Is Lichen on Trees Unhealthy?

What Is That Growing on My Tree?

When you first catch a glimpse of the development on your tree trunk or branches, you may find yourself wondering about the type of plant that’s growing. The next question may be to ask if lichen on trees is good or bad. Is it something you need to worry about or is healthy for the tree? First, lichen is actually not a plant. Lichen is a corresponding and symbiotic relationship between fungi and algae or bacterial growth. The algae/bacteria uses photosynthesis to sustain the growth of the fungus and the fungus “protects” the green or blue-green algal growth below it.

Second, it’s not tree specific, but trees offer a unique and stable way to support the growth and expansion of lichen. Lichen does best when it has a hard and slightly porous or “graspable,” “attachable” surface. There are no roots, so there’s no burrowing. Lichen will attach itself to anything sturdy and stationary and to which it can comfortably hold on and propagate. Lichen will survive through much of what plants cannot. It will be seen “coming through” after fires and can be found on rocks, fences, and headstones, in addition to trees.

We know that there are over 20,000 different kinds, and they’re visually different. They can be found all over the world, from warm and humid forests to barren and icy areas. They can even manage to survive in dry and arid regions. They will grow on virtually any surface.
While their existence and growth may seem like an infestation of some sort, they’re actually nonparasitic and colonize, rather than overthrow. Their existence can, however, suggest that there may be some underlying issues with the tree in terms of vitality, but that is something to be researched for individual cases.

What Is Lichen and What Does It Look Like?mr-tree-is-lichen-on-trees-unhealthy

As we’ve said, lichen are not plants, they do not have roots, nor do they have leaves or flowers in season. It can grow on trunks, leaves, shrubs, or other parts of trees. There are a few different hues it comes in, including a grayish or blue-green scaly or patchy. It can appear crusty and may sometimes hang or gather in bunches on trees or limbs.

How Does It Form?

Many of the varieties in this group, whether they’re moss, algae, or lichen, are found in a somewhat darker, damp place. It might be a perpetually shady, consistently damp, or moist place. They need dampness and moisture not only to grow but also to reproduce.

They’re a mostly adaptable species that can survive and potentially thrive in unconventional places where the normal components of life might now be accessible. That is, they’re so adaptable that sometimes lichen is found in damp places where there are limited nutrients or even where a consistent water/moisture source are inaccessible. As lichen does best in more remote or rural areas, you’re likely to see more of the colonizing lifeforms on hard and supportive posts and trees outside of urbanized areas.

Where Do They Thrive?

  • Sometimes weak branches and parts of the tree that are lacking in vigor can be found to be susceptible to colonization. While not always true, the presence of the lichen are blamed on the “unwellness” or state of the tree.
  • If there are parts of your tree that haven’t been treated as well as they should have been, there are sometimes indicators that come out on the form of lichen.
  • If there’s a lot of “overcrowding” on branches or trees, this can be a time and location where lichen can populate.
  • Lichen can even appear on vigorous “new” plants or trees in some more moist and humid regions.
  • Taking into account the “normal” direction from which rain and moisture exposure comes, this can indicate the place where most of the lichen growth may take place.
  • Finally, the side of the tree with minimal or decreased exposure to the sun will likely bear more of the brunt of the lichen. If there’s a sunward-facing patch of lichen, it will often turn a bit more red-gray or copper rust-tinted color.


There really isn’t a specific mode or matter that will control or contain an outbreak of lichen. To be honest, there’s not a whole lot to worry about, but for the sake of aesthetics and the health of the plant or tree, there are a couple of ways in which to care for the removal of the lichen. At the moment, there aren’t really any reliable chemical procedures without risking life around the lichen, so there should be manual extraction or forethought about pruning and making sure that the exposed areas have more access to sunlight and the ability to grow, even among the over-darkened and damp parts of the tree.


As mentioned, there aren’t a lot of control measures available that don’t risk the current life of the tree, shrub, or other life-form on which the lichen has propagated. That being said, there are certainly ways that gardeners and tree-lovers alike can “safeguard” their trees and garden life against excessive lichen, moss, or algal growth. It is important to trim and prune trees as necessary. While the growth of lichen on trees isn’t necessarily unhealthy, there are ways to tend to the trees before the growth sets in and therefore give your tree a longer-lasting advantage in its overall well-being.

Beyond pruning, you can diagnose and care for the affected tree or branches and see what can be done to benefit the system overall and see that everything is tended to. Prevention is the best medicine, and you’ll be able to help your trees along by making sure they have strong bases with enough nutrients, fertilizing, and watering. Ensuring the vigor of the plant or tree will help protect it in the long-run against lichen and other fungi-algal species that may enjoy a new host.

Mr. Tree is an expert at not only tree management and maintenance but also diagnosis and care. Should there be any concern about the “new additions” in your yard, don’t hesitate to contact us with any questions about reinvigorating your yard or property.

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