While my friend Ann Nolte walks briskly through her woods outside St. Matthews, I am hoping she will stop to identify a perched bird. I will then have a chance to inspect the works of nature that stand still. Hearing loss from cutting grass while renting at historic Ashtabula during my Clemson days as well as 60 years of wearing eyeglasses limit my interest in birding. Standing in one place, I love using a hand lens or extremely close-focusing binoculars to view all sorts of intricacies on organisms. Among my favorites are lichens.
As a Clemson Extension agent, I’ve talked to hundreds of people who call our office distressed in their belief that lichens are killing their plants. I patiently convince them that these often highly visible structures are not parasites and are doing absolutely no harm to the shrubs or trees where they are growing. About the worst thing you could say about them is that they are opportunists taking advantage of what amounts to a park bench in the sun.
Lichens are photosynthetic lifeforms that are classified as part of the fungal kingdom, but they are actually two separate organisms growing as one. The body of a lichen is composed of a fungus that has developed a symbiotic relationship with a photosynthetic alga or a cyanobacterium, those last two of which on their own must live in a moist or aquatic environment. Through some remarkable evolutionary process, certain fungi and algae developed the ability to merge into an organism with some plant-like characteristics.
In general, fungi are the scourge of gardeners and farmers. Without chlorophyll or other photosynthetic pigments, they are decomposers, and many invade plants and feed on the decaying roots, stems, leaves, flowers, or fruits that they attack. However, when a fungus becomes intimately integrated with an alga, it no longer has to act as a parasite to get its food. The fungus creates a nurturing body — a thallus — that provides structure for the alga, enabling those cells to live outside of their normal aquatic habitat. The structural body of the lichen basically envelopes the photosynthetic cells, holding them in sunlight and absorbing moisture (and certain nutrients) from the atmosphere.
From the tundra of Alaska to the deserts of Arizona, lichens occupy niches where other organisms would perish. Unlike most plants, lichens can become desiccated during times of drought and reconstitute themselves when water returns, a condition with the wonderfully fun name poikilohydry. Since they don’t get nutrients from the soil or from the plants on which they may grow, certain species can live on tombstones just as well as a tree branch. Some lichens actually grow on top of the soil.
The “reindeer moss,” so plentiful on nutrient-poor sands in parts of our state, is a form of lichen. I collect clumps of them to use as filler around the edges of flower arrangements. Most of the time they are as dry as toast would be if left too long in the oven, but after a rain they become completely soft and pliable so that pine straw and debris clinging to their underside can be picked out much more easily. In the tundra regions, their common name is well-deserved as they are a major food source for the grazing inhabitants of those often-frozen plains.
Almost all lichens are edible, but they have an extremely high acid content and must be boiled or soaked to lower that compound before any attempt to eat them. Historically in Scandinavian countries, they were used in making such liquors as Aquavit. In Scotland, their usefulness as dyes was critical to the original fabrication of Harris Tweed material.
As rootless organisms, lichens must absorb all their water and certain nutrients from the atmosphere, rendering them extremely susceptible to air pollution. With a life span of often thousands of years, they serve as bioindicators of air quality. Large quantities of toxic materials in their ecosystems can lead to their death.
The concept of lichens being the canary in the coal mine for urban pollution has a long history. William Nylander in 1866 published a study about the Parisian Jardin de Luxembourg in which he noted that the center of that large urban green space had the greatest diversity and number of lichens compared to surrounding areas. Today, the U.S. Forestry Service monitors lichens as part of a study on trends in air quality.
If you are fortunate enough to have access to a place in the country where plum thickets eke out a living on poorer soils, keep your eyes open for certain areas where those crowded colonizers grow so tenuously that they become covered with a certain type of lichen that has an affinity for those specialized locales. I have several places where I pull off the roadside to collect these somewhat tortured looking, twiggy-branched structures that are covered with specimens of my favorite lichen, Usnea strigosa, with the common name of Old Man’s Beard. Nothing is a more beautiful harbinger of spring than an arrangement of early daffodils with these lichen-covered plum branches added for height and contrast. You can see a picture of this and other lichens you’re likely to encounter in our part of the world by searching “A Guide to Twelve Common and Conspicuous Lichens of Georgia’s Piedmont.”
Some true plants don’t have roots in the ground, and they, like lichens, use other plants or non-organic structures to get into the sunlight. Pleopeltis polypodiodes, commonly known as resurrection fern, grows in trees with open canopies (pecan trees are perfect spots as are larger, spreading live oaks) from New York over to Texas. When we think of ferns, we usually picture shady moist groves or hanging baskets under the eaves of porches. But this remarkable epiphyte can lose more than 75 percent of its water and look like it long ago passed the PWP — permanent wilting point — after which most plants are considered kaput. But within hours of being thoroughly moistened by a slow, penetrating rain (or being soaked in a bowl in your kitchen as a demonstration for your kids) resurrection fern completely rehydrates and is as fresh as a daisy. Don’t look for any flowers, however, as ferns reproduce by spores.
