What We Can Learn From Lichens In Garden

Max's Walden is full of lichens.  

I wondered what are these lichens and why are so many of them here? 

I have the answer now and it's good news!

Which lichens are present in our gardens can tell us a lot about the conditions that are present. In particular, they are known to be useful indicators of air quality.

Lichens get their nutrients from the air and cannot filter what they absorb, so they are commonly intolerant of air pollution. This means that we can see how polluted air is by looking at the lichens present in our gardens. As a general rule, the smaller and less varied the lichen in an area, the more pollution there is in the air.

Lichens can, in particular, tell us about the presence of nitrogen dioxide and sulphur dioxide. When it comes to nitrogen dioxide, some lichens will thrive in its presence, while others will die. Crustier lichens tend to be hardier than hairy or leafy-looking types. Where there is a lot of nitrogen, crustier lichens will thrive. So, seeing these can be a sign that there is a lot of nitrogen dioxide around from traffic or farms.

Sulphur dioxide pollution comes from coal burning and industry. Where there is a lot of this pollutant in the air, lichens will often die. If you have hairy lichens growing where you live, then this is unlikely to be a problem.

But is lichen an indicator of problems when it grows on trees? Does it pose a threat to the tree or show that something is wrong? No, lichen does not harm a tree. There is absolutely no need to get rid of it, and trying to do so may do more harm than good.

Dead or dying trees may be the perfect habitat for lichens, due to the more open canopy letting light through and the moist conditions. But lichen can also often grow on perfectly healthy trees, so the lichen itself does not indicate a potential issue.

Don't be tempted to try to eradicate lichens from trees or other locations in your garden. Just learn from the lessons it has to teach us, and be aware of what it has to tell us about the air quality where we live.