Alder tongue gall

Image: © Lairich Rig Taken: 24 Jul 2009

This gall, which affects the cone-like female catkins of the common (or native) alder (Alnus glutinosa), is caused by a species of fungus, Taphrina alni. The galls start off greenish, but redden as they age. Taphrina amentorum is sometimes encountered as an older synonym for T. alni. According to "British Plant Galls" (Redfern/Shirley/Bloxham), this gall was very rare in Britain in the 1940s, when it was known only from Cornwall. Even in recent years, it was not at all common; however, it now seems to be expanding its range rapidly. The gall shown here is 25mm long, larger than the catkin (15mm high) on which it is growing. This is just one of two locations (both alongside the River Leven) in which, on the day this photo was taken, I happened to notice these galls; about 800 metres upstream, another common alder tree was more densely galled, with up to half a dozen "tongues" per catkin: Image Over the next few weeks, I found that it was in evidence in several other locations along the course of the river; in fact, it now appears to be quite common in this area.

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