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 originated in Mexico.  There are reports of earlier sightings in our local district, however these may have resulted from confusing the Wheel Cactus plant with other common cacti, such as Prickly Pear (Opuntia stricta) and Riverina Pear (Opuntia elata).

Prickly Pear and Riverina Pear (close cousins to Wheel Cactus) were planted in many house gardens since the Gold Rush era of the 1850’s, but they did not tend to spread beyond their original locations. Large ‘prickly pear’ plants can be found at many sites where a homestead and garden once existed. Although some are potentially problematic in spots, none have 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 natural assistant in spreading the plant 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 large 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 a serious problem in 1963. Maldon Times May 13 1963 Maldon Times May 13 1963

A photograph in a 1976 publication (Noxious Weeds of Victoria by W.T. Parsons) looks remarkably like the rocky granite hills around Mount Tarrangower.

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.