14 May 2007 2:41 PM

I've just spent the better part of a morning removing an infestation of balloon vine (Cardiospermum grandiflorum) from my boundary fence.  This menace is a real problem here, particularly along the banks of the Nepean River where it covers hundreds of hectares, swamping everything in its path and getting up into the crowns of the river oaks and eucalypts. Apparently it originates from tropical America, the West Indies and Africa.

As I was removing yet another 5 metre length of vine from a turpentine tree, I started to wonder how this pest ever got to Australia in the first place.

Now, my understanding is that there are at least three possible mechanisms through which exotic weeds develop:

• Agricultural escapees – eg. Exotic grasses used for pasture improvement that refuse to remain confined to the pasture
• Garden escapees of ornamental plants
• Hitch-hikers – eg. Seeds brought in inadvertently on ships or aircraft.

So where does balloon vine fit?

As far as I know it has no agricultural application and, if it's a garden escapee, then I'm at a loss to understand its attractions (its white flowers are not particularly conspicuous, its fruits are drab and its foliage is nothing special). Why would anyone want to grow it willingly?

Perhaps it's a hitch hiker.

If so, can we send it back?......

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