weed of the Month


Gomphocarpus fruticosus

Cottonbush (Gomphocarpus fruticosus) is an upright shrub originating from South Africa.  The seeds are light and dispersed by the wind.  Narrowleaf Cottonbush is a declared pest plant in Western Australia and can form dense thickets, which is a bushfire risk.  It is important to wear gloves, long sleeve shirt, long pants and closed in shoes for handling Cottonbush, as the sap can irritate exposed skin. The shallow root system means small infestations can be dealt with by hand pulling. If the plant has mature fruits they should be bagged and cut off first, as disturbing the fruit can release the seeds which will travel on the wind.  All material, especially seeds and seed pods, should be removed and disposed of carefully to prevent further spread.  Larger infestations are best managed with a combination of mowing or brush-cutting, followed up by targeted spraying with glyphosate. Herbicide is best applied in spring to early summer when the plant is actively growing.


In late summer and autumn, limit the release of seeds if you can and make a note to go back in spring.  Florabase has a Management Calendar and recommends foliar spray with 1.5% glyphosate or try cut and paint using 50% glyphosate (before flowering gives better results) – see https://florabase.dpaw.wa.gov.au/browse/profile/6587

This weed was featured in the latest edition of the Greenpage newsletter.