Think of a privet hedge and you think of respect-ability. Its neat, glossy leaves are to the British suburban garden what net curtains are to the British suburban house. Orderly and clipped, the privet hedge (the very name has overtones of privacy) is the tame antithesis of the tangled hedgerow. It comes as a surprise, therefore, to learn that in some parts of the world, the 40 or so species of shrubs and small trees belonging to the genus Ligustrum (which is, in turn, part of the olive family) have a rather less than genteel reputation.

In Australia, where the British introduced it as an ornamental plant in the early days of the colony, it seems to have found an ideal habitat, to the extent that it has now become a serious environmental threat in the eastern states. In a report entitled Plant Invasions of Australian Ecosystems, privet is described as “a major invader of sub-tropical rainforest”. Because its young seedlings survive in deep shade, are abundant and capable of fast growth, they rapidly replace native species.

The seeds are easily spread by birds, so privet has been found choking drains and gullies. And as if that’s not enough, the plant is poisonous to humans. They may not have told you this when you were knee-high to a hedge (the words “dangerous” and “privet” somehow don’t go together), but the common or garden Ligustrum vulgare contains a glycoside which can kill horses, sheep and cattle and which has been known to poison children.

The symptoms of privet poisoning are gastro-enteritis and vomiting, and it’s those prim green leaves that are responsible, together with the purple or black berries that resemble tiny olives. In addition, the Australian health authorities believe privet flowers can cause asthma attacks, and in some states the plants have been declared a “noxious weed”.

Are we still talking about the stuff of which Acacia Avenues are made? Afraid so.