Time to stop pest plants jumping the garden fence

Japanese honeysuckle being removed. Credit: Te Ara

Many of our most noxious weeds including old man’s beard, Japanese honeysuckle, English ivy, wild ginger, and buddleia have jumped the garden fence to now threaten our native biodiversity.

A new report is calling for a coordinated approach to nipping that in the bud.

Philip Hulme, Professor of Plant Biosecurity at the Bio-Protection Research Centre, Lincoln University is the lead author of the report compiled by an international team of scientists.

Professor Hulme said a more rigorous approach to assessing risks from over 30,000 plant species, cultivars and varieties on sale across New Zealand, is needed. Action has to be taken before species escape from gardens, not after.

He said balancing the needs of the garden industry against the threat of plants spreading from gardens and impacting on native wildlife is a major challenge.

“We examined the multitude of different approaches in managing garden escapes around the world and found that in most countries policies for managing pest plants were fragmented and uncoordinated.”

The report proposes countries adopt a seamless approach to managing pest plants from the national border to the garden bed, which involves the government, industry and the public having sufficient knowledge to make informed decisions regarding what to import, retail and purchase.

At the New Zealand border it is the industry rather than the government that bears the cost of assessing the risks posed by any new plant species they wish to import.

Post-border, the industry works closely with government and scientists through the National Plant Pest Accord (NPPA), to identify and remove known pest plants from sale.

Professor Hulme pointed out some weaknesses in this approach.

“The perceived high cost of importing new plant species encourages illegal imports and although the NPPA is a great model of collaborative working, most retail sales bans only occur once the species has already jumped the garden fence.”

“We should also be investing more in public awareness of this issue, perhaps by labelling species in relation to the risks they pose or giving much greater profile to native alternatives at the point of sale,” recommended Professor Hulme.

Hulme PE, Brundu G, Carboni M, et al. Integrating invasive species policies across ornamental horticulture supply chains to prevent plant invasions. J Appl Ecol. 2017;00:1–7.