Boneseed – the weed that makes gorse and broom look benign

5 September 2005

Boneseed – a potent introduced plant pest spreading throughout the country – is the target of a joint control action by Christchurch City Council, the Department of Conservation (DOC) and Environment Canterbury (ECan) and the agencies are seeking greater public understanding of the threat posed by this weed.

One project this month in the Christchurch area is an afternoon of work on Cashmere Spur to cut out scattered boneseed plants in Cracroft Reserve. The national Weedbusters organisation will also be taking part.

Volunteers are being sought for this effort – from 1-3.30pm on Saturday (10 September).

While this is a local effort, the topic of boneseed and other invasive species has national significance. This imported plant is a menace but the threat it poses is still not widely understood.

Boneseed, or salt bush, was brought from South African as a garden plant. It is spreading rapidly throughout the country, crowding out other species. It thrives in even poor soil and dry coastal areas, burns easily and comes back even stronger after a fire. Each plant produces up to 50,000 hardy seeds a year. It is spreading alarmingly because birds eat the seeds and deposit them far and wide.

The shrub grows up to 3m, has dull-green toothed leaves covered in a cottony down and its daisy-like flowers come in clusters from late winter until late summer.

The Canterbury Regional Pest Management Strategy objective for boneseed is to  eradicate existing infestations from areas outside the Port Hills and a 20 per cent reduction of infested areas within the Port Hills area over the next 10 years.

“At this stage the aim is to remove scattered boneseed plants and so contain it back to areas of large infestation. In places like Cashmere Spur we can stop it and make a difference,” says Port Hills Ranger Di Carter. “Given sufficient community, volunteer and agency support, this programme may be extended to other areas on the Port Hills.”

● Cracroft Reserve boneseed control effort: Saturday, 10 September 1-3.30pm. Please meet outside the toilet block at the Sign of the Takahe on Hackthorn Road and bring handsaws or loppers if you have them. More info, call 941 8999

● CCC’s weed guide www.ccc.govt.nz/Parks/TheEnvironment/weedguide.asp

● The Regional Pest Management Strategy is on ECan’s site, at www.ecan.govt.nz/Our+Environment/Pests+and+Weeds/

● Weedbusters site is www.weedbusters.org.nz/

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