english ivy

[Ira]

I have english ivy growing up a maple tree. Will the ivy cause any harm to the tree?

[paghat]

A healthy tree in general cannot be harmed by ivy clinging to the trunk. The clinging-roots do not burrow under the bark, do not draw nutrients from the tree, do not strangle the tree. But compared to, say, climbing hydrangea or clematis, there are some potential hazards from ivy, especially if unrestrained.

Ivy can over add so much weight to a tree that it increases the possibility of of breaking loose bark & limbs. If it is not restricted to the trunk, but has spread out into the canopy, it increases the chance of blow-down in high winds, & especially in stormy areas adds risk. Ivy also increases limb loss in high winds. Ivy increases these risks by increasing the tree's wind resistance. It is recommendable to remove at least any ivy that climbs away from the trunk, as that which clings to the trunk per se does not increase wind resistance.

Ivy that has spread into the canopy can out-compete the tree for sunlight.

Ivy can hide tree-killing infestations, funguses, & diseases that are treatable if spotted in time, but won't be spotted beneath the ivy. Trees that are already ill or near the end of their lives, but which might have had a decade or so of attractive life left in them, may have their time shortened by ivy, by harboring bacterial disease or by providing a haven for an increasing number of insects, some of which are harmful to trees. Ivy that is doing especially well in a tree can be an early sign that the tree is sick, & can hasten the development of disease, but it is not the cause of the sickness. Heavy infestation of ivy is to be regarded as evidence that the tree is in a natural state of decline.

Though ivy does extremely well in shade, it in general only produces flowers & seeds when in full sun, & so seeks to get out of the shade by climbing trees. It is especially fond of climbing up dying trees, because aging or sickly trees produce fewer leaves, permit more light through, which the ivy likes. Often ivy is seen thick upon a dead tree & it can look as though the ivy must've killed the tree, but the ivy was merely an opportunist seeking to get more sun;

English ivy is an invasive competitor harmful to our native forests, though only if it begins to flower & seed. In order to flower, parts of the ivy must go through genetic change which occurs only in bright sun. An undergrowth of ivy in deep shade rarely if ever goes through the metamorphosis required to produce flowers then seeds which birds scatter into native woodlands. But ivy that has reached the upper canopy of a tree & is in full sun frequently develops upright "bushy" parts that poke straight up out of the cannopy like trees on top of trees. This is he part of the ivy that will flower, & will be too high up to keep them from going to seed, & only then poses a threat to native woodlands. For this reason all flowering ivy should be removed from ANYwhere in the garden, but won't even be noticed in the tree canopy.

Of course, if you live in England where it grows native, this is not an issue, as excess ivy in declining trees is one of the preferred habitats for sundry species of birds, bats, squirrels, etc. In England it is illegal to damage or interfer with bat roosts, including trees with lots of ivy. But here in the northwest where ivy is not natural to the forests it invades, programs have been undertaken to remove English ivy which eradicates sensitive native species in its path, & many landscapers have "taken the oath" never to plant what has become an invasive pest. Dwarf cultivars & variegated forms of ivy are not invasive, but large-leafed plain english ivy should not be planted or preserved.

-paghat the ratgirl

[Phisherman]

This has been discussed before. I asked an arborist this question, and he said emphatically, "No!" I am allowing English ivy to grow up a pine tree, so that the deer won't eat the ivy (as they do every winter).

[Vox Humana]

I have tried growing English ivy on a troublesome slope but each winter the deer strip it clean and it takes a long time to recover. I have some growing on tuteurs that flank my garage. I know that winter is almost over when the deer get hungry enough to start eat that ivy.

[Phisherman]

One effective way to protect from the deer is to use bird netting over it. Last winter the deer ate the tops of my azaleas so I had very few blooms this year. :(

[Vox Humana]

They got mine also. It was a long, cold winter here without much snow. They ate the bergenia and I thought it was gone. It has recovered nicely, but I didn't get a single flower in the spring because not a single leaf survived. I wish they would eat all my liriope because I have to cut it back to the ground anyway each spring.

[Mike LaMana]

Paghat is DEAD ON. I hate seeing this stuff in trees. It is an obnoxious, invasive weed that transpires a great deal of moisture out of the ground, year round. It belongs in Europe IMO...preferably France. Mike.