By Bev Johnson

Master Gardener

Scientists view the interaction of plants, fungi and bacteria as a “co-evolutionary” arms race.  The result of this arms race is that plants die of various diseases, even though  “truces” are usually the norm. the result of these truces is that neither has the upper hand.  Plants and fungi, in some instances, seem to be able to happily co-exist. One of these happy co-existences resulted in the development of lichens.

Lichens are the result of a symbiotic relationship. The definition of this relationship is “the living together of different species of organisms which may or may not be to their mutual benefit”.

Organisms that live together in ways that are mutually beneficial (mutualism) are like the college roommate who helped you through biology. The opposite is parasitism where one organism benefits to the detriment of the other, like the boyfriend you had to have the cops remove from your apartment.

A lichen is not a single organism in the way most living things are. In fact, they are a combination of at least two or even three organisms that live together. An algae or cyanobacterium provides food through photosynthesis. Most of the fungi that co-exist as lichen produce a cup-shaped disc for reproduction.  The fungus and algae that make up a lichen may each be found living, almost microscopically, without a partner, but the beauty that results when they make an alliance is remarkable. Some of the more enterprising fungi have multiple partners and colonize more than one species of algae. Then there are the fungi that are completely dependent on its algae. Actually, the algae get very little out of this partnership. One smart aleck lichenologist said, “lichens are fungi that have discovered agriculture.” Or maybe, lichens are fungi that have discovered slavery.

Lichens are composed of several specialized parts, a protective layer of fungal tissue called a cortex that protects the algae or cyanobacteria. Below this is a layer of loose fungal thread. The fungus provides mineral nutrition by decomposition and the algae provides the majority of the food.

Like other organisms, lichens are identified and classified based on their looks. Crustose lichens produce tightly formed, colorful crusts that stick to fences, rocks, sidewalks and trees. You can’t remove them without damaging whatever they are stuck to. Leaf-like lichens are called Foliose. They are rather loosely attached. The best known are the fruticose lichens. They look like little shrubs. They can also hang down in long strands from trees.  Squamulose lichens have scale-like lobes called, surprise, squamels that are usually overlapping. British soldiers is the name of a lichen where the base is squamosal and the showy part is fruticose. 

Lichens are the most overlooked of the conspicuous organisms in the landscape. It is unknown how many different species of lichens are present in Minnesota.

The information for this article is from one of Janna Beckerman’s, an Extension plant pathologist. Bunkey got lost in the second paragraph.

Now that the snow is melting, occasionally, do check that your perennials are still covered with snow.  Plants that are uncovered are exposed to  frost heave and  that can lead to dehydration of the roots,  a sure death. Get the shovel out and cover them up until all the snow is gone. This is especially important on the tops of hills as they usually melt first.

If you haven’t pruned your fruit trees yet, get with it. Soon it will be too late and you will do more damage than good.