Types of Lichen That Grow on Rocks

Crustose Lichen

• Crustose lichen is the only plant that will grow on a bare rock. This is accomplished by gathering small amounts of water and then in winter when the water freezes, it cracks the rock surface, providing the lichen with minerals and organic materials. Over time this process forms a tiny bit of soil on the rock. These lichen tend to lay flat on their host, looking much like paint splatters, making them hard to remove. They range in color from black, gray, brown, orange, yellow and green. About 75 percent of all lichen in the world are crustose lichen. When dating stone walls and gravestones, scientists measure the radius of this lichen growth since it grows so slowly and lives for centuries.

Foliose Lichens

• Foliose lichens have small branches and leaf shapes. They are loosely attached to stones and can be easily scrapped off their host surface. Their growth is considered relatively fast for lichens, growing as much as a centimeter in a single year. These bushy looking lichens can be gray, brown, orange or yellow-green.

Desert Varnish

• In the desert Southwest, many boulders and mountain peaks are covered in thin layers of bacteria and lichen nicknamed Desert Varnish. These are considered some of the oldest living plants on Earth.

Pilophoron aciculare

• This rock lichen has thin stems that stand upright and have a black bulbous tip. It thrives in a moist environment and can be found in the coniferous forests of the Northwest.