lichen is an unusual organism composed of a fungus and an alga living together
symbiotically. The alga converts sunlight and carbon dioxide in air to food.
The fungus surrounds the alga, protecting it from drying, and lives off the
food it provides. Lichens appear as green to gray-green leafy or crusty growths
on the trunk and branches of trees in poor health. They are totally harmless
and are in no way responsible for the poor health of the tree. The reason they
are associated with declining plants is that as woody plants loose vigor and
decline, the number and size of leaves decreases. This allows more sunlight,
which lichens need to grow, to reach the trunk and branches.
plant health is restored by correcting the real cause of decline, leaves will
increase in size and number; less sunlight will get to the trunk and limbs; and
lichens will gradually disappear.
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