Wild ginger

Wild ginger.

Common names:
Wild ginger
Yellow ginger

Scientific name:
Hedychium gardnerianum
Hedychium flavescens

Regional classification:
Only boundary control adjacent to roadside and could be enforced if roading authority has an active control programme in place

National classification:
National Pest Plant Accord – banned from being sold, propagated or distributed

Description

The name ‘wild ginger’ applies to two species:

kahili ginger - Hedychium gardnerianum
yellow ginger - Hedychium flavescens

Wild ginger tuber roots.

Kahili ginger is the most common and most invasive of the two. Yellow ginger is less common.

Both form dense colonies in native bush, on roadsides and riverbanks, smothering and eventually replacing all other species.

Distantly related to culinary ginger, wild ginger has a faint ginger smell and taste and has been used as a ginger substitute during wartime rationing. Highly palatable to livestock, both species tend to invade all areas where stock are excluded.

Both species are non-woody perennials, growing from thick-branching rhizomes (swollen underground stems). These taro-like rhizomes have 4cm to 10cm segments, each producing vertical stems annually.

Rhizomes form dense beds up to one metre deep excluding all other species.

Flowers:

attractive flower heads shaped like a Chinese lantern
appear between January and March

Kahili ginger flower head:

25-45cm long
flowers are scented
lemon yellow with conspicuous stamens

After the flowers fall, prominent fruiting spikes remain, producing 1.5 to 2cm long fleshy orange fruits in winter, each fruit containing small shiny red seeds. The fruits are eaten by birds and in this way the seeds are spread. Yellow ginger does not fruit.

Why is it a problem?

All fragments can resprout, no matter how small. Kahili ginger seeds can be carried long distances by birds, frequently into bush, to create many new infestation sites.

Wild ginger out-competes other species for light, space and moisture.

Treated tubers can be covered with cut foliage. Wild ginger is ecologically very versatile, thriving in bright light or dense shade, in good or poor drainage and a wide range of soil types. It can even sprout in tree forks like an epiphyte.

Wild ginger out-competes other species for light, space, nutrients and moisture.

Although rhizomes form dense mats, roots are shallow and maintain poor purchase on soil, which means the heavy mats can become an erosion hazard in bush when parts give way. Entire hillsides of ginger have been known to slip away at once.

In time, entire forest areas are completely taken over by ginger.

Your responsibility

The wild ginger species are pest plants in Northland and cannot legally be propagated, sold or distributed. In addition. we may require control measures to be taken.

The long-term goal is to totally eradicate these species from Northland.

Recommended control methods

Site management:

Maintain rolling front, eradication can be easily achieved.
Don’t replant sprayed sites for six months.

Recommended approaches:

Slash stems & dig out all rhizomes.
Young seedlings can be hand pulled, taking care to remove strings of rhizomes.
Cut above pink “collar” at base & stump paint (0.5g metsulfuron/1L or Vigilant gel).
Spray dense patches away from roots of vulnerable species, spring - late autumn (5g metsulfuron + 10ml penetrant/10L).

Disposal:

Remove seedheads and take to landfill.
Stems & leaves can be mulched but any fragments of rhizomes will regrow.
Don’t compost, mulch or hang rhizomes in trees, as they survive indefinitely; bury them at landfill or dry & burn.

Caution: When using any herbicide PLEASE READ THE LABEL THOROUGHLY to ensure that all instructions and safety requirements are followed.

More information

For further information or control advice please contact one of our Biosecurity Officers at the Northland Regional Council on 0800 002 004:

Whangarei: Ken Massey
Dargaville: Peter Joynt
Kaitaia: Doug Foster

Environment