North America Native Plant

Wart Lichen

Botanical name: Pyrenula punctella

USDA symbol: PYPU4

Habit: lichen

Native status: Native to North America  

Wart Lichen: The Tiny Garden Guardian You Never Knew You Had Have you ever noticed small, dark, bumpy growths on the bark of trees in your yard and wondered what they were? Meet the wart lichen (Pyrenula punctella), a fascinating organism that’s probably been quietly doing good work in your ...

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

Have you ever noticed small, dark, bumpy growths on the bark of trees in your yard and wondered what they were? Meet the wart lichen (Pyrenula punctella), a fascinating organism that’s probably been quietly doing good work in your garden without you even realizing it!

What Exactly Is Wart Lichen?

First things first – wart lichen isn’t actually a plant at all! It’s a lichen, which is a remarkable partnership between a fungus and algae working together as one organism. Think of it as nature’s ultimate roommate situation, where both partners benefit from the arrangement. The fungus provides structure and protection, while the algae photosynthesizes to create food for both.

Pyrenula punctella gets its common name from its distinctive warty, bumpy appearance on tree bark. These small, dark growths might not win any beauty contests, but they’re absolutely fascinating once you know what to look for.

Where You’ll Find This Native Treasure

Wart lichen is native to North America, with a range primarily in the eastern United States, particularly thriving in the southeastern regions. You’re most likely to spot it growing naturally on the bark of various tree species in woodland areas and mature landscapes.

How to Identify Wart Lichen

Spotting wart lichen is easier than you might think once you know what to look for:

  • Small, dark, warty bumps on tree bark
  • Typically black or very dark brown in color
  • Grows in scattered patches rather than covering large areas
  • Found on the bark of living trees, not fallen logs
  • Size ranges from tiny pinhead-sized bumps to small pea-sized growths

Is Wart Lichen Beneficial to Your Garden?

Absolutely! While wart lichen might not add traditional ornamental value to your landscape, it serves as an excellent indicator of environmental health. Here’s why you should appreciate having it around:

  • Air quality indicator: Lichens are sensitive to air pollution, so their presence suggests you have relatively clean air
  • Ecosystem health sign: A diverse lichen population indicates a healthy, balanced environment
  • Wildlife support: While not a major food source, lichens can provide nesting materials for some small creatures
  • Natural beauty: Once you start noticing them, lichens add subtle texture and interest to tree bark

What This Means for Your Garden

Unlike traditional garden plants, you can’t plant or cultivate wart lichen. It appears naturally when conditions are right, and that’s actually a good thing! If you’re seeing wart lichen (and other lichens) in your yard, pat yourself on the back – it means your garden environment is healthy enough to support these sensitive organisms.

Should You Be Concerned About Lichens on Your Trees?

Here’s some good news: wart lichen won’t harm your trees! Lichens are epiphytes, meaning they simply use the tree bark as a surface to grow on without taking nutrients from the tree itself. They’re not parasites, and they won’t cause damage to healthy trees.

In fact, if you notice lichens suddenly disappearing from your trees, that might be more cause for concern than their presence, as it could indicate declining air quality or environmental stress.

Encouraging Lichen Diversity in Your Landscape

While you can’t plant wart lichen directly, you can create conditions that support lichen diversity:

  • Maintain mature trees with varied bark textures
  • Avoid using harsh chemicals or pesticides that might affect air quality
  • Keep your landscape relatively natural rather than overly manicured
  • Be patient – lichens grow slowly and establish over time

The Bottom Line

Wart lichen might not be the showstopper you’d choose for your garden’s focal point, but it’s a valuable indicator of environmental health and a fascinating example of nature’s cooperation. Next time you’re walking through your yard, take a moment to appreciate these tiny partnerships quietly thriving on your trees. They’re proof that your garden is supporting a complex, healthy ecosystem – and that’s something worth celebrating!

So while you won’t find wart lichen at your local nursery, you might just discover it’s already made itself at home in your landscape. And now that you know what to look for, you can enjoy the satisfaction of spotting these remarkable organisms and knowing they’re a sign of your garden’s good health.

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 punctella (Nyl.) Trevis. - 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