Pest plant: wild ginger
Kahili ginger is the most common pest of the two in our region. Photo: supplied
Wild ginger has the potential to completely dominate the understory of native forest as has occurred in areas north of Auckland.
There are two species of wild ginger; Kahili ginger (Hedychium gardnerianum) and yellow ginger (Hedychium flavescens).
Kahili ginger is the most common pest of the two in our region. I have only come across one yellow ginger plant at Tukurua. Kahili ginger is originally from India and Nepal, and was grown for its strong scented bright flowers. Incidentally the rhizomes are not edible and it is the ginger plant (Zingiber officinal) that is grown and imported from Asia, for edible root ginger.
Kahili ginger grows prolifically in dense clumps with; persistent rhizomes, broad shiny leaves up to two metres high and spreads under forest canopies. Flowering begins in late summer to early autumn, eventually producing bright red seeds, which birds eat and distribute far and wide.
It has been previously planted throughout Golden Bay by gardeners. As a result of its prolific growth taking over their gardens, a few have removed the rhizomes and dumped them on rural roadsides, where it has started remote ginger infestations. The Collingwood and Parapara beach settlements are two examples where Kahili ginger infestations were started by birds spreading seed from garden plantings into a substantial infestation of both young plants to dense clumps of ginger. Wild ginger has a national MAF Biosecurity ban on its sale and propagation.
The Tasman-Nelson Regional Pest Management Strategy requires occupiers in the Golden Bay district to Kaiteriteri, to control all adult and juvenile ginger plants on land they occupy.
Small seedlings can be grubbed out. Dispose of the rhizomes in your domestic rubbish or arrange disposal at your local rubbish transfer site. The rhizomes will sprout readily if dumped on soil and will even continue to grow if composted.
The very best control method is to carefully spray the leaves, stalks and rhizomes with metsulfuron plus penetrant. My experience shows that if you are thorough in wetting all the ginger plant with metsulfuron, it will gradually yellow off and succumb completely.
For very small plants you can cut off the leaf stalks close to the ground and “stump treat” the stalk stumps with Vigilant Gel.
If you would like further information on control methods and herbicide types, please phone your biosecurity officer through the TDC office on 525 0020.
Submitted Ken Wright, TDC biosecurity officer
