North America Native Plant

Wart Lichen

Botanical name: Porina amygdalina

USDA symbol: POAM15

Habit: lichen

Native status: Native to North America  

Wart Lichen: The Tiny Garden Guest You Never Invited (But Should Welcome) Have you ever noticed small, crusty patches on your tree bark that look like tiny gray warts? Meet Porina amygdalina, commonly known as wart lichen – a fascinating organism that’s probably already living in your garden without you ...

Wart Lichen: The Tiny Garden Guest You Never Invited (But Should Welcome)

Have you ever noticed small, crusty patches on your tree bark that look like tiny gray warts? Meet Porina amygdalina, commonly known as wart lichen – a fascinating organism that’s probably already living in your garden without you even knowing it!

What Exactly Is Wart Lichen?

Before we dive in, let’s clear up a common misconception: wart lichen isn’t actually a plant at all! It’s a lichen, which is a unique partnership between a fungus and algae (or sometimes cyanobacteria) living together in perfect harmony. Think of it as nature’s original roommate situation – both organisms benefit from the arrangement, with the fungus providing structure and protection while the algae produces food through photosynthesis.

Porina amygdalina is native to North America and belongs to a group of lichens that have a distinctly warty, crusty appearance – hence the rather unflattering but accurate common name.

Where You’ll Find This Little Wonder

Wart lichen naturally occurs across North America, particularly in temperate regions where air quality is relatively good. You’ll typically spot it growing on the bark of various trees and occasionally on rocks.

Spotting Wart Lichen in Your Garden

Identifying wart lichen is pretty straightforward once you know what to look for:

  • Small, crusty patches that appear warty or bumpy
  • Gray to brownish-gray coloration
  • Grows directly on tree bark, forming thin crusts
  • Surface texture resembles tiny raised bumps or warts
  • Usually found on the bark of mature trees

Is Wart Lichen Beneficial to Your Garden?

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

Air Quality Indicator: Lichens are incredibly sensitive to air pollution, so finding wart lichen in your garden is actually a good sign – it means your local air quality is decent enough to support these delicate organisms.

Ecosystem Support: While wart lichen doesn’t directly attract pollinators (since it doesn’t flower), it does contribute to the overall biodiversity of your garden ecosystem. Some small insects and microorganisms call lichens home.

No Harm to Trees: Despite growing on tree bark, wart lichen doesn’t harm its host trees. It’s simply using the bark as a surface to live on, not as a food source.

Can You Grow Wart Lichen?

Here’s where things get interesting – you can’t actually plant or cultivate wart lichen like you would a typical garden plant. Lichens are notoriously difficult to grow artificially, and they establish themselves naturally based on environmental conditions.

The best thing you can do to encourage lichens like Porina amygdalina in your garden is to:

  • Maintain good air quality around your property
  • Avoid using harsh chemicals or pesticides near trees
  • Preserve mature trees that provide suitable bark surfaces
  • Be patient – lichens grow very slowly and establish over time

The Bottom Line

Wart lichen might not be the showiest addition to your garden, but it’s definitely one of the most interesting. Think of it as nature’s own little science experiment happening right on your trees. While you can’t plant it yourself, you can appreciate it as a sign of a healthy garden ecosystem and good environmental conditions.

So next time you’re walking around your garden and spot those little gray, warty patches on your trees, give them a friendly nod. They’re doing their part to make your outdoor space a more diverse and fascinating place – no planting required!

Wart Lichen

Classification

Group

Lichen

Kingdom

Fungi - Fungi

Subkingdom
Superdivision
Division

Ascomycota - Sac fungi

Subdivision
Class

Ascomycetes

Subclass
Order

Pyrenulales

Family

Trichotheliaceae Bittner & F. Schill.

Genus

Porina Müll. Arg. - wart lichen

Species

Porina amygdalina Müll. Arg. - wart lichen

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