A rare plant that could be a weed

Trianthema triquetra is a prostrate, succulent herb, with small fleshy leaves, tiny white flowers and globular red fruits.   It is known from a single location in Victoria, on a disturbed roadside, a few hundred metres from the Murray River.  A single sweep of a grader or a simple road upgrade could wipe out the whole population.  It is classified as endangered in Victoria.

The first and only time that Trianthema has been recorded for Victoria was in early 2007 - it was found by a local botanist while travelling to NSW.  As it is an Australian native species and it has not been deliberately planted, its occurrence in Victoria is considered to be natural and hence the endangered classification.  If it were not natural then it would be regarded as a weed and there would presumably be plans prepared for its eradication.  When observed in the field, Trianthema looks like a weed.  It is often found on roadsides, sometimes growing directly on gravely substrates before other species have colonised.  It is very similar in habit to Portulaca olearacea (Common Purslane) which is undoubtedly weedy in its behaviour (it is common along urban paths) but is regarded by some botanists as native and by others as a weed.

A little south of the Murray River, in far north-western Victoria, there is another native plant that is classified as endangered in Victoria and it nearly always grows on or near disturbed river banks.  The species is Swainsona greyana (Hairy Darling-pea) and like many other peas it is an opportunist, it looks and behaves like a more robust form of the non-native vetch (Vicia sativa) which is unambiguously a weed in Victoria.  Nevertheless it is accepted that this attractive plant it is native to Victoria despite the fact that there was no record of the species until 1962.

There is greater ambiguity associated with the endangered classification of the shrub Gaultheria hispida which has been recorded from a single location in the Otway Ranges about 100 km south-west of Melbourne.  The plants were first recorded in 1994 on a disturbed roadside and many Victorian botanists regard the species as an introduction rather than natural.  Similar questions could be raised about the naturalness of the succulent herb Hemichroa diandra (classified as endangered) which is widespread in NSW but known from a small area at the northern end of a saline lake in the Mallee, very near an old salt-mining plant.  None of the Victorian specimens produce seed.

The grass Panicum obseptum is also a species upon which botanists cannot agree.  In 1991 the Department of Natural Resorces and Environment (NRE) listed it as a native species which was classified as rare in Victoria.  In 1994 the Flora of Victoria determined that while Panicum was native to NSW it was not a Victorian native.  The current DSE classification for Panicum obseptum is that it is native to Victoria but it is no longer rare and it is weedy in some parts of the state.  In a slight variation to this theme the wetland herb Sparganium erectum was also once listed as rare by DSE but was later determination by the Victorian Herbarium to be non-native.  In a reverse of this situation the slender herb Lepidium hyssopifolium was for many years regarded as a widespread roadside weed in Victoria.  Research into the lepidiums a few years ago, however, changed all that and now Lepidium hyssopifolium is considered to be a  native species which has been classified as endangered in Victoria and Australia..

One of the more convoluted examples of mis-determination involves the grass Eragrostis trachycarpa.  It was once classified as vulnerable in Victoria and  a few years ago it was successfully nominated for listing under the Flora and Fauna Guarantee Act (FFG). Shortly after the nomination, however, the same botanist who nominated it for listing submitted a nomination for delisting on the basis that the plant was more widespread than once thought and was, in fact, growing like a weed in - amongst other places - his chicken run. The delisting nomination was successful (the only one on record for the FFG) and the species conservation status has been reduced to rare by DSE botanists.