What’s not to like about lichen?

By Jim Janke | Apr 28, 2014

by Jane Falkenstein

One of those oddities we notice on our trees and woody shrubs is the presence of lichen (“li’-ken”).  Lichen is an opportunist, the combination of two life forms: fungus and algae, usually the blue/green kind. Elementary students learn: “Alice Algae met Freddie Fungus and they got to ‘lichen’ each other.” When dealing with lichen on your plants and trees, it helps to remember this relationship and to note that this pairing is no threat to the flora they inhabit. While lichen is easiest to spot in the winter months, it’s pretty easy to spot it throughout the year.  A tree that is not doing well or a shrub that’s bare even in summer is obvious, as are tree limbs covered with lichen and not much else. If you look closely, you’ll probably see lichen flourishing to one degree or another.

Lichen establishes itself where it gets sunlight on the algal part of the plant. Sparse canopies and plants that either lack leaves to block sunlight or produce very thin leaves are attractive to lichen.  Pruning can produce a thicker canopy the next growing season. The lichen will most likely lessen because it’s not getting the sun it needs to photosynthesize its food.  The fungal part of lichen, for which the lichen is named, is the base for the plant and provides support and soaks up the moisture the algal component needs. It does not affect the bark of its host plant at all and can, depending upon your outlook on such things, add texture and visual interest to its host plant or tree.

Lichen is often grayish-green and has several stages in its life cycle. Like other members of the plant kingdom, when it has a fruiting body it’s more interesting, sometimes to the point of looking oddly out-of-control.  Some lichens are crusty structures, firmly attached to the bark of the tree. Others look like tiny gray, blue, yellow, brown, or even red leafy forms. The hair-like, fruiting body is often mistaken for sphagnum moss, which is not lichen at all though they often grow next to each other in some climates.

The point to consider when you see lichen is not whether it’s attacking your plants and making them sick, but what the culture around those plants or trees might be. Poor soil, lack of water, or need for proper pruning are often what’s contributing to the opportunistic lichen taking up housekeeping. For instance, it’s not uncommon to see trees and shrubs around malls and businesses that are covered in lichen, from top to bottom.  Such sad specimens could have benefited from a soil sample and proper soil amendment when necessary, good mulch, and timely watering.  Just as sadly, a lot of folks still believe that good care ends at planting, not realizing that it’s just the beginning.

Lichen plays a positive role in the environment as food for deer, hummingbirds, squirrels, and frogs, depending on the fungus in partnership with algae. Lichens are great bio-indicators for air quality because their tiny bodies act as air filters. Though they are very tough and able to withstand harsh conditions, the absence of certain species of lichen is a red flag for biologists: the cleaner the air, the higher the quality of the lichen species. It’s also interesting that 1,300 million years ago, lichens were the first fungi to team up with blue/green algae. The photosynthesis which produced the oxygen which was released into the atmosphere paved the way for the evolution of life on earth, not to mention the soil that came from the breakdown of rocks by lichen.

Where large or overhanging branches are concerned, those covered with lichen stick out like a sore thumb in the summer months. This is another helpful hint that such safety hazards need to be removed if they can fall on humans or buildings. In these cases, as in most others, lichen is not the culprit for the dead limbs but merely taking advantage of areas with more available sunlight. Other than these examples, no control is required or recommended.

So, when you notice lichen on your shrubs and trees, try not to think of it as something that is harming the plant, but as a helpful hint that maintenance may be due. Notice whether some of the stricken plants reside far from the garden hose or perhaps were planted where the soil is not the best.  Identify those plants and trees and prune, mulch, or install that watering system you’ve been thinking about. While it might be a stretch for gardeners who like things neat, lichen can be one of your best garden tools.  What’s not to like about that?

Jane Falkenstein is an Extension master gardener volunteer in Haywood County. For more information, call the Haywood County Extension Center at 456-3575. © 2014 NC State University.