Worcestershire Record No. 4 May 1998 p.7


By Dan Puplett

The highly distinctive cotton-wool gall develops on the male catkins of oak trees. It is a fluffy mass of around 20-30 mm in diameter which, as the name suggests, resembles a ball of cotton-wool in appearance and texture. Caused by the uncommon cynipid wasp, Andricus quercusramuli, the structure actually conceals as many as 20 true galls, each containing a single larvae of the sexual generation. The pear-shaped galls of the asexual generation develop in the leaf-buds in late autumn, but are seldom recognised (Darlington 1975, Lewington & Streeter, 1994).

The first reported sighting of this gall in Worcestershire since 1978 was stumbled upon at Lower Smite Farm in late May. Keep an eye on pedunculate and sessile oaks for this striking and unusual growth which may be found during May and June (Connald, 1908).

Please send your records to John Meiklejohn at the Worcestershire BRC.


Connald, ET 1908. British Oak Galls. Adlard & Son: London.
Darlington, A 1975 (revised). The Pocket Encyclopaedia of Plant Galls. Blandford Press. Poole.
Lewington, R & Streeter, D 1993. The Natural History of an Oak Tree. Dorling Kindersley. London.

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