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My route along Teesdale is full of distractions. I stop twice, awed by the sight of 30 black grouse in a field, then to watch displaying peewits, tumbling and diving with sweet, airy calls. This is the heart of the North Pennines national landscape (NPNL), and its visitor centre at Bowlees is in a 19th-century Methodist chapel. The Bow Lee beck runs close by, winding through a wooded dene, then dropping down Summerhill Force, the pretty waterfall camouflaging Gibson’s Cave.

A small limestone quarry by the beck resounds to the cascading songs of chaffinches, spring warmth held within its rocky bowl. The ledges of these cliffs, inaccessible to sheep and rabbits, have been chosen for the planting of a rare native tree, the rock whitebeam, Sorbus rupicola. Seed was collected in autumn 2022 from a craggy site by the fast-flowing Tees, carefully packed, and sent to the Millennium Seed Bank managed by Kew Gardens. Further seed was germinated in the small wildflower nursery at Bowlees so that rock whitebeam could be re-established in Teesdale.

This shrubby tree, with its white-backed leaves and large rowan-like fruits, is found in only a few locations across the UK. Collecting seed from the riverside outcrop was challenging; extracting it from the jammy, sticky fruit was laborious. Now, Will and Adam from NPNL carry a ladder and the pot-grown trees to the quarry face, identifying a possible planting spot five metres up the wall.

They work the compost from the fine reddish roots before Adam carries the young trees in a bag up the ladder, searching for nooks where the trees might successfully establish. Feeling with his hands for sparse pockets of soil, he gropes for enough depth in the settled leaf litter. “There’s even a worm up here,” he calls down. Water drips slowly through moss, among herb robert and nettles; it’s wet but draining. Some of the trees go in here, some on a sunny ledge for comparison, where the thorny arch of a dog rose should protect the trees from rabbits. Rock whitebeam clings on where other trees would struggle, long-lived but vulnerable to grazing. Sending its roots between rock crevices, surviving in harsh conditions, this is truly a plant that lives on the edge.

• Under the Changing Skies: The Best of the Guardian’s Country Diary, 2018-2024, is available now at guardianbookshop.com
• Susie’s new book, Nature’s Almanac: A Gift for Every Day of the Year, is out now, published by Saraband