North America Native Plant

Thelotrema Monospermum

Botanical name: Thelotrema monospermum

USDA symbol: THMO11

Habit: lichen

Native status: Native to North America  

Synonyms: Leptotrema lepadodes (Tuck.) Zahlbr. (LELE24)  ⚘  Leptotrema monosporum (Nyl.) Müll. Arg. (LEMO14)  ⚘  Thelotrema monosporum Nyl. (THMO9)   

Thelotrema monospermum: The Quiet Guardian of Your Garden Trees Ever noticed those subtle, whitish patches decorating the bark of your mature trees? You might be looking at Thelotrema monospermum, a fascinating lichen that’s been quietly doing important work in North American forests for centuries. While you can’t exactly plant this ...

Thelotrema monospermum: The Quiet Guardian of Your Garden Trees

Ever noticed those subtle, whitish patches decorating the bark of your mature trees? You might be looking at Thelotrema monospermum, a fascinating lichen that’s been quietly doing important work in North American forests for centuries. While you can’t exactly plant this little ecosystem engineer, understanding what it is and why it matters can give you valuable insights into the health of your landscape.

What Exactly Is Thelotrema monospermum?

Let’s clear up any confusion right away – Thelotrema monospermum isn’t a plant you can pick up at your local nursery. It’s actually a lichen, which means it’s a remarkable partnership between a fungus and an algae (or sometimes a cyanobacterium) living together in perfect harmony. Think of it as nature’s original collaboration project!

This particular lichen forms thin, crusty patches on tree bark, creating what scientists call a crustose growth form. You might also encounter it under its former scientific names, including Leptotrema lepadodes and Thelotrema monosporum, but don’t let the name changes confuse you – it’s the same helpful organism.

Where You’ll Find This Native Lichen

Thelotrema monospermum is a proud native of North America, particularly thriving in the eastern regions where deciduous forests create the perfect conditions for its growth. You’ll typically spot it on the bark of mature hardwood trees in areas with good humidity and relatively clean air.

Why This Lichen Is Actually Great News for Your Garden

Here’s where things get exciting – finding Thelotrema monospermum in your landscape is like getting a gold star for environmental stewardship! This lichen serves as a natural air quality monitor. Its presence suggests that your local air is relatively clean and free from excessive pollution, since lichens are notoriously sensitive to air contaminants.

While it won’t attract pollinators like flowering plants do (lichens don’t produce flowers), it does contribute to the broader ecosystem in subtle but important ways:

  • Provides microhabitat for tiny insects and other small creatures
  • Contributes to nutrient cycling in forest ecosystems
  • Indicates healthy, mature tree communities
  • Adds to the natural biodiversity of your landscape

How to Identify Thelotrema monospermum

Spotting this lichen requires a bit of detective work, but it’s totally doable! Look for thin, whitish to pale gray crusty patches on the bark of deciduous trees. The surface might appear slightly bumpy or textured, and you’ll often need to look closely to distinguish it from other similar lichens.

The key identifying features include:

  • Crustose (crusty) growth form that adheres tightly to bark
  • Whitish to light gray coloration
  • Preference for deciduous tree bark
  • Presence in areas with good air quality

Can You Encourage This Lichen in Your Landscape?

While you can’t plant Thelotrema monospermum like you would a shrub or flower, you can certainly create conditions that welcome it and other beneficial lichens to your property. The secret is maintaining a healthy, mature tree canopy and minimizing pollution sources.

Here’s how to create a lichen-friendly environment:

  • Preserve mature deciduous trees, especially oaks, maples, and other hardwoods
  • Avoid using harsh chemicals or pesticides that could affect air quality
  • Maintain good humidity levels by preserving natural vegetation
  • Be patient – lichens grow slowly and establish naturally over time

The Bottom Line on This Bark-Dwelling Beauty

Thelotrema monospermum might not be the showstopper that catches every visitor’s eye, but it’s definitely one of those quiet heroes that makes your landscape ecosystem more complete and healthy. Think of it as nature’s way of giving your property a seal of approval for good environmental stewardship.

Rather than trying to cultivate this lichen directly, focus on creating the kind of mature, diverse landscape where it can naturally establish itself. When you spot those subtle crusty patches on your trees, take a moment to appreciate the complex partnerships and environmental indicators they represent. After all, having Thelotrema monospermum in your landscape means you’re doing something very right!

Thelotrema Monospermum

Classification

Group

Lichen

Kingdom

Fungi - Fungi

Subkingdom
Superdivision
Division

Ascomycota - Sac fungi

Subdivision
Class

Ascomycetes

Subclass
Order

Graphidales

Family

Thelotremataceae Stizenb.

Genus

Thelotrema Ach. - barnacle lichen

Species

Thelotrema monospermum R.C. Harris

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