North America Native Plant

Pyrenula Caryae

Botanical name: Pyrenula caryae

USDA symbol: PYCA9

Habit: lichen

Native status: Native to North America  

Pyrenula caryae: The Hickory Tree’s Crusty Companion If you’ve ever taken a close look at the bark of mature trees in your garden or local forest, you might have noticed some interesting crusty patches that look almost painted on. Meet Pyrenula caryae, a fascinating lichen that calls the bark of ...

Pyrenula caryae: The Hickory Tree’s Crusty Companion

If you’ve ever taken a close look at the bark of mature trees in your garden or local forest, you might have noticed some interesting crusty patches that look almost painted on. Meet Pyrenula caryae, a fascinating lichen that calls the bark of various trees home, particularly hickories and other hardwoods across North America.

What Exactly Is Pyrenula caryae?

Before we dive deeper, let’s clear up what we’re dealing with here. Pyrenula caryae isn’t a plant in the traditional sense – it’s a lichen! Lichens are remarkable organisms that are actually a partnership between fungi and algae (or sometimes cyanobacteria). Think of them as nature’s ultimate roommates, working together to create something neither could achieve alone.

This particular lichen forms thin, crusty patches on tree bark that can appear grayish-white to pale in color. It’s what scientists call a crustose lichen, meaning it grows flat against its host surface like a living paint job.

Where You’ll Find This Bark-Dwelling Beauty

Pyrenula caryae is native to North America and tends to prefer the eastern regions of the continent. You’re most likely to spot it in deciduous forests where it makes itself at home on the bark of hickory trees, oaks, and other hardwoods.

Is It Good for Your Garden?

Here’s the cool thing about finding Pyrenula caryae in your garden – it’s actually a sign that you’re doing something right! Lichens like this one are sensitive to air pollution, so their presence indicates good air quality in your area. They’re basically nature’s air quality monitors.

While you can’t plant or cultivate lichens like traditional garden plants, having them naturally appear in your garden ecosystem is definitely a win. They:

  • Indicate healthy environmental conditions
  • Add subtle texture and interest to tree bark
  • Contribute to the overall biodiversity of your garden
  • Provide microscopic habitat for tiny creatures

How to Identify Pyrenula caryae

Spotting this lichen takes a bit of detective work, but it’s totally doable! Here’s what to look for:

  • Thin, crusty patches on tree bark that look almost like they’ve been painted on
  • Grayish-white to pale coloration
  • Smooth, relatively flat appearance against the bark surface
  • Most commonly found on hickory trees, but also on other hardwood species
  • Typically appears in patches that can range from small spots to larger areas

The best time to look for lichens is after rain when they’re more vibrant and easier to spot against the darker, wet bark.

Creating Lichen-Friendly Conditions

While you can’t plant Pyrenula caryae like you would a flower or shrub, you can certainly encourage lichens to make themselves at home in your garden:

  • Maintain mature trees, especially native hardwoods like hickories and oaks
  • Avoid using harsh chemicals or pesticides that could harm these sensitive organisms
  • Keep air quality good by choosing eco-friendly garden practices
  • Be patient – lichens grow very slowly and establish naturally over time

The Bottom Line

Pyrenula caryae might not be the showiest addition to your garden, but it’s definitely one of the most interesting! Think of it as a living certificate of your garden’s environmental health. You can’t buy it at the nursery or plant it yourself, but if you’re lucky enough to have it show up naturally on your trees, consider it a badge of honor.

Next time you’re wandering around your garden or local woods, take a moment to appreciate these tiny marvels. They’re proof that some of nature’s most fascinating partnerships happen right under our noses – or should we say, right on our trees!

Pyrenula Caryae

Classification

Group

Lichen

Kingdom

Fungi - Fungi

Subkingdom
Superdivision
Division

Ascomycota - Sac fungi

Subdivision
Class

Ascomycetes

Subclass
Order

Pyrenulales

Family

Pyrenulaceae Rabenh.

Genus

Pyrenula Ach. - wart lichen

Species

Pyrenula caryae 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