Plant of the Week??? Lichens

Lichen growing on willow bark

Lichens are not truly plants, they’re not even a single organism.  These crusty, sometimes mossy looking things growing on trees and rocks are actually an algae and a fungus living together.  The fungus (mycobiont) gets nutrients from its substrate and gives it to the algae (photobiont), and the algae makes food (carbohydrates) through photosynthesis and gives it to the fungus.  I use the word “gives” liberally, some would argue the organisms are stealing from each other. 

Lichens live in some harsh places on earth, surviving intense ultraviolet radiation and temperatures in excess of 130°F, and eat bark and rocks.  That’s pretty hardcore.  That makes it ironic that they are good indicators of pollution.  Lichens are susceptible to pollution found in rain and the air.  They have no true roots and must take in all their moisture from the air.  They don’t have the luxury of the filtering effects of soil.  I don’t really think of Oshkosh as a big dirty city, but its lack of lichen diversity indicates that there is more pollution than the countryside.  Today, pollution is less visible.  We might not notice any sources if it were not for the water vapor visible from our tail pipes and furnace exhaust on cold days, but it is there and does have an effect on everything and everyone including the toughest organisms on earth.  

Lichen growing on living ash bark