North America Native Plant

Wart Lichen

Botanical name: Verrucaria phaeothelena

USDA symbol: VEPH3

Habit: lichen

Native status: Native to North America  

Wart Lichen: A Fascinating Natural Phenomenon in Your Garden Have you ever noticed those dark, bumpy patches on rocks in your garden and wondered what they are? You might be looking at Verrucaria phaeothelena, commonly known as wart lichen – a remarkable organism that’s neither plant nor animal, but something ...

Wart Lichen: A Fascinating Natural Phenomenon in Your Garden

Have you ever noticed those dark, bumpy patches on rocks in your garden and wondered what they are? You might be looking at Verrucaria phaeothelena, commonly known as wart lichen – a remarkable organism that’s neither plant nor animal, but something wonderfully unique!

What Exactly is Wart Lichen?

Wart lichen (Verrucaria phaeothelena) is a fascinating example of nature’s partnership at work. Lichens are actually composite organisms made up of a fungus and algae living together in perfect harmony. The fungus provides structure and protection, while the algae produce food through photosynthesis – it’s like having the ultimate roommate arrangement!

This particular species is native to North America and gets its wart nickname from its distinctive bumpy, crusty appearance that forms dark patches on rock surfaces.

Where You’ll Find It

Verrucaria phaeothelena is found throughout North America, typically making its home on various rock surfaces. You might spot it on natural stone outcrops, old stone walls, or even decorative rocks in your landscape.

Identifying Wart Lichen

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

  • Dark, blackish to brownish crusty patches on rocks
  • Warty or bumpy texture that gives it its common name
  • Firmly attached to rock surfaces – you can’t easily peel it off
  • Forms irregular patches that can spread across stone surfaces

Is Wart Lichen Beneficial in Your Garden?

Absolutely! While you can’t plant or cultivate wart lichen (it does its own thing, thank you very much), having it occur naturally in your garden is actually a wonderful sign:

  • Air quality indicator: Lichens are sensitive to air pollution, so their presence suggests you have good air quality
  • Ecosystem health: They contribute to biodiversity and create microhabitats for tiny creatures
  • Natural character: They add authentic, wild character to stone features in your landscape
  • Low maintenance: They require absolutely no care from you – nature’s perfect low-maintenance addition!

Living with Wart Lichen

The beauty of wart lichen is that it’s completely self-sufficient. You don’t need to water it, fertilize it, or worry about pests. It simply exists peacefully on your rocks, slowly growing and contributing to your garden’s ecosystem.

If you have natural stone features, old walls, or rock gardens, consider yourself lucky if wart lichen decides to make itself at home. It’s a sign that your garden is healthy and balanced.

Should You Encourage It?

While you can’t actively plant wart lichen, you can create conditions that might encourage its natural establishment:

  • Maintain good air quality around your property
  • Avoid using harsh chemicals near stone surfaces
  • Let natural stone features age gracefully without power washing
  • Be patient – lichens grow very slowly but are worth the wait

Remember, wart lichen is a native North American species that has been quietly doing its job for countless years. When it appears in your garden, it’s nature’s way of saying you’re doing something right. Embrace these little dark patches as badges of honor for maintaining a healthy, natural garden ecosystem!

Wart Lichen

Classification

Group

Lichen

Kingdom

Fungi - Fungi

Subkingdom
Superdivision
Division

Ascomycota - Sac fungi

Subdivision
Class

Ascomycetes

Subclass
Order

Verrucariales

Family

Verrucariaceae Eschw.

Genus

Verrucaria Schrad. - wart lichen

Species

Verrucaria phaeothelena Th. Fr. - 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