Atreasured old guide to wildflowers, a birthday gift 60 years ago, sits, dog-eared, on my bookshelf. It warns of poisonous plants with a bold, black letter P, in the kind of gothic typeface usually seen when the credits roll in a Hammer House of Horror movie. Botany with a frisson of danger, plants with a chilling story to tell. Few are deadlier than yew, fatal to cattle and horses if they browse its foliage, a favourite with assassins and still an occasional accidental killer of unwary people. The lethal dose is small, there’s no antidote, and death inevitably follows swiftly from heart failure. Add the tree’s ancient, funereal association with churchyards and you have all the elements of a gothic horror story. Every part of the tree contains the toxic alkaloid taxine, except for the watery, gelatinous red cups surrounding each seed; botanically they’re called arils but my grandmother in Sussex, who gave me the flower guidebook, knew them as “snotty-gogs”. Today, along the Teesdale Way, as I climbed over a stile under a yew tree, I caught the briefest of glimpses of a nuthatch: slate-grey back, apricot belly, a masked bandit with a black eye stripe and dagger beak. Unusually, for this habitual tree-dweller, it rose from the ground. A fallen log was spattered with patches of brilliant crimson jelly. This was where the bird had separated yew seeds from their gooey cup, then carried them away to wedge in a bark crevice, chisel open and extract the kernel. I could hear it hammering, somewhere high above my head. Redwings swallow yew berries whole, only digesting that soft red cup. The toxic, hard-coated seeds pass through the birds’ guts unharmed and their droppings leave a trail of germinating seedlings. Such is the evolutionary bargain struck between plant food-provider and avian tree-planter. Nuthatches, destroyers of yew seeds, must have evolved a gut capable of detoxifying a poison that can paralyse hearts: advantage nuthatch. But pollination conditions must have been good this summer. The tree was truly festive with red-cupped seeds. It could afford the loss. Meanwhile, flocks of redwings have been pouring into the dale from Scandinavia. The nuthatch’s window of opportunity might not last long.