Country diary: Brontosaurian, Dalí-like trees that come with a warning

This is part of what is allegedly the deepest gorge in the world. At its bottom, should you complete the steep descent from Vikos village, you reach the River Voidomatis, which suddenly arises from springs in its otherwise dry Jurassic limestone bed. Later, it joins the Aoös to form one of the most pure freshwater systems in Europe.

At Vikos this manifests itself in deep, ice-cold water that is so translucent, yet so aquamarine blue, you’d think that it had been chemically manipulated. The wave-softened boulders look as if they have been positioned for bathing water nymphs, and through the sun-glazed leaves of oriental plane trees comes an intoxicating mix of piercing light with nightingale song.

Amid all the butterflies and flowers, to cap a sense of astonishing natural abundance, there is a seethe of insects that catch in the dappled light, creating a scintillating counterflow above the laminar sheen of the river. It is without doubt one of the most idyllic places that I’ve ever visited.

The organism that makes it special is the double line of oriental plane trees. They march slowly, in almost perfect step, down both banks, all the way through Zagori. They are astonishing beasts, with brontosaurian limbs and vast canopies. Yet these trees, which are made largely of water, also look like liquid. Their basal trunks have a curiously molten quality and they ooze like slow-setting lava directly into the shallows. Many are hollow. Yet they persist in these magical Dalí-like shapes for centuries – one local giant, “Ali Pasha’s plane”, is 700 years old – and in turn they stabilise and hold this habitat like a great sheltering wooden brace.

Alas for us all, there’s a serpent in paradise: a fungus, Ceratocystis platani, imported on ammunition boxes brought by American troops during the second word war. In eight decades, this human-borne predator has devoured many of the most iconic planes of France and Italy, and has arrived now in Greece. Those reading this on the banks of the Thames shouldn’t imagine that here is a faraway country of which we know little. London’s famous hybrid planes may be as susceptible to this blight as the magnificent trees of Vikos.

• Country Diary is on Twitter at @gdncountrydiary