The start of February, marked by the pre-Christian festival of Imbolc, later absorbed into St Brigid’s Day, carries with it a promise: winter has loosened its grip, making way for the relief of brighter days. But it’s a period of in-betweenness and restraint; a month of pauses, when the light lingers and lengthens imperceptibly, yet the air is still damp, the ground cold, the promise of new growth and life – “the soft fire of the bud”, in Emily Dickinson’s words – held rather than displayed.
Meteorologically, of course, we’re still in the depths of winter, a fact brought home while standing in a field in the driving rain on a farm in rural Westmeath during the week. Even the blackbirds and wrens, restless in the damp and unyielding weather, seemed fed up as the wetness pressed down. Their songs, far from sweet, fecund, and spring-like, were tense, high-pitched, sharp cries of alarm. No doubt they were reacting to my presence, but their calls somewhat reflected my mood; I felt like replying, “I hear you! I’m sick of these dark, cold days too”.
On overcast, rain-heavy hours such as those, the land appeared all but drained of colour, flattened beneath a blanket of cloud. A sentinel line of leafless trees extended the length of the field, held back by a fence. Their boughs reached far enough to attract the cattle, who, in a display of better judgment than mine, plodded over together and huddled for cover. Moisture darkened the land, but against sodden earth and grey clouds, one tree stood out as if illuminated from within: it was dripping and bearded with soft, bushy tufts of the mint-green oakmoss lichen, Evernia prunastri, waving in the wind.
[ If this lichen is growing in your area, it means the air you breathe is cleanOpens in new window ]
I like to think of lichens as an enduring, intense love story between a fungus and an algae. Sometimes a cyanobacterium joins in instead of the algae, and occasionally it becomes a menage a trois, with all three partners setting up shop together. If the fungus is the house providing shelter, the algae are the inhabitants that give back by producing sugars. The fungus secretes pigments that stain with greens, yellows, blues and rusty reds, injecting a kaleidoscopic vibrancy into otherwise drab days. They unite as one, bound so tightly that separation, particularly for the fungus, would be fatal. Their lives are tiny, self-contained, slow-growing worlds.
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Beyond this, lichens are ecologically vital as biological indicators of air quality, providing an early warning of pollution and offering habitat and nourishment to countless invertebrates, nonlichen fungi, nematodes and bacteria. No leaves, no soil, no flowers, no stems or roots – all they need is sunlight, moisture, clean air and lots of time.
A few miles down the road, I stopped off at St John’s Church in Ballinalee, Co Longford, where weathered gravestones, some dating from 1835, commemorate the dead, yet life clings to them in the form of white and grey lichens, as if the stones have been splattered with large flecks of Tippex or white paint. Churchyards, cemeteries, ruined abbeys and boundary walls often become lichen havens, especially when safe from disturbance, chemical sprays and fertilisers.
According to the British Lichen Society, more than 600 lichen species – including many endangered and rare ones – grow on churchyard stones in lowland England, and a single churchyard can host more than 100 species. Gravestones, whether marble, limestone, granite, sandstone or slate, create a multitude of niches where different lichens can live. Some lichens can even eke out a home in the nooks and crannies of recessed lettering, a space often favoured by the yellow Psilolechia lucida, the sulphur dust lichen.
A recent ecological study suggests that the lichens clinging to dry stone walls (boundaries that may look inert but are quietly alive) tell a larger story about how we farm the land around them. A 2022 study published in Ecological Indicators examined lichens and mosses on stone walls on 16 farms in northwest Ireland and found that these organisms closely reflected farm management practices. Walls on lightly managed farms, where fields were grazed less intensively, fertilised sparingly and retain more landscape features, supported higher species richness and greater cover of lichens and mosses than walls on more intensively managed farms.
The researchers also found that simple measures, such as the percentage of a wall covered, are reliable indicators of overall nature richness and could serve as a practical tool for assessing habitat quality. The findings show that lichens act as living records of human choices: how we farm doesn’t just shape crops and yields, but also the tiny, slow-growing lives with which we share the landscape. In the end, lichens can survive nearly everything – even long periods in outer space – but pollution will kill them.
In these muted days, when winter still holds a controlling hand, life persists in the smallest of places – the crevices and recesses of tree bark, the small hollows and indentations of gravestones and the furrows and folds of old stone walls.
