I’m a proud member of Happy (the Hitchin association of pavement plant yokels), so-called by my friend Phil, a fellow wildflower enthusiast. You’ll find us roaming the town centre, scanning brick walls and peering into paving crevices on the hunt for the tenacious species that thrive in these oft-overlooked habitats. I had my pavement epiphany a couple of years ago outside the chemist on Hitchin high street when I saw a little lass bending down, scrutinising the paving stones. Her dad soon whisked her away and I went over to look. She’d noticed a community of self-seeded plants growing in a semicircular crack. The diversity of the miniature garden astonished me: mosses, meadow grass, goosegrass, common whitlowgrass, sow thistle, fleabane, and there, among the annual plants and perennial cigarette butts, a seedling with trilobed leaves – a Hitchin speciality – rue-leaved saxifrage (Saxifraga tridactylites).
Now it’s early May and this three-fingered rock-breaker’s tiny white flowers have opened in the sun, the foliage blushing redder the drier and sunnier its location. Looking closely, you can see sticky hairs lining the fleshy leaves and stems – but be prepared for funny looks if you lie prostrate on the pavement to examine this low-growing annual.
Surprisingly for a plant that naturally grows on limestone cliffs and sand dunes, the first UK record was from Chancery Lane in 1597. Once rue-leaved saxifrage had infiltrated street cracks and wall crannies, it developed a reputation for urban persistence that seems to be borne out locally – I recently tracked down a record of “rue-leaved sengreen or whitlow grass” (an old name) from May 1811 and an herbarium specimen collected from a wall in Hitchin in April 1841.
One spring, thousands of plants appeared on the roof above the local Sally Army shop. This year though, the summit-scaler has reinvented itself as a river-rider, flowing along the bricked banks of the Hiz, pooling between treads and risers in the steps by the pond, leaving a ruddy flush in its wake. Yet hardly anyone sees it. If it weren’t for the odd inquisitive youngster and a few Happy townsfolk, I’m sure rue-leaved saxifrage would go about its annual business unnoticed for many centuries to come.
• Nic’s book Land Beneath the Waves is out on 12 June
• Under the Changing Skies: The Best of the Guardian’s Country Diary, 2018-2024 is published by Guardian Faber; order at guardianbookshop.com and get a 15% discount
