North America Native Plant

Arthothelium Lichen

Botanical name: Arthothelium subcyrtodes

USDA symbol: ARSU19

Habit: lichen

Native status: Native to North America  

Arthothelium Lichen: A Quiet Garden Companion You Never Planted Have you ever noticed those subtle, pale patches on the bark of trees in your yard and wondered what they are? You might be looking at arthothelium lichen (Arthothelium subcyrtodes), a fascinating organism that’s neither plant nor animal, but something wonderfully ...

Arthothelium Lichen: A Quiet Garden Companion You Never Planted

Have you ever noticed those subtle, pale patches on the bark of trees in your yard and wondered what they are? You might be looking at arthothelium lichen (Arthothelium subcyrtodes), a fascinating organism that’s neither plant nor animal, but something wonderfully in-between.

What Exactly Is Arthothelium Lichen?

Before we dive deeper, let’s clear up a common misconception: lichens aren’t plants! They’re actually a remarkable partnership between fungi and algae (or sometimes cyanobacteria). The fungus provides structure and protection, while the algae produces food through photosynthesis. It’s like nature’s ultimate roommate situation – and it’s been working perfectly for millions of years.

Arthothelium subcyrtodes is what scientists call a crustose lichen, meaning it forms a crust-like layer that’s tightly bonded to its host surface. Think of it as nature’s very own paint job, but one that actually benefits the tree it’s growing on.

Where You’ll Find This Native Beauty

This lichen is native to North America, though the exact details of its geographic range aren’t well-documented in popular literature. Like many lichens, it’s probably more widespread than we realize – these organisms are notoriously understudied despite being everywhere around us.

Spotting Arthothelium Lichen in Your Garden

Identifying arthothelium lichen takes a bit of detective work. Here’s what to look for:

  • Thin, pale patches on tree bark
  • Smooth, crust-like appearance that seems painted on
  • Typically found on the bark of deciduous trees
  • May appear whitish, grayish, or slightly yellowish
  • Lacks the leafy or branched structure of other lichen types

Is It Good for Your Garden?

Absolutely! While you can’t plant or cultivate arthothelium lichen (it does its own thing, thank you very much), 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 their presence suggests your garden has relatively clean air
  • Harmless to trees: Unlike some people think, lichens don’t harm their host trees – they’re just along for the ride
  • Ecosystem support: While we don’t have specific data on wildlife benefits for this species, many lichens provide food and nesting materials for birds and small creatures
  • Natural beauty: These subtle organisms add texture and interest to tree bark, creating natural art in your landscape

The Hands-Off Approach to Lichen Care

Here’s the best part about having arthothelium lichen in your garden: there’s absolutely nothing you need to do! In fact, the best thing you can do is leave it alone. Lichens are incredibly slow-growing and can take years or even decades to establish themselves.

If you want to encourage lichen diversity in your garden:

  • Avoid using harsh chemicals or pesticides near trees
  • Don’t scrub or remove lichens from bark
  • Maintain good air quality around your property
  • Be patient – lichen communities develop very slowly

A Small Marvel Worth Appreciating

While arthothelium lichen might not have the flashy blooms of your favorite flowers or the dramatic presence of a specimen tree, it represents something pretty amazing: a successful partnership that’s been thriving since long before humans started gardening. The next time you’re walking through your garden, take a moment to appreciate these quiet, resilient organisms that have chosen to call your trees home.

Remember, a garden with lichens is a garden with good air quality and a healthy ecosystem. And really, what more could you ask for from a neighbor you never even had to invite over?

Arthothelium Lichen

Classification

Group

Lichen

Kingdom

Fungi - Fungi

Subkingdom
Superdivision
Division

Ascomycota - Sac fungi

Subdivision
Class

Uncertain Ascomycota Class

Subclass
Order

Uncertain Ascomycota Order

Family

Uncertain Ascomycota Family

Genus

Arthothelium A. Massal. - arthothelium lichen

Species

Arthothelium subcyrtodes (Willey) Hasse - arthothelium lichen

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