What is it?
Ivy (Hedera helix) is a plant that is widespread and well recognised throughout New Zealand, often being used to cover buildings, fences, walls and banksides in our cities and towns.
As a result of its popularity, there are many cultivars of ivy, with a range of different leaf shapes and colours.
In all forms, however, it is a perennial climber with stout woody stems that can cling to almost any surface through a mass of small aerial rootlets. The leaves are usually dark green, but may be mottled with patches of white or yellow in some cultivars. The shape of leaves also varies across cultivars. Dark purple to black berries are also noticeable during winter.
Why is it a problem?
Ivy is one of the most effective climbing plants around and, while this makes the plant popular in urban environments, it also means it can be a pest in the wrong place. When spreading unchecked, it can smother and kill all plants in its path, from the forest floor to the canopy. It can even develop enough weight to bring down branches or even whole trees.
Unfortunately, it is also able to tolerate a wide range of conditions and soil types, meaning it can spread just about anywhere in New Zealand, from forest and open country to coastlines and tussockland. In addition, birds readily spread the seed and the plant is very hard to successfully kill and dispose of.
Methods of control
Manual control: Small sites can be controlled by removing all stems in contact with the ground, and digging up the roots.
Chemical control: When ivy has climbed into the forest canopy, the cut stump method provides an effective form of control. Cut vines to ground level at any time of the year, and then apply herbicide to the cut stump at the rate recommended by the manufacturer. Suitable herbicides include Vigilant, Grazon, Escort and glyphosate-based herbicides, such as Roundup and Touchdown.
Care should be taken to cut the vine horizontally, so that the herbicide will stay on the cut area and be absorbed. Many people are sensitive to ivy, and get skin irritations when handling it. Wear long trousers, long sleeves and gloves when handling ivy, and avoid getting sap on the skin. Herbicide uptake will begin to decrease as soon as 30 seconds after cutting, so apply immediately to ensure this method is effective. There are several convenient ways the application can be made, with a paintbrush, eyedropper or a small squeeze bottle.
Because of the way ivy clings to any host tree, it is best to leave any remaining stems to die. Pulling them out has the potential to severely damage the host tree.The cut stump method can also be used for ground infestations of ivy, in which case it is safe to remove the cut stems and smaller roots beforehand.
Spraying is also possible, although this requires the use of more herbicide and is liable to affect non-target species as well. Preferred herbicides include Grazon and Escort, at the rates recommended by the manufacturer. Spraying should only be undertaken during summer, and will require the use of a suitable penetrant, such as Pulse or Boost. Take care to spray only in still conditions to avoid wind drift to non-target plants, and donÃt spray when rain is expected.
During spraying, non-target plants can be shielded with cardboard, plastic sheets or a large plastic container. The use of a marker dye helps to avoid double spraying and wastage, and a foaming agent can be added to the spray to help prevent spray drift. As with all spraying, you should read the instructions on the manufacturerÃs label closely and always wear protective clothing.
Ivy is hard to kill so, whichever method is used, it will be necessary to revisit the site to ensure there is no resprouting from stumps or that remaining stems have not layered into the soil.
Disposal: Ivy needs careful disposal. Any stems that have been removed should be buried deep into the soil, burnt, or placed in a sealed black plastic bag and left to rot in the sun.