North America Native Plant

Dot Lichen

Botanical name: Arthonia atrata

USDA symbol: ARAT7

Habit: lichen

Native status: Native to North America  

Dot Lichen: The Tiny Garden Guest You Never Knew You Had If you’ve ever taken a close look at the bark of trees in your garden, you might have noticed tiny dark spots scattered across the surface like nature’s own polka dots. Meet the dot lichen (Arthonia atrata), a fascinating ...

Dot Lichen: The Tiny Garden Guest You Never Knew You Had

If you’ve ever taken a close look at the bark of trees in your garden, you might have noticed tiny dark spots scattered across the surface like nature’s own polka dots. Meet the dot lichen (Arthonia atrata), a fascinating little organism that’s probably been quietly living in your landscape without you even realizing it!

What Exactly Is Dot Lichen?

Despite its name suggesting it’s a plant, dot lichen is actually a unique partnership between a fungus and algae working together in perfect harmony. This remarkable collaboration creates those small, dark circular or oval spots you see on tree bark. Think of it as nature’s version of roommates who actually get along – the fungus provides shelter and minerals, while the algae produces food through photosynthesis.

Where You’ll Find This Native Beauty

Dot lichen is native to North America and can be found across the continent wherever suitable host trees grow. It’s not picky about its accommodations – you’ll spot it on various tree species, from oaks to maples to birches.

Identifying Dot Lichen in Your Garden

Spotting dot lichen is like playing nature’s version of connect-the-dots:

  • Look for small, dark brown to black circular spots on tree bark
  • The spots are typically 1-3mm in diameter
  • They appear flat against the bark surface
  • You’ll often find multiple spots clustered together
  • The edges are usually well-defined and smooth

Is Dot Lichen Beneficial for Your Garden?

Absolutely! While you might not have invited dot lichen to your garden party, it’s actually a wonderful guest to have around:

  • Air quality indicator: Lichens are sensitive to air pollution, so their presence suggests you have relatively clean air in your garden
  • Ecosystem health: They’re part of a healthy, functioning ecosystem
  • Minimal impact: Unlike some organisms, they don’t harm their host trees
  • Natural beauty: They add subtle texture and visual interest to bark

Can You Grow Dot Lichen?

Here’s where things get interesting – you can’t actually plant or grow dot lichen like you would a flower or shrub. These little partners establish themselves naturally when conditions are right. They’re like that friend who shows up when the vibe is perfect but can’t be convinced to come to a party they’re not feeling.

The best thing you can do to encourage lichens in your garden is to maintain a healthy environment with good air quality and avoid using harsh chemicals near your trees.

Living Harmoniously with Dot Lichen

If you discover dot lichen in your garden, consider yourself lucky! There’s no need to remove it or worry about it harming your trees. Simply appreciate this tiny example of nature’s cooperation and the role it plays in your garden’s ecosystem.

Next time you’re walking through your garden, take a moment to look closely at your tree bark. You might be surprised by the intricate world of lichens that’s been there all along, quietly contributing to the natural beauty and health of your outdoor space.

Dot Lichen

Classification

Group

Lichen

Kingdom

Fungi - Fungi

Subkingdom
Superdivision
Division

Ascomycota - Sac fungi

Subdivision
Class

Ascomycetes

Subclass
Order

Arthoniales

Family

Arthoniaceae Rchb.

Genus

Arthonia Ach. - dot lichen

Species

Arthonia atrata (Fée) Müll. Arg. - dot lichen

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