There is a gravestone in a churchyard near where I grew up that is covered, on its north-facing side, with a lichen so old it predates anyone who might remember the person buried beneath it. The stone dates from the 1780s. The lichen may be older still, or it may have colonised the stone gradually in the decades after. Either way, it has been growing there — slowly, enormously slowly — for the better part of two and a half centuries.
I find this extraordinary. I am not sure I have entirely worked out why.
What Lichen Actually Is
First, a clarification that tends to delight people who encounter it: lichen is not a single organism. It is a partnership — a symbiosis between fungi and photosynthetic partners, usually algae or cyanobacteria, sometimes both. The fungus provides structure and protection; the algae produce food through photosynthesis. Together they can survive conditions that would defeat either partner alone: Arctic rock, bare desert stone, the surface of roof tiles, the bark of trees in polluted cities.
There are somewhere in the region of twenty thousand known species. They vary enormously in form — the flat, crusty crustose lichens; the leaf-like foliose lichens; the branching, almost plant-like fruticose lichens. What they share is a kind of radical patience.
The Slowness
Growth rates in lichen are typically measured in millimetres per year. For some species, particularly those growing on exposed rock in harsh conditions, the rate is closer to millimetres per decade. A crustose lichen the diameter of a coffee cup may be several hundred years old.
Scientists have used this fact to date geological and archaeological events — a practice called lichenometry. The principle: measure the lichen, know the growth rate, calculate how long the surface has been exposed. It is not a precise science, but it is a remarkable one. Lichen becomes a clock. Slowness becomes information.
What It Feels Like to Look
I have started, in the last few years, to actually stop and look at lichen when I encounter it. This requires an adjustment. The human eye, accustomed to motion and novelty, tends to slide over lichen. It looks static. It looks like texture rather than life. You have to hold your gaze on it for a moment before something shifts.
Then you begin to notice the structure. The intricate, almost fractal branching of a Cladonia on a forest floor. The grey-green rosette of a Parmelia on a dry stone wall, perfectly circular, growing outward in all directions at the same imperceptible rate. The astonishing orange of Xanthoria parietina on a seaside rock — one of the most common lichens in Britain, and one of the most beautiful, if you will only look.
Patience Is Not Passivity
What I find myself thinking about, when I think about lichen, is the word "patience." We use it to mean something slightly passive — endurance, waiting, the absence of complaint. But lichen is not passive. It is actively colonising. It is producing acids that slowly dissolve the rock beneath it, deepening its hold. It is building structures of tremendous complexity. It is doing all of this at a speed our minds struggle to register as movement.
Perhaps patience, properly understood, is not about waiting at all. It is about working at the rate that is available to you, without demanding a faster one.
The lichen on that gravestone has no opinion about its own slowness. It simply continues. Two hundred and fifty years, give or take, of simply continuing. There are worse things to contemplate on a Sunday morning, crouching beside a stone in a quiet churchyard, trying to learn something.