Beware of the Aliens in the Cactus

Beware the Wheel Cactus

Cactus fruit

Fox shit! How interesting is that? Why am I wandering around Mt Tarrangower and examining the faeces of Vulpes vulpes, the Red Fox? Well, it’s all part of understanding the distribution of the Wheel Cactus (Opuntia robusta), a difficult to eradicate, introduced species threatening our bushland and farms. So yes – we must beware of the aliens.

Mid-winter and there is still fruit on the Wheel Cactus. This impressive foreigner with its obvious round grey-green wheels, its bright yellow flowers and then the dark red fruit, is now firmly established on the mountain and many properties close by. Classified as a noxious weed, the cactus is proving difficult to control and for the most part this is due to a lack of manpower coupled with some landholder inertia.

Drive along any of the roads to the north west and west of Mt Tarrangower and you will see platoons of baby green discs reminiscent of cute little aliens from an episode of Doctor Who. In no time at all, each will have added another disc to itself, and then another and another and, while that is happening, each disc is quietly growing bigger. But how did this all happen?

So how do we get rid of Opuntia robusta? The recommended approach is to remove it while it is very young. The baby cactus can be pulled from the mostly granite soils quite easily. Importantly, the plants should be taken away to be destroyed, or put somewhere up off the ground. Like the little aliens they are, they will just re-establish themselves if left lying around. Bigger cactus require more desperate action and that involves injecting a chemical into each and every wheel on the plant. Miss one and it will topple from the injected wheels, grow roots, and become a new plant.

Wheel Cactus fruit

We have no firm evidence about when the Wheel Cactus first arrived. There are many stories, from the succulent-collecting elderly lady living on Pigeon Hill, to the nice Italian market-gardening family who lived along Parkins’ Reef Road. (This family was also said to have grown at least one Stone Pine tree for pine nuts.) These stories date from around the 1930’s and 40’s but the plant may have arrived much earlier. Think how useful such a quick growing decorative and drought tolerant fruit-bearing plant would be in times when fresh fruit was only seasonally available and scarce, and when people were just settling around Maldon, building houses, cow, pig and poultry sheds, and establishing vegetable gardens and orchards.


Our region does have its dedicated cactus warriors. Usually keen landowners, they have spent a lot of time doing practical research to better understand the problem.
We know that the cactus fruit is eaten by the common crow – the Australian Raven (Corvus coronoides), and the fox. Local research has shown that a crow can travel four kilometres before defecating, so that makes it the number one friend of Opuntia robusta. Those platoons of perky baby cactus scattered so evenly beneath a tree have been sown by a crow from high up in the tree.

Occasionally – and usually most often in the forest – you will see a big clump of older cactus with the plants pressed close together. Or you might see a tight circle of baby cactus. These will most likely have originated from the droppings of the Red Fox. Reynard eats cactus fruit and you will often find evidence of this when you check his scats. Bright orange or red and quite soft, almost runny, they are full of browny-yellow cactus seeds.
So why and how should we help combat the Wheel Cactus?

The problems with cactus

Watching a black wallaby desparately trying to navigate its escape up an incline infested with cactus, quickly tells us why we should fight the pest in our forested areas. Our native animals’ living space is under attack. The cactus also takes land away from native trees and shrubs and ground cover plants.

On farm land and roadsides, if not controlled, the cactus will fruit and many of the seeds will be taken to forested areas by birds and foxes.

There are Landcare groups all around Maldon, each with its own active regional eradication program; and they welcome new members. You don’t need to be a rural property owner to join. Maldon, Baringhup and Nuggety have their groups and in association with Parks Victoria, have monthly cactus eradication days. They provide the back-packs and associated equipment. You just need to dress as though you were going bush-walking, oh yes, and take some work gloves. A sausage sizzle rounds off the day.

Well, I’m still here with the problem. Can’t leave this fox shit sitting here. Its full of aliens you know. I had better get a doggy bag. Beware the aliens!