This is a common and easy to identify lichen, found throughout the northeastern United States and into Canada. I encountered it while visiting Carter Caves, Kentucky.
The little red fruiting structure of the lichens resemble the red hats worn by invading British troops during the American Revolutionary War; they give this lichen its common name.
This composite organism is a mutualistic association between a fungus and green alga. In theory, the fungus receives sugars from the photosynthetic activities of the alga, while the alga receives some minerals and a safe place to live from the fungus.
British Soldier Lichen prefers to grow on rotting wood and these examples were on decayinging wooden posts. It also is often found at the base of old tree stumps.
These are among the most colorful of all lichens. Their bright red caps don’t form until the organism is at least 4 years old. They are extremely slow growing, only gaining 1-2 millimeters a year.
“Back in the day” British Soldier Lichens were used to create pink dye for wool. These days it is often a colorful addition to terrariums.