It says a lot about how dreich and colourless the past few weeks have been that I’ve found myself seeking out texture and form in familiar places.
As a result, I find I’m seeing my usual surroundings in a different light.
I know the Linn of Dee woodland very well, as I’m in it almost every day. But, while I’ve certainly noticed its lichens before, I don’t think I’ve ever noticed them as keenly as I have this past week.
Apparently, lichens cover 7% of the world’s surface – and, if this woodland is anything to go by, I can well believe it. The bottom half of every single Scots pine is blue-grey, as though it’s been dipped in paint.
From a distance, it’s easy to assume that the colour comes from one, singular lichen species. But, when you look closer, you notice strings, tubes, cups, leaves, trumpets and tassles. There is so much texture to see, because each tree is home to whole communities of different lichens.
There are over 1,800 lichen species in the UK, and while identifying them at a species level can be a terrifying challenge, lichens can handily be grouped into three principal forms: crustose, foliose and fruticose.
Such terms probably sound weird and alien, which is a fair assessment of a world which also speaks of theciums, hapters and goniocysts. But bear with me, because the first two forms are actually rather intuitive in terms of what they describe.
From Heather Rags to Old Man’s Beard
Crustose lichens are… crusty. Generally, they form thin patches, so firmly attached to the surface below that they can look more like stains or a bumpy rash. I particularly like the crustose lichens you find on rocks in the high hills, as they’re surprisingly colourful.
A particular favourite is map lichen. Bright yellow, each one has a defined black border. When they pack together on a rock, collectively they look like imaginary countries drawn on a map.
Foliose lichens are, indeed, like foliage. They’re leaf-like, and often lobed. It’s the blue-grey ones, such as the aptly named “Heather Rags”, which so comprehensively coat the heather and Scots pines at Mar Lodge Estate, and have caught my attention this past week. In Fife, I’ve seen long-tailed tits pulling great clumps of it up, and using it to camouflage the exterior of their nests.
Common orange lichen is another foliose lichen you’ll undoubtedly have seen. Bright orange, it vividly coats rocks along the coast.
Fruticose lichens are nothing to do with fruit. The name instead derives from the Latin for “bushy”, and these lichens are typically stringy, fibrous, tassle or shrub-like.
It’s the fruticose lichens hanging from trees that most readily capture our imaginations in Scotland – affectionately referred to as “Old Man’s Beard”, this actually describes any “beardy” lichens from the Usnea genus. When these beards cover every square inch of a tree’s branches, their luminous fuzziness denies the trees any hard edges, and makes them look almost ghostly, as though they’re not quite there.
They’re not plants or mosses
Beautiful as they are, lichens are quite the things to get your head around. They’re not plants and, despite several species having “moss” in their names, they’re not mosses either. They’re in a category all of their own and are, in fact, composed of two organisms – a fungus and an alga.
The fungus gives the alga a home, offering protection from sunlight and desiccation. The alga is able to photosynthesise, using sunlight to produce carbohydrates, which the fungus uses for food.
Because lichens get their nutrients, minerals and water from the air around them, they don’t need soil. This means they’re able to “pioneer” in places devoid of soil, but it also means they dry out easily.
Many a hillwalker will have both felt and heard Reindeer Moss (not a moss!) crunch underfoot during a dry spell. Lichens can, however, weather such extreme conditions, and rehydrate quickly when moisture becomes available.
In that sense, they’re among the hardiest organisms on the planet. But they’re also precariously fragile. Because of the way they obtain nutrients, most lichens are highly susceptible to airborne pollution, notably to sulphur dioxide and nitrogen dioxide, which are produced by industry and vehicles.
Profusion and diversity of lichens in a given location, therefore, is generally a sign of clean air. But that’s also why you won’t see trees “dripping” with lichens in our larger towns and cities.
That’s a shame, of course, because in a season often regarded as being rather lean in terms of natural distractions, lichens can offer something of a lifeline.
As someone on Twitter remarked to me a few years ago: “I used to work for the Field Studies Council ‘up north’, and the lichen on birch got me through the winter. It’s like secondary foliage giving you life”. I couldn’t agree more!
Ben Dolphin is an outdoors enthusiast, countryside ranger and former president of Ramblers Scotland
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