What Are The Harmful And Harmless Growth On Trees?

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A tree is rarely alone. Tendrils climb up the trunk and branches, yellow lichens cover the bark, or mistletoe nests form packs in the crown. The additional growth gives some people the impression that the tree is being strangled by parasites.

But not every infestation is harmful. If it does not interfere with the appearance, the tree owner does not have to intervene at all in most cases. We take a look at known bark and branch infestations and tell you whether they are dangerous for the tree.

Efeu (Gattung)

Rumor has it that ivy growth is harmful to the tree. This is not so. Ivy plants take root in the soil. With the help of their sucker roots, they cling to the bark from the outside. Thus, they do not penetrate the tree and do not stress the heartwood. On the contrary, the layer of ivy protects the tree from drying out, frost and wind.

A harmful effect would exist at most if the entire tree were overgrown. In addition, there is another reason not to remove it: Ivy is a favorite breeding ground for many bird species. So come to terms with the sight, and you will also be demonstrating your love of nature.


Mistletoe is connected to the tree by its sinker roots. Through these they absorb water and nutrients. This is normally completely harmless. Only a very heavy mistletoe infestation can lead to the death of branches. In some European states, mistletoe is a protected species. They also provide opportunities for various bird species to build nests.

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Botanically, lichens are not plants, but a symbiosis of fungi and algae. The fungus forms the body of the lichen and absorbs water and minerals. It also protects the alga from damage and desiccation. The alga, in turn, produces sugars through photosynthesis, on which the fungus depends. For the tree, this does not lead to any consequences. Lichens do not penetrate deeper into the tree. Therefore, they have no effect on the growth of the bark.


Let’s move on to the real killers. And to add another truth right away: In many cases of infestation with wood-decomposing fungi, remediation is no longer possible. Such types of fungi affect the strength of the wood and, consequently, its stability and resistance to breakage.

They often penetrate the wood in the form of spores through wounds on the trunk. At the time when the fungal infestation is noticed on the basis of the fruiting bodies, felling is usually the only solution. The following species are particularly dangerous and usually lead to the death of the tree:

Giant spore fungus:

It invades through the roots and causes significant loss of vitality. The tree gets a light head and the leaves are smaller. It can also cause white rot, which leads to shredding of the wood and consequent loss of stability. The giant porling is especially feared in beech trees.

Fire-crusted fungus:

The fire-crusted fungus is a wood rot pathogen that often attacks linden or beech trees. It decomposes the heartwood in the area of the rootstock as well as the base of the trunk in a very short time. Only a few inconspicuous fruiting bodies indicate that it is actually already too late.

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Contrary to the assumption that it only spreads on dead wood, the Hallimasch also penetrates healthy wood. To do this, it uses injuries to the tree. Infestation does not necessarily lead to felling in every case. Vital trees may be able to counteract the damage automatically by nucleation.

Growing Plants

Besides fungi, there is another growth that may bring damage to the tree. However, in this case, the size of the tree is critical. Climbing plants can cause branches to break off by their weight alone.

Preventive Tree Care – What To Do If Something Is On It That Shouldn’t Be?

As mentioned earlier, there are no measures to counteract a fungal infestation after the fact. Therefore, you should act preventively. First of all, tree owners should minimize shading of the tree. High humidity promotes the formation of damaging pathogens. Appropriate pruning of the surrounding area will remedy the situation.

They should also refrain from using wound protectants after pruning. Biologists point out that the coating can sometimes crack over time or even flake off completely. Water gets in and with it the dangerous fungi. Instead of lowering it, you increase the risk of infestation.

Proper tree pruning significantly limits the risk of fungal infestation. The carefully executed work of the tree professional leaves no residual fibers or frayed areas. In addition, a knife or sharp saw is used to finish the job.


  • James Jones

    Meet James Jones, a passionate gardening writer whose words bloom with the wisdom of an experienced horticulturist. With a deep-rooted love for all things green, James has dedicated his life to sharing the art and science of gardening with the world. James's words have found their way into countless publications, and his gardening insights have inspired a new generation of green thumbs. His commitment to sustainability and environmental stewardship shines through in every article he crafts.

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