Have you ever noticed a grayish-green, leafy, or crusty growth on the bark of your crepe myrtle? That’s lichen, a unique organism that often sparks curiosity and concern among gardeners.
Is it harmful? Is it beneficial? In this guide, we will explore the fascinating world of lichen on crepe myrtles, answering all your questions and dispelling any myths.
Lichen appears on crepe myrtles and other trees when environmental conditions are favorable. It forms from a symbiotic relationship between a fungus and an alga or cyanobacterium. Lichen is not parasitic and doesn’t harm the tree. It only uses the tree as a support to get sunlight.
If you’re intrigued by the presence of lichen on your crepe myrtle or if you’re concerned about its impact, read on. We’ll explain what lichen is, its benefits, potential issues, and how to manage it.
- Lichen is a unique organism that forms from a symbiotic relationship between a fungus and an alga or cyanobacterium. It uses the tree as a support and does not harm the tree.
- A heavy presence of lichen might indicate that a tree is not growing vigorously or is in poor health.
- Lichen growth can be influenced by drought, saturated soil, compacted soil, slow growth, diseases or pests, and general tree stress.
- If you wish to remove lichen, gently scrub it off with a soft brush, but be careful not to damage the tree bark.
Curious about the diseases and pests that can impact crepe myrtle trees? You’ll find a full guide in my article, Crepe Myrtle Diseases and Pests.
Lichen on Crepe Myrtle
Lichen on crepe myrtles can be a common sight, especially in environments with clean air, as lichen is sensitive to air pollution. Here’s a closer look at this unique organism:
What Exactly Is Lichen?
Lichen is a composite organism that arises from a symbiotic relationship between a fungus and an alga or cyanobacterium.
The fungus provides a protective structure while the alga or cyanobacterium photosynthesizes to produce food.
Lichens come in various forms, colors, and sizes, and they can grow on various surfaces, including tree bark, rocks, and soil.
Lichen vs. Moss
While lichen and moss may sometimes look similar, they are different types of organisms.
Moss is a simple plant that has roots, stems, and leaves, and lichen is a composite organism formed from a symbiotic relationship.
Moss often forms a dense, green carpet and needs a moist environment to grow, but lichen can survive in drier conditions and often appears leafy or crusty.
Benefits of Lichen
Lichen is not harmful to trees. It uses the tree merely as a support to reach sunlight. In fact, the presence of lichen often indicates good air quality, as lichen is sensitive to air pollution.
Some lichens can also help to fix nitrogen from the air, contributing to the nutrient cycle.
While lichen itself doesn’t harm trees, a heavy presence of lichen might indicate that a tree is not growing vigorously.
This could be due to other underlying issues, such as poor soil conditions, disease, or pest infestation.
If you notice a lot of lichen on your crepe myrtle, it might be worth checking the tree’s health and growing conditions.
Common Lichen Species
There are several types of lichen that you might find on your crepe myrtle.
Some of the most common include foliose lichen, which has a leafy appearance, and crustose lichen, which forms a crust-like growth on the tree bark.
Fruticose lichen, which has a shrubby or bushy appearance, might also be found.
Factors Contributing to Lichen Growth
Lichen growth on crepe myrtles can be influenced by several factors. Here’s what you need to know:
1. Drought Leading to Root Loss
Drought conditions can lead to root loss in trees, which can slow down the tree’s growth. This can create favorable conditions for lichen, which thrives on slow-growing or stressed trees.
During prolonged dry periods, the tree’s ability to take up essential nutrients and water is compromised, leading to stress and reduced growth.
This slower growth rate can provide an opportunity for lichen to establish itself on the bark.
2. Saturated Soil Suffocating Roots
Conversely, soil that is too wet can suffocate tree roots, leading to stress and slow growth. Good drainage is essential to prevent this issue.
Overly saturated soil can deprive the roots of oxygen, a condition known as waterlogging. This can lead to root death, reduced nutrient uptake, and ultimately, a stressed and slow-growing tree.
As with drought, these conditions can create an environment conducive to lichen growth.
3. Compacted Soil Limiting Root Growth
Compacted soil can limit root growth, leading to a stressed and slow-growing tree. If your soil is compacted, consider aerating it to improve conditions for your tree.
Compacted soil has reduced pore space, limiting the amount of air and water that can reach the tree’s roots. This can lead to poor root development, reduced nutrient uptake, and slower growth.
Again, these conditions can favor the growth of lichen on the tree’s bark.
4. Slow Growth
Trees that are naturally slow growing or are growing slowly due to suboptimal conditions can often have more lichen. This is simply because the lichen has more time to establish itself on the bark.
Factors contributing to slow growth could include inadequate sunlight, poor nutrition, unsuitable soil pH, or the tree’s natural growth habit.
5. Diseases or Pests
If a tree is affected by diseases or pests, it may become stressed and grow more slowly, which can encourage lichen growth. Regularly check your crepe myrtle for signs of disease or pest infestation.
Diseases such as powdery mildew or pests like aphids or scale can weaken the tree, leading to slower growth and providing an opportunity for lichen to establish.
6. General Tree Stress
Any form of stress can slow down a tree’s growth and make it more susceptible to lichen growth. This includes factors like poor nutrition, inadequate sunlight, and unsuitable soil pH.
Ensuring that your tree has the right growing conditions, including the right amount of sunlight, a suitable soil type, and adequate nutrients, can help to reduce stress and promote healthy growth.
While lichen doesn’t harm trees, you might wish to manage it for aesthetic reasons or if you’re concerned about the health of your tree.
Regularly monitor your tree’s health and address any issues promptly. If you wish to remove lichen, gently scrub it off with a soft brush, but be careful not to damage the tree bark.
Does Lichen Kill Trees?
No, lichen does not kill trees. It is not a parasite and does not take nutrients from the tree. Instead, it uses the tree as a support to reach sunlight.
If you find it unsightly, you can remove it by gently scrubbing it off with a soft brush, but removal is not necessary.
Is Spanish Moss on Crepe Myrtle Bad?
Spanish moss is not harmful to crepe myrtles. Like lichen, it uses the tree as a support and does not take nutrients from the tree. There is no reason to remove it other than for aesthetic reasons.
Lichen on crepe myrtles is a fascinating subject. While it might cause concern among some gardeners, it’s important to remember that lichen itself is not harmful to trees.
In fact, its presence often indicates good air quality and can contribute to the nutrient cycle.
However, a heavy presence of lichen might indicate that a tree is stressed or in general decline, so it’s always a good idea to check your tree’s health and growing conditions.
With the right care, your crepe myrtle can coexist with lichen and continue to thrive.
Like most trees, Crepe Myrtle is susceptible to various pests and diseases. Here are a few others to learn about: