Which plant is able to withstand a temperature of -70 degrees as well as +70 degrees?
This is lichen, a very resistant composite organism, capable of living in extreme conditions.
There are more than 20,000 species of lichens.
They are present both in the polar regions (Arctic, Antarctic) and in the desert, in the mountains, in the plains, on rocks, lava, small concrete walls or metal posts... In our gardens, we found on trees and shrubs, they sometimes invade trunks and branches.
Should we be worried about it?
To discover
What to plant, sow or harvest in March?
Why is there lichen on trees?
Lichens are a symbiosis of fungi and chlorophyll partners, most often green algae, sometimes cyanobacteria
.
According to Larousse,
“the fungus provides the algae with shelter which protects it against the sun's rays.
In addition, by retaining water in its tissues, it prevents it from drying out.
In return, the algae provides the fungus with the organic molecules it produces through photosynthesis, as well as vitamins that stimulate its growth
.”
It is therefore a beneficial association for the survival of both organisms.
Lichen, made up of 90% of the fungus, has the particularity of having neither root, stem nor leaves.
Certain lichens therefore colonize trees to develop, using the trunk as a growth support.
They are epiphytic organisms, meaning they grow on other living things.
They grow very slowly on the bark.
Good to know
Lichen is often confused with moss.
The difference is that the latter is an evergreen leafy plant, unlike lichen.
In addition, the latter has a silver or golden color when dry.
Can the presence of lichens on a tree threaten its survival?
Contrary to popular belief, lichen is not a threat to the survival of the tree or shrub.
It's not a parasite for him.
It certainly attaches to the tree but it only remains on the surface, without penetrating the tissues or drawing sap.
And it doesn't prevent the bark of the tree from playing its role either.
Lichen therefore does not interfere with the development of trees because it does not drain any nutrients.
Its presence also does not mean that the tree is diseased or in poor condition.
This composite organism may have a bad reputation because lichen is also a skin disease...
Lichen finds the elements necessary for its growth directly in the atmosphere: it absorbs rainwater or atmospheric water vapor, which contain minerals.
Did you know ?
Since lichens do not have a protective system, they also absorb air pollutants.
They are therefore bio-indicators of air quality.
The more lichens there are, the less pollution there is!
Lichens shelter certain insects in winter.
A valuable pantry for birds.
The only risk that lichen poses could be that it masks possible fungi that could harm certain species, such as fruit trees.
How to remove lichen?
If you want to better observe the condition of your fruit trees or consider lichens unsightly, you can brush the bark of the tree.
To do this, use a suitable tool that will not damage it, such as a brush with non-abrasive bristles.
In the case of a diseased tree, you can remove the lichen on the surface to be treated and then apply a lime-based treatment.
For better efficiency, it is recommended to do this operation when it is not raining.
Also note that preventive liming of fruit trees helps prevent diseases, as well as the appearance of lichen or moss.