What is ivy?
Ivy is a woody stemmed, self-clinging climber that can grow quickly into the canopy of a tree. Where it grows as a trailing, ground-cover plant it roots in at many points and its stems extend over a wide area.
The botanical name for ivy referred to on this page is Hedera and it includes the native climber English ivy (Hedera helix). These are unrelated to the deciduous climbers known as Boston ivy (Parthenocissus tricuspidata) and Virginia creeper (P. quinquefolia).
Ivy growing on trees is often thought to be a serious problem, endangering the health of even very large trees. However, its presence on the trunk is not damaging and where it grows into the crown this is usually only because the trees are already in decline or are diseased and slowly dying.
When to tolerate ivy
- On most trees that are in sound health and are not being grown for their attractive bark, ivy can be allowed to grow on the trunk without concern for the tree's health or vigour
- Ivy is not a parasite like mistletoe and does not penetrate a tree's bark or roots; the short, root-like growths which form along climbing stems are for support only. Its own root system below ground supplies it with water and nutrients and is unlikely to be strongly competitive with the trees on which it is growing. It is also found mainly on established or mature trees where, unlike young trees, some competition can be tolerated
- Ivy has much wildlife value. As ground cover in woodland, ivy greatly lessens the effect of frost, enabling birds and woodland creatures to forage in leaf litter during bitter spells. Growing on trees, it provides hiding, roosting, hibernating and nesting places for various animals, birds and insects (including butterflies), particularly during the winter months and in areas where there are few other evergreens. The arboreal form is also an invaluable late nectar source for many pollinating insects
When to consider controlling ivy
- If the branch canopy becomes thin and allows sufficient light to enter, the ivy will develop into its arboreal form. Fraxinus (ash) and Larix (larch), are both trees with a naturally thin, open crown so can may suffer heavy infestation. For this reason ivy on ash and larch trees is often controlled
- Where ivy may be a problem is with very old or damaged trees. Firstly, its dense evergreen cover may hide cavities or areas of decay. Secondly, it can become an additional weight in the canopy which, in time, could affect stability of the tree, particularly in windy conditions
- When trees are grown for their attractive stem or bark, such as birch and some acers, it is sensible to keep the stems or trunks free from ivy so as not to obscure this key ornamental feature
Note: The presence of ivy often indicates a tree in ill health, infected with honey fungus for example. This should be investigated. If you are concerned about an old or diseased tree, always seek professional advice from an arboriculturist or tree surgeon.
As ivy is not directly harmful to trees and is beneficial to wildlife, control is not usually necessary. However, where it is undesirable either by obscuring attractive bark or adding weight to an ailing tree, control will be needed.
Where possible, the stems should be cut back to the ground and the woody stump dug out. If proximity to the tree’s roots prevents removal, regular cutting of the stems to ground level may weaken the ivy over time but is unlikely to kill it.
As an unwanted ground cover
Dig up all stems and woody roots. This may be difficult on heavy soils or where vegetation is very dense. Where the site is not needed for planting, an alternative control method is to clear away all top growth before laying weed-control fabric and a 10-15cm (4-6in) deep layer of bark mulch. Leave in place for at least two growing seasons.
Glyphosate and triclopyr: Ivy that is growing vertically can be killed by severing the stem close to soil level and treating the stump with a stump and rootkiller containing glyphosate (e.g. Scotts Roundup Tree Stump & Rootkiller, Bayer Tree Stump Killer, Doff Tree Stump & Tough Weedkiller and William Sinclair Deep Root Ultra Tree Stump & Weedkiller) or triclopyr (Vitax SBK Brushwood Killer)
As an unwanted ground cover
Glyphosate: Ivy is not easily controlled by means of weedkiller sprays, partly due to the very glossy, moisture-resistant nature of its leaf surface. In this situation it is best to try the tough formulations of glyphosate (e.g. Scotts Roundup Ultra 3000, Scotts Tumbleweed, Bayer Tough Rootkill, Bayer Super Strength Glyphosate or Doff Knockdown Maxi Strength Weedkiller) or for spot treatment use Scotts Roundup Gel. It is essential to avoid spray coming into contact with the foliage or green stems of other plants, so cover adjacent plants with polythene, kept in place until the spray has dried. Bruising the leaves by trampling or with the back of a rake prior to treatment may help with the uptake of the weedkiller. Repeat treatment is usually required for good control.
Triclopyr: In rough grass areas, Vitax SBK Brushwood Killer, containing triclopyr, can be used as it should not seriously damage long grass. However, it could affect the developing growing points of bulbs, particularly if applied in late winter, causing foliage and perhaps flower distortion in the season following application. Therefore, if treating areas under-planted with bulbs, avoid run-off into the soil as much as possible.
Weedkillers for gardeners (Adobe Acrobat pdf document outlining different weedkillers available for gardeners; see sections 1a and 4)
Chemicals: using a sprayer
Chemicals: using safely and effectively
Chemicals: using spot and broad-scale weedkillers