Away across the valley, the cliffs of Cronkley Scar rise up, a sombre grey wall of dolerite columns. We cross the Tees by Cronkley Bridge, the river running low in this dry spring. Then it’s up through a forest of twisted junipers – the largest area of this native conifer in England – and across the moor to join the Green Trod. This ancient drover’s road is a wide green band that climbs up to Cronkley Fell in the Moor House-Upper Teesdale national nature reserve. To botanists these names, along with Widdybank Fell and Cow Green to the west, hold a kind of magic. As the path gains height it fragments into a mass of boulders. Grouse retreat into the heather telling us to “go back, go back”. On the flat exposed hilltop is the first of several exclosures fenced against grazing. We edge round it, using binoculars to spot treasures growing among straw-coloured grasses. There are tiny bird’s-eye primroses, Primula farinosa, their heart-shaped petals a startling sugar pink. Emerald leaves of twayblade grow alongside those of mountain everlasting, Antennaria dioica, with their furry white undersides. And there – the plants I’d most hoped to see, startling in their blue intensity, the most celebrated of the “ice flowers”, a cluster of spring gentians, Gentiana verna. Their buds are beautiful too, dark blue like tightly furled umbrellas. These rarities, growing on the sugar limestone of the hilltop, are part of the Teesdale assemblage, plants considered to have survived continuously since the last ice age. Surveying them has been the life work of the eminent botanist Dr Margaret Bradshaw. Shocked by the declines she has recorded, she formed the Teesdale Special Flora Research and Conservation Trust. Last year, at the age of 95, Margaret trekked 88km on her pony, Sigma, to raise funds for her charity; she learned to ride two years before and is still riding. This year the spring gentians are flowering earlier. Botanists predicted this would happen in a changing climate. The trust’s mission to survey and protect these arctic-alpine plants is urgent. I feel grateful for my day in the hills and the singing blue of the gentians.