Council collaborates to save natives from aggressive garden weed

A common garden plant that is devastating rare native species on Banks Peninsula and the Port Hills is threatening Hurunui’s endemic Waipara gentian.

Hurunui District Council Water and Land co-ordinator Rima Herber said Spur Valerian (Centranthus ruber), with its abundant long-blooming, crimson, pink or white flowers, is popular with gardeners because it thrives in difficult spots, such as between pavers and rocks, and can tolerate less than ideal conditions. That resilience, however, says Herber, is what makes it a threat to our rare native species such as the Waipara gentian.

“Spur Valerian is known as a ‘homestead weed’ because it’s easily dispersed from rural gardens, especially if planted near a riverbed, due to its fine, wind-borne seeds.

“We have a five-year opportunity to eradicate it from the Hurunui District and to set up a containment area where there is bad infestation in the QE11 covenant area on Mt Brown before it’s too late and the weed gets out of control,” said Herber.

“It’s a huge pest in other areas and it’s devastating to see it getting a foothold in Hurunui District.”

Herber is organising a series of meetings with stakeholders and organisations including Environment Canterbury, Waka Kotahi and landowners to develop a collaborative plan to rid the containment zone in the Mt Brown area, Weka Pass and the Waipara riverbed of the aggressive interloper.

“If you are in a rural area where the plant has the potential for dispersal, please don’t grow it. To remove it if you already have it, it’s advisable to stump treat it by cutting the plant off at ground level and treating the tips with herbicide,” said Herber.

Herber said a good plant to replace Spur Valerian in gardens was Sedum, ‘autumn joy’, “which has similar hardiness, looks much the same and isn’t invasive. It’s also a great plant for butterfly food in early autumn”.

Spur Valerian flowers from October to February.