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Coastal weed discovered in Whangamata

The plant pest boneseed, or salt bush, has been discovered in Whangamata, and Environment Waikato is anxious to get rid of it.

Boneseed, also known as salt bush or bitou bush, is a threat to low coastal vegetation, where it can rapidly take over and replace native plants, including pohutukawa. It is a fast growing shrub that can produce up to 50,000 seeds a year. Environment Waikato regards it as a ‘containment’ pest, requiring removal of all plants.

Biosecurity contractor Pest Plants Jeff Jeffrey said plants were found on two properties in the Whangamata township during routine inspections.

“This is the first time that this plant has been found in this area. If this plant is not controlled now there is a potential for an invasion along the eastern seaboard, which would be environmentally disastrous.”

He said the plant’s thick growth could restrict people’s access to beaches, and it could be difficult to control because of the large numbers of seeds it produced. Seeds could also remain dormant in the soil for up to 10 years. Birds and possums ate the fleshy fruit and spread undigested seeds into neighbouring shrub lands and coastal forests.

Seed germination was stimulated by fire, and it grew best in dry sunny conditions in coastal areas, cliffs, sand dunes and wasteland. The bushy shrub grows up to three metres tall, with leathery, paddle-shaped leaves, with toothed edges and a powdery surface. It has yellow daisy-like flowers from September to February, and clusters of small fruit that turn from green to black when mature.

The South African native was first brought to New Zealand as an ornamental plant. Infestations have previously been found around Waihi, Raglan and the Coromandel Peninsula. Boneseed is also banned from sale, propagation, distribution or commercial display.

Boneseed can be controlled by pulling out small plants, composting those without seeds and taking others to refuse transfer stations. Larger plants usually needed to be treated with herbicide, as they would re-grow. Environment Waikato has free fact sheets and can identify suspect plants for landowners.

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