North America Native Plant

Wart Lichen

Botanical name: Pyrenula lucifera

USDA symbol: PYLU3

Habit: lichen

Native status: Native to North America  

Wart Lichen: The Tiny Ecosystem Living on Your Trees If you’ve ever taken a close look at the bark of trees in your yard, you might have noticed tiny black dots scattered across the surface. Meet the wart lichen (Pyrenula lucifera), a fascinating organism that’s probably been quietly living in ...

Wart Lichen: The Tiny Ecosystem Living on Your Trees

If you’ve ever taken a close look at the bark of trees in your yard, you might have noticed tiny black dots scattered across the surface. Meet the wart lichen (Pyrenula lucifera), a fascinating organism that’s probably been quietly living in your landscape all along!

What Exactly Is Wart Lichen?

Despite its name, wart lichen isn’t actually a plant at all. It’s a lichen – a remarkable partnership between a fungus and algae that work together to create something entirely unique. The wart part of its name comes from those distinctive little black bumps (called perithecia) that dot its surface, giving it a slightly warty appearance.

Wart lichen is native to North America and forms thin, crusty patches on tree bark. It’s what scientists call a crustose lichen, meaning it grows flat against its host surface like a living paint job.

Where You’ll Find It

This hardy little organism calls eastern North America home, thriving in temperate forest regions where clean air and suitable tree hosts are abundant.

Is Wart Lichen Good for Your Garden?

Absolutely! While you can’t plant or cultivate wart lichen (it does its own thing), having it show up naturally in your landscape is actually a wonderful sign. Here’s why you should welcome these tiny tenants:

  • Air quality indicator: Lichens are sensitive to air pollution, so their presence means you have relatively clean air
  • Harmless to trees: Unlike some organisms, lichens don’t damage their host trees – they just use the bark as a place to live
  • Adds biodiversity: Every lichen contributes to your local ecosystem’s complexity
  • Low maintenance: They require absolutely zero care from you

How to Identify Wart Lichen

Spotting wart lichen is like going on a tiny treasure hunt. Here’s what to look for:

  • Location: Growing directly on the bark of deciduous trees
  • Appearance: Thin, crusty patches that seem almost painted onto the bark
  • Color: Usually grayish or pale, sometimes with a slightly greenish tint
  • Texture: The telltale black dots (perithecia) scattered across the surface
  • Size: Individual colonies are typically small, just a few inches across

Living Conditions

Wart lichen isn’t picky, but it does have preferences. It thrives in areas with clean air and establishes itself on the bark of various deciduous trees. You’re most likely to spot it in mature landscapes where trees have had time to develop the slightly roughened bark that lichens love.

The Bottom Line

While you can’t add wart lichen to your shopping list at the garden center, you can certainly appreciate it when it shows up naturally. Think of it as a living certificate that your landscape is healthy and your air is clean. The next time you’re wandering around your yard, take a moment to look closely at your trees – you might just discover a whole miniature world of these fascinating organisms living right under your nose!

Remember, the presence of lichens like Pyrenula lucifera is a sign of a balanced, healthy ecosystem. So if you spot these little warts on your trees, give yourself a pat on the back – you’re providing habitat for some pretty amazing life forms.

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 lucifera R.C. Harris - 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