North America Native Plant

Bacidia Microcarpa

Botanical name: Bacidia microcarpa

USDA symbol: BAMI9

Habit: lichen

Native status: Native to North America  

Synonyms: Mycobilimbia microcarpa (Th. Fr.) W. Brunnbauer (MYMI3)   

Bacidia microcarpa: The Tiny Lichen That’s Actually a Big Deal for Your Garden You might not have heard of Bacidia microcarpa, but there’s a good chance this unassuming little organism is already living in your yard. This native North American lichen might be small and easy to overlook, but it’s ...

Bacidia microcarpa: The Tiny Lichen That’s Actually a Big Deal for Your Garden

You might not have heard of Bacidia microcarpa, but there’s a good chance this unassuming little organism is already living in your yard. This native North American lichen might be small and easy to overlook, but it’s actually doing some pretty amazing things for your garden ecosystem – even if you can’t plant it yourself!

What Exactly Is Bacidia microcarpa?

First things first – Bacidia microcarpa isn’t actually a plant at all! It’s a lichen, which means it’s a fascinating partnership between a fungus and algae (or sometimes cyanobacteria) living together in perfect harmony. You might also see it referred to by its scientific synonym, Mycobilimbia microcarpa, but don’t let the fancy names intimidate you.

This little lichen forms small, crusty patches that you’ll typically find growing on tree bark and occasionally on rocks. It’s what scientists call a crustose lichen, meaning it forms a crust-like layer that’s tightly attached to whatever surface it’s growing on.

Where You’ll Find This Native Beauty

Bacidia microcarpa is a true North American native, making its home across temperate regions of the continent. You’re most likely to spot it in areas with good air quality – which brings us to one of its coolest features.

Why This Lichen Is Actually Great News for Your Garden

Here’s where things get really interesting. While you can’t head to the garden center and pick up a pot of Bacidia microcarpa (because lichens simply can’t be cultivated like regular plants), having it show up naturally in your garden is actually a wonderful sign. This lichen is what’s known as an indicator species – its presence tells you that your local air quality is pretty darn good!

Lichens are incredibly sensitive to air pollution, so when you see Bacidia microcarpa thriving on your trees, you can pat yourself on the back knowing your garden environment is healthy. Plus, these tiny organisms contribute to your garden’s biodiversity in their own quiet way.

How to Identify Bacidia microcarpa

Spotting this lichen takes a bit of patience and a keen eye. Here’s what to look for:

  • Small, crusty patches on tree bark (occasionally on rocks)
  • Typically grayish or whitish in color
  • Forms thin, closely attached crusts that can’t be easily peeled off
  • Often found on the bark of deciduous trees
  • May have tiny, dark spots (these are the fungal reproductive structures)

The Role of Bacidia microcarpa in Your Garden Ecosystem

Even though this lichen doesn’t produce showy flowers or attract butterflies, it’s still pulling its weight in your garden ecosystem. Lichens like Bacidia microcarpa help with nutrient cycling, slowly breaking down the surfaces they grow on and contributing to soil formation over very long periods. They also provide food for some small insects and create microhabitats for tiny creatures you might never notice.

What This Means for Your Gardening Plans

Since you can’t plant or cultivate Bacidia microcarpa, your role as a gardener is more about appreciation and protection. If you notice this lichen in your garden, consider it a compliment to your environmental stewardship! To keep it happy:

  • Avoid using harsh chemicals or pesticides that could affect air quality
  • Be gentle when pruning trees where lichens are growing
  • Maintain good garden practices that support overall ecosystem health
  • Consider it a sign that your garden is providing good habitat

The Bottom Line

While Bacidia microcarpa might not be the showstopper of your garden border, it’s definitely worth getting to know. This little lichen is like having a natural air quality monitor right in your backyard, and its presence indicates that you’re creating a healthy environment for all sorts of life – both big and small. So next time you’re wandering around your garden, take a closer look at those tree trunks. You might just spot this remarkable little organism doing its quiet work!

Bacidia Microcarpa

Classification

Group

Lichen

Kingdom

Fungi - Fungi

Subkingdom
Superdivision
Division

Ascomycota - Sac fungi

Subdivision
Class

Ascomycetes

Subclass
Order

Lecanorales

Family

Bacidiaceae Walt. Watson

Genus

Bacidia De Not. - dotted lichen

Species

Bacidia microcarpa (Th. Fr.) Lettau

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