Weed Watch – Gorse

 

Gorse in flower. Photo courtesy Frances Schmechel, Environment Canterbury.

Gorse in flower. Photo courtesy Frances Schmechel, Environment Canterbury.

Gorse seeds first arrived in New Zealand in the early 1800s in response to the English settlers’ desire for hedging. A natural lack of control agents in New Zealand, combined with high seed production, unpalatability to stock and invasive, colonising growth habitats, have allowed gorse to become the widespread problem it is today.

Gorse (Ulex europaeus), is now a major invasive plant species in New Zealand and millions of dollars are spent on its control. As one of the country’s most widely recognised agricultural weeds, it covers around 700,000 hectares – a total of 5% of New Zealand land area, excluding existing indigenous forest and vegetated alpine and sub-alpine areas.

Gorse seed can lie dormant in the ground for up to 50 years and unfortunately, when adult gorse plants are removed, ideal conditions are created for that dormant seed to germinate.

Biological control of gorse has been investigated since the 1920s but large scale control of this pest plant has not been achieved. One method that does appear to have some success, is the germination of native tree and plant seedlings that can grow up through leggy, adult gorse plants, eventually cutting out its light and replacing it. This technique has been used successfully at Hinewai Reserve on Banks Peninsula.