If you’re out walking through parks and woodlands this month, keep an eye out for these strange-looking growths on the cones of Alder trees (Alnus glutinosa). They’re caused by the fungus Taphrina alni (also known as Taphrina amentorum), common name Alder tongue, a plant pathogen that uses chemicals to persuade the trees to produce these weird and wonderful tongue-shaped galls.

Though common in Western Europe, Alder tongue only appeared in Britain in the 1940s but has now become quite common throughout the isles as spores produced by the ‘tongues’ are easily carried on the wind to other trees. Sometimes the Alder cones have just one tongue, sometimes they have several, usually all emerging from the same spot on the cone and often curling into intriguing shapes (spot the dragons in the images below!). The tongues start off green in colour but then vary from yellow and orange to pink and red (which really would look very tongue-like) before becoming brown and black as they age. They can, in fact, be seen on Alder trees throughout the year, though, for some reason, I’m seeing more of them now, in the autumn months.