If you have recently travelled along SH1 between Wellington and Paekakariki you may have noticed that some of the roadside cuttings and banks are tinged with pink. The culprit is the daisy pink ragwort (Senecio glastifolius).
Pink ragwort is native to a small area of coastline in South Africa and was first recorded in New Zealand in Gisborne in 1963 and in the Wellington region soon after. How it reached our shores is unclear as there are no records of plant nurseries growing or selling it. Pink ragwort subsequently spread to other areas of New Zealand, with some movement probably occurring through its deliberate planting as an ornamental garden plant. It is primarily a weed of open areas including disturbed ground, agricultural land and coastal areas.
A recent thesis by Victoria University of Wellington student Josef Beautrais examined the spread of this weed. Using species distribution modelling, Josef found that pink ragwort is occupying a different niche in New Zealand to what it occupies in its native South Africa. Of more concern, he found that there are large areas, including the northern third of the North Island, that offer suitable habitat for pink ragwort but that have not yet been invaded by this species.
Should we be worried about pink ragwort and its growing distribution? In many disturbed sites, which are already full of weeds, it isn’t too much of a concern. However, it is a serious threat to coastal sites where it can crowd out low-growing endangered native species such as Pimelea actea and Sebaea ovata. It is banned from being sold and propagated in Taranaki and Northland and is being controlled at some sites near Whanganui.