Native Plants

Cinnamon Astrothelium Lichen

Astrothelium cinnamomeum

USDA symbol: ASCI11

North America: native

Have you ever noticed small, crusty patches on tree bark and wondered what they were? You might have been looking at a lichen like the cinnamon astrothelium lichen (Astrothelium cinnamomeum), a fascinating organism that’s more complex than it first appears. While you can’t exactly plant this little guy in your ...

Cinnamon Astrothelium Lichen: A Tiny Forest Treasure You Can’t Plant

Have you ever noticed small, crusty patches on tree bark and wondered what they were? You might have been looking at a lichen like the cinnamon astrothelium lichen (Astrothelium cinnamomeum), a fascinating organism that’s more complex than it first appears. While you can’t exactly plant this little guy in your garden, understanding what it is and why it matters can deepen your appreciation for the intricate web of life in your landscape.

What Exactly Is a Lichen?

Before we dive into the specifics of cinnamon astrothelium lichen, let’s clear up what a lichen actually is. Despite what many people think, lichens aren’t plants at all! They’re actually a partnership between a fungus and an algae (and sometimes cyanobacteria too). Think of it as nature’s ultimate roommate situation – the fungus provides structure and protection, while the algae makes food through photosynthesis. Pretty neat, right?

The cinnamon astrothelium lichen belongs to a group called crustose lichens, which means they form thin, crusty patches that are tightly attached to their surface – in this case, tree bark.

Where You’ll Find This Native Beauty

Cinnamon astrothelium lichen is native to North America, where it quietly goes about its business on tree bark in forested areas. You’re most likely to spot it in natural woodland settings rather than urban environments, as it tends to prefer the cleaner air found away from heavy pollution.

How to Identify Cinnamon Astrothelium Lichen

Spotting this lichen takes a keen eye, as it’s quite small and can easily be overlooked. Here’s what to look for:

  • Forms thin, crusty patches on tree bark
  • Appears as small, somewhat circular or irregular patches
  • Has a cinnamon or brownish coloration (hence the name!)
  • Sits flush against the bark surface and can’t be easily peeled off
  • May have tiny, raised bumps or structures on its surface

Is It Beneficial to Have Around?

Absolutely! While you can’t cultivate cinnamon astrothelium lichen like you would a flower or shrub, its presence in your landscape is actually a good sign. Here’s why this little lichen is worth celebrating:

  • Air quality indicator: Lichens are sensitive to air pollution, so finding them suggests your local air quality is relatively good
  • Ecosystem support: They provide food and habitat for tiny insects and other small creatures
  • Soil building: Over very long periods, lichens help break down rock and bark, contributing to soil formation
  • Natural beauty: They add subtle texture and color variation to tree bark

Why You Can’t (and Shouldn’t Try to) Grow It

Unlike the plants in your garden, you can’t simply purchase cinnamon astrothelium lichen at a nursery or grow it from seed. Here’s why:

  • Lichens grow extremely slowly – we’re talking years to decades to establish
  • They require very specific environmental conditions that are nearly impossible to replicate artificially
  • They’re incredibly sensitive to air quality, chemicals, and disturbance
  • The complex relationship between fungus and algae makes cultivation impractical

Supporting Lichens in Your Landscape

While you can’t plant lichens directly, you can create conditions that encourage them to show up naturally:

  • Preserve mature trees: Lichens need time to establish, so older trees are more likely to host them
  • Avoid chemical treatments: Skip fungicides and other harsh chemicals near trees
  • Maintain clean air: Support practices that reduce air pollution in your area
  • Leave dead branches: When safe to do so, leaving some dead wood provides additional surfaces for colonization

The Bottom Line

Cinnamon astrothelium lichen might not be the showstopper you can add to your garden bed, but it’s a fascinating example of nature’s complexity and cooperation. If you’re lucky enough to spot these tiny crusty patches on trees in your area, take a moment to appreciate the intricate partnership between fungus and algae that makes their existence possible. And remember – their presence is actually a compliment to your local environment’s health!

So the next time you’re walking through a wooded area or examining the bark of mature trees, keep an eye out for these subtle but important members of North America’s native ecosystem. You might not be able to plant them, but you can certainly celebrate them.

Astrothelium cinnamomeum is also known as...

Often we refer to plants by their common names. When shopping for plants the scientific name is the best way to positively identify the plant species you desire. But some plants have more than one name! While it doesn't happen often, nurseries might display one name while you're searching for another. Astrothelium cinnamomeum is also known as:

Astrothelium conicum auct. | USDA symbol: ASCO48

Why do some plants have more than one name? Over time plant species may be renamed for a few reasons:

  1. Botanists in different regions named the same plant without knowing it had already been classified.
  2. A species was reclassified after scientific advances in, for example, DNA analysis.
  3. Slight variations within a species are sometimes mistakenly identified as entirely new species.

Classification

Group: Lichen
Kingdom: Fungi - Fungi
Division: Ascomycota - Sac fungi
Class: Ascomycetes
Order: Pyrenulales
Family: Trypetheliaceae Eschw.
Genus: Astrothelium Eschw. - astrothelium lichen

Species: Astrothelium cinnamomeum (Eschw.) Müll. Arg. - cinnamon astrothelium lichen

Plant data source: USDA, NRCS 2025. The PLANTS Database. https://plants.usda.gov,. 2/25/2025. National Plant Data Team, Greensboro, NC USA