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Pests Pest outbreaks Invasive pests Is vetiver invasive? Samoa

Is vetiver invasive?

November 2008. A message from a member in Samoa about the changing status of vetiver grass.

The literature claims that the cultivated varieties of vetiver will continue growing in the same spot for 100 years without spreading and observations in Fiji seemed to support this claim as vetiver has been there for at least 50 years or so without becoming invasive. However, Warea mentions (below, para 3) that in Fiji, vetiver is naturalising and has become invasive. Is vetiver undergoing a behavioural change – perhaps induced by climate change or some other factor? It seems that a similar phenomenon happened with African tulip which was a “nice, friendly plant” in Fiji (and Samoa) for quite some time before becoming invasive. May I ask Warea to kindly explain further the severity of vetiver invasiveness
that he observed.

The submission above followed on from a much earlier one sent to PestNet 26 February 2004.

Vertiver (Vertiveria zizanioides) has been used for thousands of years in India for stabilising bunds in irrigated rice fields. Apart from erosion control vertiver can have various uses including use of leaves for thatch, mulch, making natural hedges and marking land boundries, and vertiver oil production. In the highlands of Papua New Guinea it is now being promoted for reducing erosion in very steep cultivated areas such as Simbu Province where 70% of the province lies between 1000-2600 metres above sea level and 40% of the land has slopes greater than 20 degrees. Vetiver’s erect leaves make good thatch and is also seen as an alternative to Kunai grass (Imperata cylindrica) which has been replaced by the invasive, less useful grasses Pennisetum purpureum (Elephant grass) and Melinis minutiflora (May grass).

The vertiver stands Iseen in Fiji appear to be naturalising and invasive.