Q: Can a tree be damaged or killed if it has ivy climbing the trunk?

A: The answer from the American Ivy Society is NO.
When people look at deciduous trees in winter and see evergreen ivy growing up the tree trunks, they incorrectly assume that the ivy (Hedera) is taking over the tree, or damaging or even killing the tree. Ivy is not a parasite but simply attaches to the trunk by means of adventitious roots that cling to the surface of the tree’s bark. The roots do not penetrate the bark which is a non-living, outer protective layer of a tree. Nor does ivy grow into the leafy outermost layer of a tree (the canopy) and smother a tree or prevent photosynthesis. Ivy grows on the trunk of a tree and, when the tree declines because of disease or old age, the ivy may develop at the uppermost tips of the vines into a bushy, mop head that is confined to the interior of a tree.

Vines, particularly ivy that is confined to the interior of a tree, do not damage healthy trees. However, trees that are weak-wooded or in decline and have any kind of vines on them may be damaged in wind and ice storms as has been documented for grapevine (Siccama et al, 1976). When dead tree limbs fall to the ground and decompose into nutrients, these nutrients are taken up by other surrounding plants. This phenomenon is part of the recycling of nutrients that takes place in a forest ecosystem. Even nutrients taken up by ivy are returned to the soil as the ivy leaves are shed and decompose thus adding nitrogen to the soil to be used by the neighboring trees. Although ivy is an evergreen, it does shed its leaves but not all at once. Only ivy leaves that are 2-4 years are shed annually but, since the new leaves remain, ivy is evergreen..In Europe, where ivy is native, ivy researchers have been observing ivies on trees for years. Respected ivy expert Br. Ingobert Heieck in Heidelberg, Germany pointed out (1990) that ivies, which are confined to the trunks of trees, flourish when the trees decline (often from disease, or old age) and the ivy takes advantage of the thinned or now-opened canopy to become adult. That ivy does not damage healthy trees has also recently been pointed out by British ivy authorities Peter Rose (1996), Stephen Taffler (1990) and author Fearnley-Whittingstall (1992).

Literature Cited:

Fearnley-Whittingstall, Jane. 1992. “False Accusations.” pp. 7-10.

Ivies. Random House. New York. 160 pp.

Heieck, Ingobert. 1990. Was man vom Efeu noch wissen sollte. pp. 31-33. IN: Der Efeu auf unseren Friedhöfen. Gärtnerei Abtei Neuburg. Heidelberg, Germany. 34 pp.

Rose, Peter Q. 1996. [Ivy in…Architecture}. p. 21. IN: The Gardener’s Guide to Growing Ivies. Timber Press. Portland, Oregon. 160 pp.

Siccama, T.G; Weir, G.; and K. Wallace. 1976. Ice damage in a mixed hardwood forest in Connecticut in relation to Vitis infestations. Bulletin of the Torrey

Botanical Club 103: 180-183.

Taffler, Stephen. 1990. In Defence of Ivy. p. 97. IN: Climbing Plants and Wall Shrubs. Crowood Press. Swindon, Wiltshire, England.
128 pp.

Sabina M. Sulgrove, PhD
Taxonomist, American Ivy Society


Will the ivy damage/injure the trees?

Q: I live in Olympia Washington. I have a rental property that I haven't seen for awhile. I went over to repair something for the tenant and was surprised to see the amount of ivy everywhere.

Sorry I don't know the kind. My concern is that it is growing up many Douglas Fir trees. Do you think the ivy will be detrimental to the Douglas Fir over time? Many trees are almost surrounded and the ivy has grown to pretty tall heights (on the tree trunks).

It looks nice and I don't want to destroy the growth unless it will cause problems for the trees. The ground cover ivy is fine.

A: Generally speaking, ivies do not damage healthy trees. However, in your part of the country there are some types of Hedera that have become rather invasive as they love the climate and grow very rapidly. My recommendation to you is that you should develop a regular program of trimming the ivy and keeping it in check. You will probably need to prune it back about twice per year. I would suggest you prune in early spring and late summer.

If you like the ivy climbing on the trunk of the tree perhaps you could allow it to climb to a manageable height and then prune it off so that it does not get out of control and take over the canopy of the trees. I must also caution you to keep the ivy ground cover restricted to your property. Some types of ground cover ivy can become a problem if allowed to escape to
natural surroundings.