North America Native Plant

Orange Lichen

Botanical name: Caloplaca atroabla

USDA symbol: CAAT17

Habit: lichen

Native status: Native to North America  

Orange Lichen: A Colorful Natural Wonder You Can’t Plant (But Should Appreciate!) Ever noticed small patches of bright orange or yellow-orange crusty stuff on rocks and wondered what it was? You might be looking at orange lichen, scientifically known as Caloplaca atroabla! This fascinating organism isn’t actually a plant at ...

Orange Lichen: A Colorful Natural Wonder You Can’t Plant (But Should Appreciate!)

Ever noticed small patches of bright orange or yellow-orange crusty stuff on rocks and wondered what it was? You might be looking at orange lichen, scientifically known as Caloplaca atroabla! This fascinating organism isn’t actually a plant at all – it’s something much more interesting.

What Exactly Is Orange Lichen?

Orange lichen is what scientists call a crustose lichen, which means it forms a crusty, flat layer that’s tightly bonded to whatever surface it’s growing on. But here’s the really cool part: lichens aren’t plants, fungi, or animals. They’re actually a partnership between fungi and algae working together as one organism! Think of it as nature’s ultimate roommate situation.

This particular species, Caloplaca atroabla, is native to North America and creates those eye-catching orange to yellow-orange patches you might spot on rocks, stone walls, or other hard surfaces.

Where Can You Find Orange Lichen?

Orange lichen naturally occurs across North America, with a particular presence in western regions. You’re most likely to encounter it growing on various types of rock surfaces, from natural stone outcroppings to old stone walls and even concrete surfaces.

Is Orange Lichen Beneficial for Your Garden?

While you can’t plant or cultivate orange lichen (more on that in a moment), having it show up naturally in your garden is actually a good sign! Here’s why:

  • It indicates good air quality – lichens are sensitive to pollution
  • It adds natural color and texture to stone features
  • It’s completely harmless to other plants and structures
  • It represents a healthy ecosystem at work

How to Identify Orange Lichen

Spotting orange lichen is pretty straightforward once you know what to look for:

  • Bright orange to yellow-orange coloring
  • Crusty, flat appearance that looks painted onto the surface
  • Grows exclusively on hard surfaces like rocks, concrete, or stone
  • Forms irregular patches or circular colonies
  • Feels rough and crusty to the touch

Why You Can’t (And Shouldn’t Try to) Grow Orange Lichen

Here’s where orange lichen differs dramatically from traditional garden plants: you simply cannot cultivate, plant, or grow it intentionally. Lichens have incredibly specific requirements that are nearly impossible to replicate artificially. They need:

  • Exact combinations of fungi and algae
  • Specific environmental conditions
  • The right type of substrate (surface to grow on)
  • Particular air quality and moisture levels

Attempting to transplant lichen typically results in its death, so it’s best to simply appreciate it where it naturally occurs.

Caring for Natural Orange Lichen

While you can’t plant orange lichen, you can help preserve any that naturally appears in your landscape:

  • Avoid using harsh chemicals or pressure washing on surfaces where it grows
  • Don’t scrub or scrape it off – it’s not harmful and adds character
  • Maintain good air quality around your property
  • Avoid disturbing the rocks or surfaces where it’s established

The Bottom Line

Orange lichen might not be something you can add to your shopping list at the garden center, but it’s definitely something worth appreciating when it shows up naturally. Consider it a free, living decoration that tells you your local environment is healthy enough to support these fascinating organisms. So the next time you spot those bright orange crusty patches on a rock wall or stone feature, take a moment to marvel at one of nature’s most successful partnerships in action!

Orange Lichen

Classification

Group

Lichen

Kingdom

Fungi - Fungi

Subkingdom
Superdivision
Division

Ascomycota - Sac fungi

Subdivision
Class

Ascomycetes

Subclass
Order

Teloschistales

Family

Teloschistaceae Zahlbr.

Genus

Caloplaca Th. Fr. - orange lichen

Species

Caloplaca atroabla (Tuck.) Zahlbr. - orange lichen

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