I had come to this woodland on the steep banks of the River Tees, downstream from Abbey Bridge, in search of an unusual form of wood sorrel (Oxalis acetosella) that I last found here four years ago.
The typical flowers of this demure woodlander are outwardly pure white, with yellow spots inside at their base and delicate lilac veins radiating towards their edges. This mutant’s petals were a startling shade of purple.
It takes just a few minutes’ walk through this wooded gorge to realise why new tree plantations can never mitigate loss of ancient woodland. The ground flora here has the kind of complexity that takes centuries to develop. There are vast swathes of overlapping tongue-shaped leaves of ramsons and snow-white drifts of wood anemones, with their filigree leaves as intricately interlaced as a William Morris wallpaper pattern. Among these, cuckoo-pint, sweet woodruff and dog-violet, shield fern, bluebell and red campion; fresh new foliage covering what was until a few weeks ago a deep layer of last autumn’s fallen oak and sycamore leaves.
Miraculously, in this springtime race to bloom, attract a pollinator and set seed before the tree canopy casts deep shadow, the little purple patch of wood sorrel, with its shamrock-shaped leaves that fold down like a triangular tent during rain or when darkness falls, had persisted.
Wood sorrel flowers attract few pollinating insects, and the purple-flowered plant seemed to be no exception. But for all its apparent vulnerability, this tenacious species has a trick for reducing the need for them: additional cleistogamous flowers, which remain as closed buds, self-pollinating and setting seeds unaided.
It has another important survival strategy, linked to the decay of surrounding mature trees in old woodlands. Its slender rhizomes creep under the blankets of moss that cover fallen dead trunks and branches, as they slowly moulder into the soil. The purple wood sorrel has taken advantage of one such platform, raising it above the surrounding carpet of woodland plants that threaten to smother it.
I imagine it will survive here until its decaying log finally crumbles into the soil, and it drowns under ramsons foliage, unless another dead branch falls within reach of its rhizomes, and rescues it.