Dismantling feral ecosystems

Basalt escarpent, overrun with serrated tussock

I’ve been privileged to work for a few weeks on a basalt escarpment in Melbourne’s western suburbs. The area is spectacular; I love the views and geology and flora of the escarpments. Even this one, which is seriously infested with invasive exotic species.

The section I’m working on is overrun with serrated tussock (Nasella trichotoma), a South American native that causes big problems in agriculture and native grasslands. It’s an attractive species, but tends to smother everything around it – and its seeding panicles (seedheads) break off and blow in the wind, spreading it far and wide. Native animals, stock, and even rabbits barely touch it, preferring to eat almost anything else including all the native species. So it has a great competitive advantage, and easily takes over (especially under heavy grazing). It sets thousands of seed per plant, building up a huge reservoir in the soil seed bank. Continue reading

Advertisements

Burrs: The trials and Tribulus

Tribulus terrestris, three-corner jack

Tribulus terrestris is a terror of a burr. Large, strong spines that can stick into tyres, shoes and of course feet, spreading in harsh dry environments where other plants are struggling, resistant to council spraying efforts.

Locals here usually call it three-corner jack (a reference to the shape of the burrs). Caltrop is another name, taken from a weapon of ancient warfare, a steel spike that was left on the ground to pierce the feet of enemies like a precursor to landmines.

It goes by various common names. One of these, bindi-eye, is more familiar to me as the common name of Soliva sessilis, a small lawn daisy with a nasty burr that my bare feet met as a kid in Queensland.

The weed is well adapted to sandy dry soils and dry weather. It competes for moisture well with other plants, and can survive drought. An annual, it spreads rapidly along the ground in all directions, setting thousands of seeds, which can persist for several years in the soil before germinating. Continue reading

Native plants vs Agapanthus

Agapanthus. Not a native.

A while back I was in the largest chain of hardware/garden/etc stores’ local (Melton) outlet and saw a big selection of Agapanthus lilies for sale in the “Native Plants” section.

According to the informative article here, the “Black Pantha” variety produces few if any viable seed, which is a bonus. I don’t know about the other varieties that were on offer, though. The plant can become a weed in areas with a suitable climate. It’s native to South Africa, like a lot of our worst ecological weeds.

This is clearly not a native! I could leave it at that as a comment on the uselessness of big chain stores, but let’s explore this a bit more. Continue reading

Introduced weeds of the Werribee River

Here’s a list I prepared for a talk on weeds at a tree planting day by the river. These are all species I have observed along the river in Bacchus Marsh. 

Bob Reid said he might see if he can make a list of native species from the river as long as this. It’s a very disturbed environment with a lot of invasive weeds!

Not all these are particularly problematic, many just colonising disturbed ground in the absence of natives. Bold indicates those that seem to be the main problem species.

There are undoubtedly more, especially grasses, rushes/sedges and aquatics which I am not confident to positively identify.

You can use the web links at the bottom of this post to look up colour photos of them and further information. Continue reading