IVY ON TREES
QUESTION
Can a tree be damaged or killed if it has ivy climbing the trunk?
ANSWER
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?
QUESTION
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.
ANSWER
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.
Should I remove it?
QUESTION
I planted a great deal of ivy, covering large portions of my property. Over time it has attached itself to a number of trees, growing steadily of the trunks. Will the ivy damage/injure the trees i.e. should I remove it?
ANSWER
Generally speaking, Ivy will not damage trees. It does not take moisture from the trunk or invade the trunk in any way. There are a few words of caution. In some parts of the country -- Oregon and Washington are good examples----ivy grows so vigorously that it can become invasive and over take some trees. In most parts of the country this is not a problem as the ivy grows slowly and does not over take the canopy of a healthy and vigorous tree since that same canopy does not allow enough light in for the ivy.
However, there are some fast growing short lived trees. When there trees get older the canopy opens and allows light to come in thus encouraging the ivy to grow. The ivy can over take these trees in decline and probably shorten their life somewhat. Often gardeners allow the ivy to climb the trunk of the tree but prune it back twice per year to keep it at a manageable height. If you like the ivy on your tree and allow it to remain -- remember to water the tree and ivy
well to give sufficient water to both.
QUESTION
I have a high bank waterfront lot in Puget Sound with Douglas Fir trees. Would English Ivy help preserve the bank? Would the ivy harm the trees since it would be difficult to keep it off the trees?
ANSWER
To answer your question directly, Ivy would be a great ground cover to help preserve your bank. However, in the Northwest some types of ivy have become an invasive problem to the woodland and urban landscape. Ivy loves the climate and grows rapidly. Since winters are mild the ivy is rarely frosted and killed back to keep it in check. Also, it progresses rapidly into the adult stage, blooms and sets seed which the birds distribute freely.
Although we love our favorite plant and do promote it vigorously in most locations in the United States we do feel it is our responsibility to caution you about growing ivy in your location. It would be a great container plant where you could keep it controlled but I would not
recommend planting it to preserve the bank. Perhaps our best advice would be to check with your local Agricultural Department, Master Gardeners, or your local public gardens. I am sure they would help you find the right plant for your needs.
