By Sara Brill, Biosecurity Specialist – Pest Plant Partnerships at Northland Regional Council

Most of the time, autumnal shades of yellow, orange and red are a sight for sore eyes. However not all plants with these golden hues are something to celebrate, including Kahili ginger (Zingiberaceae – Hedychium gardnerianum).

Kahili ginger is native to the Himalayas in India, Nepal and Bhutan and, as the name would suggest, it belongs to the ginger family. With its striking appearance and fragrant deep golden flowers, Kahili ginger is a popular ornamental plant in many parts of the world. In contrast, several countries including Aotearoa New Zealand consider it a pest, and it has been included in the ‘100 of the World’s Worst Invasive Alien Species’ list by the International Union for Conservation of Nature.

This pest plant can be easily identified thanks to its distinctive yellow flowers, long red stamens, and fleshy orange fruits. Kahili ginger usually grows 1-2 metres tall but can reach up to 2.5 metres.

Kahili ginger is a ‘forest invader’ that thrives in the damp fertile soil of forests and riverbanks. It is also commonly found alongside roads and in gullies thanks to birds spreading seeds across long distances. It is extremely shade tolerant, hardy, and has a long-lived creeping root system that can form stacks of roots up to one metre high. It forms dense clumps, smothering young plants and preventing native seedlings from growing.

How to control Kahili ginger

Physical control:

• Hand-pull small seedlings, crush or dispose of carefully.
• Dig out small clumps, ensuring all the root system is removed and disposed of safely.  Rhizomes can be crushed and dried then burned. Larger clumps should be sprayed with herbicide.
• When removing Kahili ginger, remove flower heads as a stopgap before spraying or removing the whole plant. This won’t kill the plant but will stop it from seeding that year. Burn or dispose of the seed heads in landfill.

Herbicide control:

• Cut stems and paint stumps with 1g metsulfuron-methyl (600g/kg e.g. Escort®) per 1L water.
• Spray 5g metsulfuron-methyl + 10ml penetrant (e.g. organosilicone) per 10 litres water.

When using herbicide please read the label thoroughly and ensure all instructions and safety requirements are followed.

For more information on Kahili ginger:
W: www.nrc.govt.nz/pestcontrolhub | P:  0800 002 004