North America Native Plant

Pore Lichen

Botanical name: Pertusaria subdactylina

USDA symbol: PESU16

Habit: lichen

Native status: Native to North America  

Discovering Pore Lichen: A Garden’s Natural Air Quality Indicator Have you ever noticed those crusty, grayish patches on the bark of your mature trees and wondered what they were? Meet the pore lichen (Pertusaria subdactylina), a fascinating organism that’s actually doing your garden a favor by serving as a living ...

Discovering Pore Lichen: A Garden’s Natural Air Quality Indicator

Have you ever noticed those crusty, grayish patches on the bark of your mature trees and wondered what they were? Meet the pore lichen (Pertusaria subdactylina), a fascinating organism that’s actually doing your garden a favor by serving as a living air quality monitor!

What Exactly Is Pore Lichen?

Pore lichen isn’t a plant at all – it’s actually a unique partnership between a fungus and algae working together as one organism. This native North American species gets its common name from the distinctive pore-like openings (called ostioles) that dot its surface, giving it a somewhat pockmarked appearance that’s actually quite charming once you know what to look for.

Where You’ll Find Pore Lichen

This lichen is native to eastern North America, where it naturally colonizes the bark of deciduous trees. You’re most likely to spot it in areas with good air quality, as lichens are notoriously sensitive to air pollution.

Identifying Pore Lichen in Your Garden

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

  • Forms crusty, flat patches on tree bark
  • Pale gray to whitish color, sometimes with a slight greenish tinge
  • Distinctive small, dark pore-like openings scattered across the surface
  • Typically found on the bark of mature deciduous trees
  • Patches can range from small spots to larger, irregular shapes

Is Pore Lichen Beneficial for Your Garden?

Absolutely! While you can’t plant or cultivate pore lichen (it appears naturally when conditions are right), its presence is actually a wonderful sign for your garden ecosystem:

  • Air quality indicator: The presence of pore lichen tells you that your garden has clean, unpolluted air
  • Harmless to trees: Despite growing on bark, lichens don’t harm their host trees – they’re just using the bark as a surface to live on
  • Adds natural character: These organisms contribute to the authentic, wild appearance of mature woodland gardens
  • Part of the ecosystem: While not a major food source, some insects and small creatures may graze on lichens

Creating Conditions for Natural Lichen Growth

Since you can’t plant pore lichen, the best thing you can do is create an environment where it might naturally appear:

  • Maintain good air quality around your property
  • Allow mature trees to age naturally without excessive cleaning or bark removal
  • Avoid using harsh chemicals or pesticides near trees
  • Keep trees healthy through proper watering and care
  • Be patient – lichens grow very slowly and may take years to establish

What About Care and Maintenance?

Here’s the best part about pore lichen – it requires absolutely no care from you! In fact, the best thing you can do is simply leave it alone. Avoid scrubbing or removing lichens from tree bark, as they’re not causing any harm and their presence indicates a healthy environment.

The Bottom Line

While pore lichen might not be the showstopper flowering plant you can add to your shopping list, discovering it growing naturally in your garden is like receiving a gold star for environmental stewardship. It’s nature’s way of telling you that you’re providing a clean, healthy habitat for a diverse range of organisms. So the next time you spot those distinctive pore-covered patches on your trees, take a moment to appreciate this remarkable partnership of fungus and algae that’s quietly monitoring your garden’s air quality!

Pore Lichen

Classification

Group

Lichen

Kingdom

Fungi - Fungi

Subkingdom
Superdivision
Division

Ascomycota - Sac fungi

Subdivision
Class

Ascomycetes

Subclass
Order

Lecanorales

Family

Pertusariaceae Körb.

Genus

Pertusaria DC. - pore lichen

Species

Pertusaria subdactylina Nyl. - pore lichen

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