North America Native Plant

Leptogium Subaridum

Botanical name: Leptogium subaridum

USDA symbol: LESU42

Habit: lichen

Native status: Native to North America  

Discovering Leptogium subaridum: A North American Lichen Worth Knowing If you’ve ever noticed crusty, grayish patches growing on tree bark or rocks in your garden, you might have encountered Leptogium subaridum without even knowing it! This fascinating organism isn’t actually a plant at all – it’s a lichen, which makes ...

Discovering Leptogium subaridum: A North American Lichen Worth Knowing

If you’ve ever noticed crusty, grayish patches growing on tree bark or rocks in your garden, you might have encountered Leptogium subaridum without even knowing it! This fascinating organism isn’t actually a plant at all – it’s a lichen, which makes it quite special in the world of garden biodiversity.

What Exactly Is Leptogium subaridum?

Leptogium subaridum is a native North American lichen that belongs to a remarkable group of organisms. Lichens are actually a partnership between fungi and algae (or sometimes cyanobacteria), working together in perfect harmony. Think of it as nature’s ultimate roommate situation – the fungus provides structure and protection, while the algae produce food through photosynthesis.

This particular lichen species can be found across various regions of North America, quietly doing its important work in forests, parks, and even urban environments.

How to Spot This Garden Visitor

Identifying Leptogium subaridum is easier than you might think once you know what to look for:

  • Appearance: Forms crusty, patch-like growths that are typically gray to brownish in color
  • Texture: Has a somewhat rough, crusty surface that might remind you of dried paint
  • Location: You’ll find it growing on tree bark, rocks, and sometimes soil
  • Size: Individual patches can vary from small spots to larger colonies several inches across
  • Fruiting bodies: May have small, dark spots or bumps which are its reproductive structures

Is It Beneficial to Have in Your Garden?

Absolutely! While you can’t plant or cultivate Leptogium subaridum (lichens establish themselves naturally), having it appear in your garden is actually a good sign. Here’s why this little organism is worth celebrating:

  • Air quality indicator: Lichens are sensitive to air pollution, so their presence suggests you have relatively clean air
  • Ecosystem support: They provide food and habitat for tiny insects and other small creatures
  • Natural beauty: Adds interesting textures and subtle colors to tree bark and rock surfaces
  • No harm to plants: Unlike some growths, lichens don’t damage the trees or surfaces they grow on
  • Educational value: Great for teaching kids about symbiosis and different life forms

Creating Lichen-Friendly Conditions

While you can’t plant lichens, you can encourage their natural development by maintaining a healthy, low-pollution environment:

  • Avoid using harsh chemicals or pesticides near trees and rocks
  • Maintain good air circulation in your garden
  • Preserve mature trees with textured bark
  • Keep some natural stone or rock features in your landscape
  • Be patient – lichens grow very slowly and establish themselves over time

The Bottom Line

Leptogium subaridum might not be the showiest addition to your garden, but it’s certainly one of the most interesting from a biological perspective. If you spot these crusty gray patches in your outdoor spaces, take a moment to appreciate this remarkable partnership between fungi and algae that’s been working successfully for millions of years.

Rather than trying to remove lichens (which isn’t necessary anyway), embrace them as a sign of a healthy, balanced ecosystem. They’re proof that your garden is supporting biodiversity in ways you might never have imagined – right down to the microscopic level!

Leptogium Subaridum

Classification

Group

Lichen

Kingdom

Fungi - Fungi

Subkingdom
Superdivision
Division

Ascomycota - Sac fungi

Subdivision
Class

Ascomycetes

Subclass
Order

Lecanorales

Family

Collemataceae Zenker

Genus

Leptogium (Ach.) A. Gray - skin lichen

Species

Leptogium subaridum P.M. Jørg. & Goward

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