Lichens make subtle, essential contribution

Now that the fall color has gone, many of the more subtle aspects of nature become visible. With the leaves off the trees, bark color and texture are much more prominent. Grasses have taken on dozens of shades of tan and gold. Splashes of color are out there in the form of fruits and berries left handing on the shrubs and trees or from bright green lichen patches on trees and rocks.

We’ve all seen lichens. They are the odd flaky crusts and moss-like wisps of growth found attached to the bark of older branches and tree trunks, downed trees, old fence posts and even bare rocks. They come in a wide range of colors from gray and white, chartreuse greens and even rusts and yellows.

Lichens have been around for billions of years and are often the first plant to colonize a new area. Lichens are made up of a union of specific fungi and algae and sometimes photosynthesizing bacteria. They form when a fungal spore finds a host and its thread-like hypha captures algae particles. The fungus then grows into and around the algae forming a completely new plant. Once combined, the fungus and the algae sustain each other; the fungus soaks up water and nutrients from the environment while the algae provide nutrients through photosynthesis. The fungus also provides the shape and structure for the lichen.

Crustose lichens form thin patches with indistinct edges. They adhere tightly to their host and can be hard to see. These lichens are commonly found on bare rock surfaces. Foliose lichens form flat, thin scaly pads with distinct wavy edges that can be pulled up. Fruticose lichens are shrubby bodies that rise off the surface and often look fuzzy or wispy. When they grow large, some forms will hang down from tree branches like a beard.

Lichens are important ecologically because they are often the first plant to colonize a surface and begin the decomposition process. When they attach themselves to bare rock, the water retained by the lichen freezes and thaws breaking away tiny fragments of rock. The fragments begin to build up a thin soil that can eventually support other life. On woody material, the lichen slowly breaks down the outer surface and return nutrients to the soil. Lichens are also able to take nitrogen from the air and return it to the soil where other plants can use it. The presence of lichens also means the air pollution is low as they are very sensitive to airborne contaminates.

For these reasons, gardeners should just leave lichens they find growing on trees and shrubs alone. They are an important part of the ecology of the garden. There is also no way to remove or prevent their growth.

Culturally, lichens have been used worldwide as food, dyes, medicines, poisons and even as an embalming herb by early Egyptians. Edible lichens were often ground and added to other foods. As a dye plant, different lichens could provide a wide range of colors from purples to yellow to reds.