Although they have no actual roots, resurrection ferns do have rhizomes, specialized stem tissue, which in this case threads its way through small openings in a tree’s exterior bark where it both anchors the plant and also aids in absorbing water and dissolved nutrients. The chlorophyll-containing green leaves take advantage of their elevated space in the tree canopies to absorb sunlight. Occasionally you see this plant growing on rocks or bricks, providing evidence that when found in its usually arboreal perch, it’s taking no nutrition from its host.
Not so with the truly destructive and very common plant pest the hemiparasite Eastern mistletoe, Phoradendron (meaning tree thief) leucarpum. In Nordic and Druid mythology and in pagan rituals of Western Europe, this plant was placed on a pedestal, so to speak, for its powers. Growing on mighty deciduous oaks, it was highly visible in the winter months and was collected using special tools and cloths for ceremonies. When warring tribes encountered each other under mistletoe-laden trees, an automatic truce was observed. Perhaps that gave rise to the belief that when brought into homes it could promote harmony between bickering spouses and increase their chances of conception.
This flowering plant has male and female sexual structures on separate plants. When fertilized, the female flower develops into a remarkably sticky fruit surrounding the seeds. Birds, especially our ubiquitous mockingbird, feast on them but then try to wipe the mucilaginous flesh off their beaks on nearby branches. The seed first germinates into the host plant stem, establishing a root-like structure called a haustorium. Secondary growth produces the green, branched, photosynthesizing leafy portion, which does, especially in winter when the host plant is usually leafless, engage in photosynthesis. It may not sound so bad, but the haustorium eventually kills the portion of the branch above the point of attachment.
Equally harmful is the drain on the host plant’s stored reserves during winter, leaving it in a weakened state after periods of less than optimal growing conditions. In urban street plantings, often with one or two species predominating, birds can easily spread the seeds to one of the over 100 suitable hardwood host trees for this pest.
Cutting off the visible portion of mistletoe won’t kill it. You must remove the branch at least a foot back below the point of attachment. In some cases, you can remove the female structures and slow the spread of this parasitic plant. In the countryside, the time-honored way of collecting mistletoe is to shoot it out of a tree with a shotgun. This is not conducive to a healthy pruning cut, however.
Instead, look for some on an already half-dead Bradford pear and collect mistletoe there. If you want to have a mistletoe ball for stolen kisses at Christmas, do keep in mind that it’s highly poisonous to humans. Birds and caterpillars, however, which evolved with this Eastern U.S. native plant, are not harmed by its toxic compounds and eat fruits and leaves with no ill effects. We are fortunate that our Eastern mistletoe only parasitizes hardwood trees. A Western genus attacks conifers and has exploding seed pods, to boot.
The most conspicuous aerial occupant of trees and shrubs in the lower half of our state is Spanish moss. A flowering plant with small green blossoms (you have to be looking frequently in the spring to see them; the seed pods are much easier to spot), it produces all its energy requirements from photosynthesis, just like lichens and resurrection fern, and absorbs water and certain air-borne nutrients through its stems and branches. Under the gray-green scales is a strong, black, wiry stem.
When the South was in its bleak economic crisis for the many decades after the Civil War, people collected this moss, treated it to expose those stems, and actually baled it like we do cotton today. Parents would place their children in the branches of trees to loosen these plants and drop them to the ground. Mattresses, upholstered furniture, even the seats of the Model T Ford, were stuffed with treated Spanish moss. Today it is used for crafts and flower arrangements.
People call me worrying that they’ll get red bugs if they pick it and tell me they put it in the oven to prevent that. You might indeed get chigger bites from standing in pine straw while gathering it, but please put this living plant in the freezer, which won’t kill the plant but will render it pest free.
Spanish moss, the most common example of this genus of airplants in our state, has the botanical name of Tillandsia usneoides. Some scientific names have good stories behind them. Fox example, the great Swedish botanist Karl Linnaeus chose Tillandsia as the genus for this complex group of bromeliads to honor Elias Tillandz. The Finnish professor some 60 years before Linnaeus wrote a botanical treatise. For the specific epithet of Spanish moss, our Swedish botanist crafted the word usneoides, which means “looks like usnea,” my favorite lichen native to our state. Here we have the father of the binomial system of classification naming a true plant but one without roots that must hitchhike a ride into the tree tops in order to photosynthesize after another photosynthetic organism, which is not a plant at all, and actually consists of two completely separate and unrelated life forms merged together.
As you walk through the woodlands near Columbia, you can find examples of both true plants and lichens growing in the same ecosystem amid the treetops. Each is using its host plant as a way to position itself to absorb sunlight, powering photosynthesis — the basis of all foods we consume. What an incredibly complex world we live in, with its different pathways and ways of organizing life.