Lichens come in a range of odd shapes and varieties. But what exactly are these splodgy badges of colour?
Here’s what you need to know about lichens and seven species you can spot on trees.
What is lichen?
Lichens are actually made up of two or more different organisms. These exist in a mutually beneficial relationship called symbiosis. So you can think of lichen as a successful partnership, between
- a fungus
- an algae and/or cyanobacteria.
The fungus element requires carbohydrate as a food source. The algae or cyanobacteria on the other hand require shelter. As the algae/cynaobacteria are photosynthetic they provide the food for the fungus in return for that shelter. It's a partnership that works.
Where to see lichen
You can see lichen in lots of places - with little blazes of colour cropping up on rocks, walls, twigs, bark and even on exposed soil surfaces. Different kinds of lichens have adapted to survive in some of the most extreme environments on Earth: across arctic tundra, hot dry deserts and rocky coasts.
Lichens are non-parasitic and don’t harm any plants they grow on. In fact, they’re useful to other wildlife, offering nesting material for birds, and food and shelter to lots of invertebrates - which in turn feed other creatures. Woods rich in lichens support more wildlife than any other.
Lichens can be big and bright or small and dark. What’s more our amazing lichens can take on a variety of shapes and forms like:
- bushy beards
- crusty spots
- leafy pads
- even small standing branches.
Lichens are also sensitive to pollution and can highlight the quality of the surrounding air. Crusty lichens are hardier to pollution, whereas the more delicate beard-like ones are mostly found in cleaner locations and are rarer.
The close relationship between lichens and ancient woods and trees
Ancient woodland is land that has been continually wooded for a very long time.
Because of this, ancient woods are particularly important for lichen as they provide an undisturbed environment where lichen can thrive. Lichens need this as they take a long time to develop, growing only 1-2mm a year.
Some species of lichen require alkaline conditions and are only found growing on old bark. Bark can become more alkaline with age, so species such as ash – which has a relatively high pH (alkalinity) of bark - are home to a lot of species. In fact, some 536 lichen species are associated with ash!
All of this really underlines how crucial a single ancient tree can be for our varied lichen species.
Seven common lichens you can spot on trees
There are lots of different types and they can be difficult to identify, so here’s our guide to seven lichen species you can find in our woods and forests.