Pest plant, Kahili Ginger Hedychium gardnerianum
I am sure most of you are familiar with Ginger and its impact on native bush. Nonetheless, I have featured ginger this month because it has been a particularly prolific season for the establishment of new seedlings. In many places in your garden and under your trees there is likely to be a carpet of new seedlings. We would like you to join our community drive to weed out this pest plant on your land and nearby bush areas, while they are small and easy to dig/pull out.Control of Ginger:
- Dig out whilst being careful to collect the tubers and roots. Dispose of tubers in a weed bin. Leave the leaves on the ground to rot down.
- Or cut leaves close to the tuber just above the pink collar and paste with cut ‘n’ paste Met Gel. Leave for 6 months before replanting.
When you have a large patch in the open you can spray foliage with 0.5 g/L (about 1ml of granules) metsulfuron-methyl (600g/kg) plus 1ml/L of penetrant. Spraying the foliage, if under treeferns, is not a good idea as it is likely to kill the treeferns and it can even kill mature trees if too much is applied. For this reason, we recommend options 1 or 2 above in most cases.
Under trees
If the ginger you remove is under a canopy of native trees, then you probably don’t need to replant – native seedlings will come up fairly quickly. If you want to replant in a shaded area, Kawakawa (Piper excelsum) is good if it is a dry site and Hangehange (Geniostoma ligustrifolium) is good if it is moist. Parataniwha (Elatostema rugosum) is best in very wet areas.
Steep banks
Ginger is useless at stabilising banks and so you are better off replacing it. However, when removing ginger from a steep bank that does not have other trees established, it is a good idea to do a patch at a time and replant before removing the next patch. There are several options:
- Large tree - Pohutukawa is the best possible bank holding option
- Small trees; Ti kōuka (cabbage tree), or Karo are excellent as they have deep strong roots
- Harakeke (Swamp Flax) (2-3m high) is good for preventing slips but not as good as trees such as above. A smaller (1-2m), but less vigorous, option for banks is the coastal flax (Phormium cookianum).
- Low ground cover; Any of the varieties of prostrate Coprosma or Muehlenbeckia complexa.
Very wet areas exposed to full sun
From small to large: Oi Oi (Apodasmia similis), Pukio (Carex secta), Harakeke (Swamp Flax), Ti Kōuka, Kahikatea.