North America Native Plant

Pore Lichen

Botanical name: Pertusaria subamplicata

USDA symbol: PESU15

Habit: lichen

Native status: Native to North America  

Pore Lichen: A Natural Air Quality Indicator in Your Garden Ever noticed those crusty, whitish-gray patches on the bark of your trees? You might be looking at pore lichen (Pertusaria subamplicata), a fascinating organism that’s actually doing your garden a favor just by being there! What Exactly Is Pore Lichen? ...

Pore Lichen: A Natural Air Quality Indicator in Your Garden

Ever noticed those crusty, whitish-gray patches on the bark of your trees? You might be looking at pore lichen (Pertusaria subamplicata), a fascinating organism that’s actually doing your garden a favor just by being there!

What Exactly Is Pore Lichen?

Despite its name suggesting it’s a plant, pore lichen is actually a remarkable partnership between a fungus and algae working together as one organism. This crusty character belongs to the lichen family, making it quite different from the flowers, shrubs, and trees you typically think about when planning your garden.

Pore lichen gets its common name from the tiny pores (called ostioles) that dot its surface, which are the openings to flask-shaped structures where the lichen produces its spores.

Where You’ll Find It

This lichen is native to North America and commonly appears throughout eastern regions of the continent. You’ll typically spot it growing on the bark of deciduous and mixed forest trees, making it a natural resident of wooded areas and mature landscapes.

Is Pore Lichen Beneficial to Your Garden?

Absolutely! While you can’t plant pore lichen like you would a flower or shrub, its presence in your garden is actually a wonderful sign. Here’s why you should be happy to see it:

  • Air quality indicator: Lichens are incredibly sensitive to air pollution, so finding them on your trees means your garden enjoys relatively clean air
  • Ecosystem health: Their presence indicates a balanced, healthy environment
  • No harm to trees: Unlike some organisms, pore lichen doesn’t damage or parasitize the trees it grows on – it just uses the bark as a place to live
  • Natural beauty: These crusty patches add interesting texture and natural character to tree bark

How to Identify Pore Lichen

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

  • Appearance: Forms whitish-gray to pale gray crusty patches that look almost painted onto tree bark
  • Texture: Thick, warty, and crusty rather than leafy or branching
  • Location: Grows directly on the bark of deciduous trees
  • Pores: Look closely and you might see tiny dark dots (the pores) scattered across the surface
  • Size: Can form patches several inches across

Can You Cultivate Pore Lichen?

Here’s where things get interesting – you can’t actually plant or cultivate pore lichen like traditional garden plants. These lichens establish themselves naturally when conditions are right, and they can’t be propagated through typical gardening methods like seeds, cuttings, or divisions.

The best thing you can do to encourage lichen diversity in your garden is to maintain healthy trees, avoid using harsh chemicals near them, and keep air quality as clean as possible. If you’re lucky enough to have pore lichen appear naturally, consider it a badge of honor for your garden’s environmental health!

Should You Be Concerned?

Not at all! Some gardeners worry that lichens might harm their trees, but this is a common misconception. Pore lichen is completely harmless to its host trees and actually serves as a positive indicator of your garden’s ecological well-being.

If you notice pore lichen on your trees, simply appreciate it for what it is – a sign that your garden environment is healthy enough to support these sensitive organisms. There’s no need to remove it, and in fact, doing so would eliminate a beneficial indicator species from your landscape.

So next time you’re wandering through your garden, take a closer look at those crusty patches on your tree bark. You might just be admiring one of nature’s most interesting partnerships at work!

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 subamplicata 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