Join the battle against invasive ivy
Save the Puahanui forest, visit Gwavas garden homestead
Are you moderately fit, able to climb over fences and get down to ground level, and have an overwhelming urge to pull out ivy? If so, the Gwavas Charitable Trust needs you.
After a break of one year due to Covid, the annual Gwavas Charitable Trust Ivy Pulling Day at Puahanui Bush is on Sunday, May 29, and project manager Kay Griffiths says the trust would love to have your help for the day.
For almost two decades, the landowners have been working to eradicate weeds from the 130ha private forest which is home to trees such as rimu, totara and matai.
“For decades this magnificent podocarp forest — the largest dryland podocarp remnant in the country — has been strangled by common ivy, with the weed spreading to two thirds of the forest,” says Kay.
It is the largest documented invasion of English ivy (Hedera helix) into a native habitat in New Zealand.
The ivy had become established over the last 100 years.
“While ivy is lovely in an English garden and great ground cover, once it is mature it changes to its adult form, seeds and spreads,” says Kay.
“Ivy roots can send out a shoot at every node. It can travel 20 metres and it can break off and start a new plant. Some of the plants in Puahanui Bush would have been 50-80 years old, it was knee-deep over half of the 130 hectares. As the ivy got to the trees it climbed — some of the ivy trunks were as thick as a person’s leg and when there are seven or eight like that climbing up one tree, the huge weight has a devastating effect on the canopy trees.
“The ivy covers growing trees and stops them growing. It impedes seedlings, takes over and shades them out and the environment starts to lose its diversity.”
Control began in 1999 with cutting of the adult vines and application of herbicide.
“Then we discovered that using a weedeater to bruise and defoliate the plants before using herbicide gave a good result. We also trialled grazing sheep on the ivy. Literature said it was not palatable but we found the sheep liked it and did well on it.
“In some places there were at least seven native species that just stopped growing. Today, while there are still small bits of ivy in the bush, there is nowhere near as much as there used to be, but it has taken a long time to get the levels down.”
Kay says the trust is in the maintenance phase of the weed control programme, which will take a long time because it’s not known how long the seeds are viable for.
What makes this bushland even more unusual is that it is privately owned, located behind the Gwavas
Garden property in Tikokino. It has been kept intact by the same family which has owned the property for more than a century.
The bush supports regionally rare long-tailed bats, bush falcon, large numbers of tui and kereru, forest gecko, and a range of unusual invertebrates.
“It is amazing that this forest exists and that it wasn’t levelled to make way for more farmland.”
There will also be the opportunity on the day to look around the Gwavas garden and the homestead, built in 1890 and now a Category One listing with the Historic Places Trust.