The value of lichens in environment
|Shown is a photo submitted by a reader regarding a substance growing on his trees. Garden writer Dayle Davis said it appears to be a healthy colony of lichens growing on the trees. However, she advises to consult an arborist who can provide an on-site evaluation and a positive identification.|
|Photo courtesy of Larry Goodman|
The published data about lichen life forms is fairly scientific and a bit of a boring read, so presented here is my best effort to explain the nature of lichens in simple layman’s terms:
Lichens are not a moss. They are not a plant at all, nor an animal. In general, lichens are lesser known members of a vegetative body of life forms. There are several different physical forms for lichens besides the one I have described above, such as leaf-like flattened layers; a three-dimensional pendulous form; and a thick, rough, crust-like form with patches of bright colors, among others.
A lichen in any form is a plant-like organism actually formed by two (and sometimes three) different species — a fungus and an algae. The fungus and algae work together to survive in a mutually beneficial relationship that is technically referred to as a “mutualistic symbiosis.” Or, as I like to describe it, “You scratch my back and I’ll scratch yours.”
Here’s how that works:
The algae produces sugars through photosynthesis, which feeds the fungus. The fungus, meanwhile, provides moisture that helps to protect the algae and also helps it to get the most out of its photosynthesizing efforts.
Lichens exist worldwide from mountaintops to valley lows. They survive in any climate — from sweltering to arctic freezing. Different lichens may have different specific environmental requirements in order to flourish. Some will grow only on organic surfaces such as bark, wood, moss and soil. Others will grow on surfaces such as plastic, cloth, metal and glass. But, in general, all lichens require a span of time to develop on an undisturbed surface surrounded by clean air.
The ecological value of lichens is beyond measure. Among other attributes, lichens:
• play an important role in soil formation;
• contribute to the beneficial nitrogen cycle of other plant life;
• are the preferred nesting material of 50 species of birds;
• are the preferred food source of caribou and reindeer;
• provide food for slugs, snails, moth caterpillars, worms and more; and
• serve as the exclusive diet of certain moth larvae; and
• provide camouflage and shelter for small animals.
More than 600 substances have been extracted from lichens, which help the organism to survive as well as substances that:
√ were used in antiquity as dyes for Roman togas, Scottish kilts and Native American rugs;
√ are still used today as natural dyes for wool and fabric;
√ are used as teas and salves in traditional medicine;
√ are used commercially in ointments for their antibiotic properties;
√ are sensitive to sulfur dioxide, absorb nearby pollutants and are tested chemically by scientists to analyze the air;
√ are being researched for fighting certain types of cancer and viral infections;
√ are used by archaeologists to date artifacts and follow the course of geological events;
√ are used as a fixative in perfume; and
√ are widely utilized in the ornamental horticulture industry.
Contrary to popular belief, lichen does not damage the shrubs, trees or other plants it grows on. It doesn’t damage the bark or deprive it of moisture. It does not act as a parasite to the plant. It does not provide an entry point for pathogens.
If a plant is ailing or in decline, however, the lichen may multiply simply because less foliage means more sunlight reaches the lichen and more photosynthesis can occur, which helps to grow more lichen.
Remember: Lichen is not an unsightly disease that attacks other plants. Rather, mankind is a huge threat to lichen through pollution, drainage, deforesting, land clearance and the chemical applications of fertilizer and weed control.
It’s easy to feel suspicious about anything you don’t recognize in the garden. Years ago I remember giving a wide berth to any tree or other surface that lichen grew on. I was convinced the layers of crust would suddenly unfurl like the shutter of a camera to emit a hideous insect that sent me screaming from the garden in search of the closest chemical spray. Imagine my chagrin once I learned about this valuable organism in a Master Gardener class.
A good gardening rule of thumb is to always be sure to identify what you are dealing with before taking any action. Availing oneself of knowledge is the best resource to help preserve the environment when it comes to the garden.
There is an interesting quote in the fact sheet referenced below that helps to put the value of lichens in perspective:
“Discovering a lichen growing on your tree is not a bad thing. In fact, it should be celebrated by giving you peace of mind knowing that the environment in your neighborhood is clean enough to support this amazing dual organism.”
For more information, call the OSU Summit County Hotline Tuesdays from 9 a.m. to noon at 330-928-4769, ext. 3. Request Special Circular 195, FactSheet Ornamental Plants Annual Reports and Research Reviews 2004, 10 Things You Should Know About Lichens.
Dayle Davis is a freelance writer and avid perennial gardener, with a B.A. in communications and course work in botany, geology and wildflowers. Davis is certified as a Master Gardener under The Ohio State University’s Horticultural Extension.
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