North America Native Plant

Wart Lichen

Botanical name: Pyrenula cocoes

USDA symbol: PYCO9

Habit: lichen

Native status: Native to North America  

Wart Lichen: The Tiny Garden Inhabitant You Never Knew You Had Have you ever noticed small, bumpy patches on the bark of trees in your garden or local forest? Chances are, you’ve encountered Pyrenula cocoes, commonly known as wart lichen. This fascinating organism isn’t actually a plant at all, but ...

Wart Lichen: The Tiny Garden Inhabitant You Never Knew You Had

Have you ever noticed small, bumpy patches on the bark of trees in your garden or local forest? Chances are, you’ve encountered Pyrenula cocoes, commonly known as wart lichen. This fascinating organism isn’t actually a plant at all, but rather a unique partnership between fungi and algae that creates one of nature’s most successful collaborations.

What Exactly Is Wart Lichen?

Wart lichen belongs to a remarkable group of organisms called lichens, which are composite life forms consisting of a fungus and photosynthetic partner (usually algae) living together in a mutually beneficial relationship. The fungus provides structure and protection, while the algae produce food through photosynthesis. It’s like having the perfect roommate situation that’s lasted millions of years!

This particular species is native to North America and can be found naturally occurring in eastern regions, particularly throughout the southeastern United States. You won’t find it at your local nursery because, well, you simply can’t buy it or plant it intentionally.

Identifying Wart Lichen in Your Garden

Wart lichen earned its common name from its distinctive bumpy, warty appearance. Here’s what to look for:

  • Small, crusty patches on tree bark that appear pale gray to whitish
  • Tiny black dots (called perithecia) scattered across the surface – these are the fungal fruiting bodies
  • A bumpy, warty texture that gives it its common name
  • Typically found on the bark of deciduous trees in humid environments

Is Wart Lichen Beneficial to Your Garden?

While you might initially worry about these crusty patches on your trees, wart lichen is actually a sign of good environmental health! Here’s why having it around is a positive thing:

  • Lichens are excellent air quality indicators – their presence suggests clean, unpolluted air
  • They don’t harm trees; they simply use bark as a growing surface
  • They contribute to biodiversity in your garden ecosystem
  • Some wildlife species use lichens for nesting materials

What This Means for Your Garden

If you discover wart lichen growing naturally in your garden, consider yourself lucky! It’s not something you can encourage or discourage – it simply appears when conditions are right. The lichen grows extremely slowly and establishes itself through microscopic spores carried by wind.

Since wart lichen thrives in humid forest environments, its presence indicates that your garden provides suitable habitat for native species. Rather than trying to remove it (which isn’t necessary), appreciate it as a small but important part of your local ecosystem.

The Bottom Line

Wart lichen is one of those quiet garden inhabitants that most people never notice, but it’s actually quite remarkable. This tiny organism represents millions of years of evolutionary cooperation and serves as a living indicator of your garden’s environmental health. While you can’t plant it or tend to it like your flowers and vegetables, you can appreciate its presence as a sign that your outdoor space is supporting diverse native life.

Next time you’re walking through your garden or a local forest, take a moment to look closely at tree bark. You might just spot these fascinating little partnerships doing their thing, quietly contributing to the rich tapestry of life that makes our gardens special.

Wart Lichen

Classification

Group

Lichen

Kingdom

Fungi - Fungi

Subkingdom
Superdivision
Division

Ascomycota - Sac fungi

Subdivision
Class

Ascomycetes

Subclass
Order

Pyrenulales

Family

Pyrenulaceae Rabenh.

Genus

Pyrenula Ach. - wart lichen

Species

Pyrenula cocoes Müll. Arg. - wart lichen

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