By Susan and Biff Andrews

We hope you like lichen, because we’re talking about it again this week.

Because only certain algae and certain fungi can get together to form a lichen, each fungus and alga form a unique type of thallus body; scientists can use this thallus body to help name them and make identifications.

Identifying lichens is much more difficult than identifying vascular plants. Each lichen thallus is a complete microscopic world with unique characteristics separating it from the other lichens. They are classified based on the fungus they derived from and the features of that fungus.

There are an estimated 13,500 to 17,000 species of lichens; they are found in every geographic region, climate and terrain on the planet.

There are three main types of lichen, and they come in a variety of interesting shapes, sizes and colors. Moisture seems to have an effect on color.

Foliose Lichens are leafy, like lettuce; Fruticose Lichens are the hairy-looking ones that hang off branches; and Crustose Lichens, are the flat, crusty-looking ones that like to cover a surface like a boulder.

A lichen will grow on just about anything. Sometimes they grow on trees to use them as a support (substrate), but they are not parasites. Every lichen lives on top of something else. The most common natural substrates are trees, rocks, and soil. But they will grow on most anything manmade that has been sitting around outside for a while.

Many lichens are sensitive to pollution in the air and are a good indicator of air quality. When there are too many harmful things in the air, lichens die. If you live where there are lots of lichens, it probably means the air is pretty good.

Lichens are important in many ways in the habitat. Some make the nitrogen in the air usable to plants. They are also home for spiders, and other insects. All are important in the nutrient cycle in the places where they grow, and many animals eat them.

Humans have learned to use lichens in many useful ways. In some cultures, people eat lichens (some are poisonous so don’t even think about it!). Drug companies make antibiotics from lichen substances. Weavers sometimes use lichens to make dyes to color wool.

Unlike plants that can produce seeds that grow into new plants, lichens do not have a direct way to grow more lichens. Since the fungus is the dominant partner in the relationship, it gets to develop its fruiting bodies and produce spores. These spores can produce another fungus, but sadly for the alga, it doesn’t get a chance to reproduce at all. Either the new fungus has to find an algal partner or it dies.

But wait… lichens have found a way around their dilemma. These organisms can reproduce vegetatively; That is, they have structures specifically developed for the spread of fragments of their thalli which contain both partners, so simple fragments can grow into full-size lichens.

Lichens are fascinating to look at … we spent hours in the swamp in preparation for this article looking for and photographing their many interesting forms and habitats. Once our eyes got accustomed to finding them, we were hooked and couldn’t stop looking for them…it was as habit-forming and as fun as looking for shells or sea glass on a beach.

Many people collect lichens. In fact, there are databases devoted to lichen identification. Some lichens are rare and federally protected, so you need to be informed before you start collecting anything, and be advised that you can’t take anything from state or federal land except pictures.

Next time when you are walking through a park, pay attention. Before you know it, you’ll be likin’ the lichen.

Susan and Bradford “Biff” Andrews are retired teachers and master naturalists who have been outdoor people all their lives, exploring and enjoying the woods, swamps, rivers and beaches throughout the region for many years. Email them at b.andrews22@live.com.