In spring, for example, the foliage provides a shelter for insects as well as breeding opportunities for birds such as blackbirds, wrens, summer goldcrests or the chiffchaff. In the fall, ivy is very important as a food source for insects because it blooms from September until late in the fall, when most other plants have faded and no longer provide nutrient-rich nectar. Among the many visitors to ivy flowers during this time are hoverflies, ladybugs, butterflies such as the admiral, ants, bees, wrinkled wasps, solitary wasps, or firebugs. However: only when the ivy has reached about 20 years of age and has not been pruned too much, it forms flowers. In winter, the berries are a popular food source for birds such as blackbirds, thrushes or starlings.
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Ivy is not a parasite
There are many myths about ivy. However, contrary to popular belief, the climbing plant is not a parasite; it does not extract nutrients or water from trees, nor does it secrete harmful substances. Ivy simply needs a support to grow in height. In fact, the lush growth of ivy can become a problem for small or weak trees if it overgrows and darkens them. But for mature trees, there is no danger of collapse and the ivy plant even has a positive effect. For example, its dense foliage protects the tree from direct sunlight and evaporation in summer and from frost in winter.
That ivy can grow into the tree, suffocate or strangle it, is also a misconception. Close observers will note that there is no ingrowth. Likewise, there is no competition for light, as ivy grows in the area known as the shade canopy, which accounts for only one-third of the tree’s photosynthetic output.
Also valuable in the city center
In the inner city with few open spaces, ivy walls are also significant small biotopes and guarantors of biodiversity. In addition, they have outstanding positive local climatic, air-purifying and naturally aesthetic aspects. Similar to trees, ivy foliage mitigates temperature extremes and filters fine dust from the air. Since the plant makes few demands on soil, light and water supply – it just must not be too dry – it still grows well even where there is no room for trees. From both an ecological and urban climatic point of view, it is therefore decidedly disadvantageous that ivy is apparently on the list of undesirable plants in green maintenance and is mercilessly cut down wherever it ventures too far up the hill.
Time and again, ivy (Hedera helix) is suspected of damaging the trees on whose trunks it climbs or even causing them to die. However, scientific studies from Europe and Europe do not confirm these assumptions. On the contrary – ivy is a visual and ecological enrichment of trees in our gardens, parks and forests. Therefore, measures for the general removal of ivy from trees in our villages and towns should be rejected.
The ivy in the dock….
Many people unfortunately believe that ivy is responsible for damage or even death of trees. They suggest that ivy is boring its roots like a parasite into the trunk of the tree it is climbing and tapping into its conduit pathways, that the tree is being cut off from air and water by the ivy, or that the ivy is depriving the tree of all nutrients and water in its root zone. They use these alleged arguments to remove this native climbing plant that can live up to 400 years.
In general, ivy poses no threat to our trees. This is confirmed by scientific studies from all over Europe (see below paper of the BUND-Landesverband Hannover). Only smaller woody plants such as fruit trees or large shrubs such as hawthorn can be overgrown and darkened if ivy is allowed to grow completely unhindered. In individual cases, the risk of wind and snow breakage may possibly increase, especially if the tree is already damaged.
Ivy as a habitat
Ivy is an important component of biotope and species conservation. It provides habitat for birds and insects. In the fall, the inconspicuous yellow-green ivy flowers are one of the last food sources for bees and other insects. In winter, our wintering bird species feed on the blue-black fruits of the ivy in otherwise often bare gardens.
Besides, the evergreen ivy enlivens our gardens even in winter and makes gray concrete walls or garbage cans disappear all year round.
In many gardens and parks with old trees, you can sometimes see lush ivy vines climbing up the trees with hardly anything left of the trunk below. Since ivy is a root climber, the question of potential damage arises: Is the tree suffocating under the growth? Do the roots of the two plant species compete with each other? Do you really always have to remove ivy?
The common ivy as a greening of areas and trees.
The common ivy (Hedera helix) is the only root climber of the native flora. It can creep far or climb up to 30 meters with the help of its adhesive roots. The plant is as popular as a ground cover as it is as a climber for greening walls, facades and tree trunks. Hedera helix is also important as an insect pasture, because the yellow-green flowers that appear between September and October are rich in nectar. This is readily accepted by wasps, flies and numerous other insects. The blue-black, poisonous fruits ripen in spring.
