Clematis vitalba (old man's beard) is an invasive pest. Photo / Getty Images
Clematis vitalba (old man's beard) is an invasive pest. Photo / Getty Images
Many plants were introduced to New Zealand for their beautiful flowers, leaves or seeds. Unfortunately many became weeds and Whanganui has lots. They are not just unsightly; some of them can topple large trees.
Most of our gullies and parks have severe weed infestations. Community groups in some cities have adopted gullies and transformed them by removing weeds and planting natives or non-weedy plants. Whanganui needs this approach.
Dealing to weeds is very satisfying, especially pulling and cutting as you see immediate results, but it can be overwhelming if it is persistent or there is too much.
In this, my first piece on weeds, I want to focus on the climbing ones.
Here is my top 10 of worst climbers: ivy, old man's beard, climbing dock, convolvulus, banana passionfruit, Japanese honeysuckle, jasmine, Madeira/mignonette vine, blue morning glory and climbing asparagus.
The good thing about climbers is that they mostly don't flower until they climb. You'll see ivy (Hedera helix) scrambling over the ground without flowering, but when they manage to climb up flowers appear and hard purplish seeds will produce new plants.
Small infestations can be cleared by digging or pulling. This is harder if underground stems are near trees or man-made structures.
Weeds that have climbed high can be cut into "curtains", or, as I think of it, a "fringe". Cut well above the ground and let the parts that are up in the tree die and dry where it is. This usually kills parts above the cut and the host tree will release itself from their grip.
However, some climbers will continue growing if there is enough moisture on the host tree. If host trees are large they can have pockets of soil where the branches fork. I have dealt with ivy that was thigh-thickness on a very large plane tree with lovely fertile pockets of soil up high. It took a few years and a very dry summer to die.
The parts on the ground are the hard part. Now is not a great time for using herbicide.
Springtime is best. If you've cut your climbers into "curtains" or "fringes" leave the stems at the bottom until springtime before you re-cut them low and gel or spray the cut.
If the growth is extensive this treatment will not kill the whole vine and blanket spraying may be needed or diligently cutting along the stems. Be careful about leaving pieces of stem lying around: many species will re-sprout.
Convolvulus can smother native trees and shrubs. Photo / Getty Images
Some vines sprout from the nodes along the stem if they touch the ground, especially ivy, old man's beard (Clematis vitalba) and jasmine (Jasminum polyanthum).
Most plants will die once you cut the roots and remove the stem/upper part, but not all underground parts are roots. Some, like convolvulus, have long underground runners making it very hard to control.
Climbing dock (Rumex sagittatus) and climbing asparagus (Asparagus scandens) have tubers that mean cutting the root is not enough. The former is currently in "seed", its most attractive (pink) but also most damaging phase as it releases the seeds into the wind. Its large kumara-like tubers on chains of root are easily spread and re-sprout. This weed wasn't around much when I arrived in Whanganui in 2012, but now it's everywhere.
Likewise, blue morning glory (Ipomoea indica); it has become rampant only in the last few years. Its flowers are absolutely stunning, but it needs to be controlled as it will kill large trees.
Much more can be said about this, but that is for another time. For more information check: www.weedbusters.org.nz
Contact your local council (WDC or HRC) if you are keen to set up a group. They might be able to help and so am I.
