A Port Hills ranger has cautioned Hurunui to act against the ecological invader Spur Valerian while there is still time.
At a recent meeting in the Hurunui District Library in Amberley, Christchurch City Council Port Hills Ranger Di Carter said there was an opportunity for Hurunui to contain the spread of Spur Valerian (Centranthus ruber). The ecological weed has already invaded Banks Peninsula.
Hurunui District Council’s Water and Land Coordinator Rima Herber called the meeting to look at solutions for Hurunui, bringing together landowners living near two major Spur Valerian infestation areas up the Waipara River and in the Ram Paddock Road area of the Waipara Valley, and stakeholders including Waka Kotahi and QEII National Trust.
Carter said a 10-year spraying programme had been developed for Banks Peninsula in 2013 with funding from Christchurch City Council and Environment Canterbury at a cost of over $60,000 a year after a coastal cliff survey in 2012 had highlighted pockets of Spur Valerian growing along the cliffs.
“At accessible sites it’s been 10 years of two controls a season to get it down to a handful of seedlings per visit – that’s where we are today with those early sites. We spray once a year, with the coastal cliff sites being done by helicopter. By doing this we’re managing to hold it back to Pigeon Bay. I fly with the pilot to minimise non-target damage, and we do the Mount Evans area by foot. With some of the areas around Mount Evans being very vast, it’s easy to miss seedlings, so we also do an hour or two by chopper each year.”
Spur Valerian’s wind-borne seeds are easily dispersed and the plant thrives in rock clefts, dry riverbeds and roadside cuttings, where it is quick to choke native species.
“Spur Valerian migrates from people’s gardens. In a controlled environment, where seed heads are removed directly after flowering and regrowth, and seedlings are destroyed, the plant can be contained. When it escapes into our rural areas, it quickly takes over,” Herber said.
Christchurch City Council Senior Ecologist Nicholas Head told the meeting that the limestone ecosystems throughout the Weka Pass area and the Waipara Gorge, which are under the threat of Spur Valerian infestation, have very high ecological values. “They support some of the rarest and most threatened plants in the country, including the Weka sun hebe (Heliohebe maccaskillii) and Waipara gentian (Gentianella calcis, subsp waipara) that only occur in the Hurunui District.”
“Today, technology offers solutions that will help us as a community to protect our Hurunui environment,” Herber said.
Carter said adapting drones to accommodate oblique angles on cliffs was something Port Hills park rangers were considering. “We’re slowly progressing the technology to make it work.”
“It was wonderful to get a commitment from Waka Kotahi at the meeting to meet me on-site with spraying contractors to work out a plan for the roadside at Weka Pass, where an infestation is threatening the limestone bluffs above the road,” Herber said.
Hurunui stakeholders and landowners will be joining Herber over the next few weeks to go on-site to areas where Spur Valerian is gaining a foothold in the district.