North America Native Plant

Map Lichen

Botanical name: Rhizocarpon saanaense

USDA symbol: RHSA5

Habit: lichen

Native status: Native to North America  

Synonyms: Rhizocarpon sublucidum Rasanen (RHSU5)   

Map Lichen: A Hardy Rock-Dwelling Wonder You Can’t Plant (But Should Appreciate!) Have you ever noticed those grayish, crusty patches decorating rocks in wild places and wondered what they were? Meet the map lichen, scientifically known as Rhizocarpon saanaense – a fascinating organism that’s neither plant nor animal, but something ...

Map Lichen: A Hardy Rock-Dwelling Wonder You Can’t Plant (But Should Appreciate!)

Have you ever noticed those grayish, crusty patches decorating rocks in wild places and wondered what they were? Meet the map lichen, scientifically known as Rhizocarpon saanaense – a fascinating organism that’s neither plant nor animal, but something wonderfully unique.

What Exactly Is Map Lichen?

Here’s where things get interesting: map lichen isn’t actually a plant at all! It’s a lichen – a remarkable partnership between a fungus and an algae that work together to create something entirely new. Think of it as nature’s ultimate roommate situation, where both partners benefit from the arrangement.

This particular species belongs to the crustose lichen family, meaning it forms a crust-like layer that’s tightly bonded to rock surfaces. The name map lichen comes from the way these lichens can create intricate, map-like patterns across stone surfaces.

Where Does Map Lichen Call Home?

Map lichen is a true North American native, thriving in the harshest conditions you can imagine – primarily in arctic and subarctic regions. You’ll find this tough little organism clinging to rocks in some of the coldest, most challenging environments on the continent.

Can You Grow Map Lichen in Your Garden?

Here’s the short answer: nope! And here’s why that’s actually perfectly fine:

  • Lichens like Rhizocarpon saanaense can’t be cultivated or planted like traditional garden plants
  • They require very specific partnerships between fungi and algae that develop naturally over time
  • They need extremely cold conditions and specific rock substrates to survive
  • They grow incredibly slowly – we’re talking millimeters per year!

How to Identify Map Lichen

If you’re hiking in northern regions or mountainous areas, keep an eye out for these characteristics:

  • Grayish, crusty patches tightly adhered to rock surfaces
  • Irregular, map-like patterns and boundaries
  • Extremely hardy appearance, often found in exposed, harsh locations
  • No visible leaves, stems, or traditional plant structures

The Garden Connection: Why Map Lichen Matters

While you can’t invite map lichen into your garden, understanding these remarkable organisms can deepen your appreciation for nature’s complexity. Lichens like Rhizocarpon saanaense are:

  • Excellent indicators of air quality – they’re sensitive to pollution
  • Pioneer species that help break down rock and create soil over geological time
  • Food sources for wildlife in harsh environments where little else can survive
  • Living examples of successful symbiosis in nature

Appreciating What You Can’t Control

Sometimes the most beautiful aspects of nature are the ones we can observe and appreciate rather than cultivate. Map lichen reminds us that there’s incredible beauty and resilience in the wild spaces beyond our garden gates. The next time you’re exploring rocky, northern landscapes, take a moment to appreciate these ancient partnerships quietly doing their work, one tiny bit of rock at a time.

While you might not be able to grow map lichen in your backyard, you can certainly grow an appreciation for the incredible diversity and resilience of native North American organisms – even the ones that paint slow-motion masterpieces on stone!

Map Lichen

Classification

Group

Lichen

Kingdom

Fungi - Fungi

Subkingdom
Superdivision
Division

Ascomycota - Sac fungi

Subdivision
Class

Ascomycetes

Subclass
Order

Lecanorales

Family

Rhizocarpaceae M. Choisy ex Hafellner

Genus

Rhizocarpon Ramond ex DC. - map lichen

Species

Rhizocarpon saanaense Rasanen - map lichen

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