Does a growth of ivy harm?
Many gardeners believe that ivy, because of its roots, penetrates deep into the bark of the tree, damaging it. However, in fact, the plant adheres only superficially and only on the surface of older trees with strong bark and bark. The roots of ivy do not penetrate the wood, do not injure the tree, and do not extract nutrients from it. In addition, ivy is a shade plant that prefers to grow on trees with dense foliage and a broad crown. Therefore, the climbing plant does not appear as a light predator, especially since it rarely penetrates into the crowns and overgrows them. In summary, it can be said that the growth of ivy does not harm the tree – in principle, anyway.
When you should remove ivy – and when you shouldn’t
Older, healthy trees are not harmed by an overgrowth of ivy. However, the situation is different with young trees whose bark is still thin. Here, too, the roots of the ivy do not penetrate, but the growth creates a favorable environment for the growth of fungi – which, in turn, penetrate through the still fragile bark. For the same reason, trees with damaged bark are also at risk from ivy. Furthermore, ivy should be removed from trees with thin branches, as they often cannot support the extra weight. Fruit trees are also not suitable hosts, as the insects that live in the ivy (such as wasps) can have a negative impact on the harvest.
In forests, parks and gardens, you can always see trees lush with ivy (Hedera helix). Many people enjoy this year-round living greenery, but others worry whether the lianas will not harm the tree in the long run. Therefore, it happens again and again that the saw is used and ivy growth on trees is brought to death. The “tree friends” and ivy enemies are found both among private people, who proceed on their properties or in criminal own initiative also on public surfaces against ivy, and – still – in authorities.
What is there to the fear that ivy can become a tree killer? We explored this question with an evaluation of the current state of research.
In general, ivy poses no threat to our trees. Only smaller trees, such as apple and pear trees, and large shrubs, such as hawthorn, can be overgrown and darkened by ivy if left to grow completely unchecked. In isolated cases, especially if the tree has been previously damaged, the risk of wind and snow breakage may increase. However, studies from forests in England, France, Europe, and Italy, where ivy was allowed to grow unimpeded for long periods of time, showed no negative effects of ivy growth on our large native trees. On the contrary, two studies even demonstrated greater growth and thus apparently greater vitality of trees overgrown with ivy.
As an evergreen liana and the only fall bloomer of our native woody plants, ivy is a special feature of our flora, making it very valuable not only to the landscape but also to wildlife. It can live for several centuries, rivaling our longest-lived trees.
Old ivy plants, much like old trees, deserve special protection. To cut them above the ground and let them die creates a bleak sight in the long run, not only because of the ivy corpses hanging in the tree. This method is also completely unprofessional and creates new dangers. If ivy on trees should really be a problem in an individual case, it is usually sufficient to reduce the growth in the crown. It is to be wished that actions for general ivy control on trees finally belong to the past.
Ivy does not ‘choke’ the trees
However, this is not so. Ivy that climbs to the light on large trees does not harm the trees. The trees are not ‘suffocated’ by the stranglehold of the climbing plants. There is also a reason for this: because the adhesive roots of the ivy do not penetrate the bark of the trees. This means that the ivy does not draw its nourishment (water) directly from the tree, it only uses it as a climbing aid.
Since the ivy is still rooted in the ground, it feeds itself through those roots. This has apparently not even penetrated to all green space offices at present. Thus they provide again and again by cutting the ivy at the trunk for partial very unattractive views at the trees in large parks.
In addition, ivy rarely grows up to the treetops, so there is usually enough light left for the trees.
Now we come to the big exception: young trees often have very thin bark, which does not protect them sufficiently from the adhesive roots of ivy. Then the trees can actually suffer damage.
It is also advisable to remove the ivy from fruit trees, because insects often feel very comfortable in it, which can tamper with the fruit. This means crop losses. If trees are already weakened or have damaged bark, removing ivy may be an option.
By the way: Ivy can cause damage to house walls. Its adhesive roots make it into the smallest cracks in walls. If they then grow and become thicker, this can cause cracks in the plaster, which in turn can have expensive consequential costs.
