History of the Problem

Ornamental Garden Plant

Many older residents in the Maldon district believe the first Wheel Cactus (Opuntia robusta) was planted in our area in the mid 1900’s, most likely as an ornamental garden plant. This cactus is not a native Australian plant but is introduced from Mexico.  There are reports of earlier sightings in our local district, however these may have resulted from confusing the Wheel Cactus plant with other closely related and common cacti, such as Prickly Pear (Opuntia stricta) and Riverina Pear (Opuntia elata). These cacti have been planted in many house gardens since the Gold Rush era of the 1850’s, but have not spread far beyond their original locations and not developed into a devastating noxious weed like Wheel Cactus.

Rapid Invasion

Wheel Cactus is particularly suited to rocky granite environments; hence the plant has rapidly invaded the granite hills surrounding the Maldon township, Mount Tarrangower, Pigeon Hill and The Nuggettys.

The foremost vector in spreading Wheel Cactus is the common crow, the Australian Raven (Corvus coronoides). This bird has a long beak and can eat the attractive red fruit without being injured by the long prickles covering the lobes. These birds feed very happily on the juicy fruit, each containing approximately 500 seeds. Large flocks of juvenile ravens feed on Wheel Cactus fruit and can fly up to a 20 km radius, spreading the seeds in their droppings. Emus can also feed on the fruit and the Red Fox (Vulpes vulpes) will eat fallen fruit, adding to the dispersal of the seeds.

By the 1960’s, Wheel Cactus was already spreading uncontrollably in the Maldon area and the species was registered as a Noxious Weed within Victoria. An article in the local ‘Maldon Times’ highlights that this cactus was already a serious problem in 1963. Maldon Times May 13 1963 Maldon Times May 13 1963. Within 30 years, around the 1990’s, some local farmers became alarmed at the speed with which Wheel Cactus was invading their properties and began trying to kill these cactus plants. In 2012, Wheel Cactus (Opuntia robusta) was declared a ‘Weed of National Significance‘ in Australia.