North America Native Plant

Physconia Thomsonii

Botanical name: Physconia thomsonii

USDA symbol: PHTH5

Habit: lichen

Native status: Native to North America  

Physconia thomsonii: A Fascinating North American Lichen Worth Knowing If you’ve ever noticed gray-green, leafy patches growing on tree bark in your yard, you might have encountered Physconia thomsonii, a fascinating lichen species native to North America. While you can’t exactly plant this intriguing organism in your garden, understanding what ...

Physconia thomsonii: A Fascinating North American Lichen Worth Knowing

If you’ve ever noticed gray-green, leafy patches growing on tree bark in your yard, you might have encountered Physconia thomsonii, a fascinating lichen species native to North America. While you can’t exactly plant this intriguing organism in your garden, understanding what it is and recognizing its presence can add a whole new dimension to your appreciation of the natural world around you.

What Exactly Is Physconia thomsonii?

Physconia thomsonii is what scientists call a foliose lichen – think of it as nature’s partnership between a fungus and algae working together in perfect harmony. This collaborative organism appears as broad, overlapping lobes that create a somewhat leafy appearance, though it’s definitely not a plant in the traditional sense. The partnership is pretty clever: the fungus provides structure and protection, while the algae handles the photosynthesis duties.

Where You’ll Find This Lichen

This lichen calls North America home, thriving in temperate regions across the continent. You’re most likely to spot Physconia thomsonii growing on the bark of deciduous trees, though it occasionally makes itself comfortable on rocks and other surfaces. It particularly enjoys areas with good air quality, making it somewhat of a natural air pollution detector.

Identifying Physconia thomsonii

Spotting this lichen is like playing nature’s version of I Spy. Here’s what to look for:

  • Gray-green coloration that might appear slightly bluish in certain light
  • Broad, overlapping lobes that create a leafy, layered appearance
  • Typically found on tree bark, especially on the north side or in shaded areas
  • Smooth to slightly wrinkled surface texture
  • Size can vary from small patches to more extensive colonies

Is It Beneficial to Have in Your Garden?

While you can’t cultivate Physconia thomsonii like you would a tomato plant, having it naturally occur in your garden space is actually a wonderful sign. This lichen serves as a living indicator of good air quality – it’s quite sensitive to pollution and won’t thrive in areas with poor air conditions. Think of it as nature’s way of giving your garden a clean air certificate!

Additionally, lichens like Physconia thomsonii contribute to the overall biodiversity of your outdoor space. They provide microhabitats for tiny insects and other small creatures, and some birds may use bits of lichen for nesting material. They’re also fascinating conversation starters when you’re showing visitors around your garden.

What You Can Do to Support Lichens

Since you can’t plant lichens, the best thing you can do is create conditions that allow them to thrive naturally:

  • Maintain good air quality around your property by avoiding excessive use of chemicals
  • Preserve mature trees, as they provide the bark substrate lichens need
  • Avoid scrubbing or removing lichens from tree bark – they’re not harming the tree
  • Keep an eye out for these fascinating organisms and appreciate their presence

The Bottom Line

Physconia thomsonii might not be something you can add to your shopping list at the garden center, but recognizing and appreciating this native lichen can enhance your connection to the natural ecosystem in your own backyard. Consider yourself lucky if you spot this air-quality indicator growing naturally on your trees – it’s a sign that your local environment is healthy and thriving. Who knew that something so small and unassuming could tell such a big story about the world around us?

Physconia Thomsonii

Classification

Group

Lichen

Kingdom

Fungi - Fungi

Subkingdom
Superdivision
Division

Ascomycota - Sac fungi

Subdivision
Class

Ascomycetes

Subclass
Order

Lecanorales

Family

Physciaceae Zahlbr.

Genus

Physconia Poelt - frosted lichen

Species

Physconia thomsonii Essl.

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