Andricus grossulariae f. agamic

The asexual galls are formed on the buds, catkins or acorn cups of native oaks.  The galls have radiating blunt spines, green and sticky at first, then turning red and finally brown.  They are multi-chambered, and up to 3cm in diameter on terminal or lateral buds, smaller when formed on catkins and acorn cups.  Later on in the year, fallen galls may be found on the ground beneath oaks.

Andricus quercuscalicis (the Knopper Gall) forms similar asexual galls on acorn cups, but with a single larval chamber in inner gall.  Andricus lucidus, the Hedgehog Gall, is similar, but (as of autumn 2024) there are no confirmed records for these galls in VC55

Photograph the gall on oak, and note the host species

Native oaks

First recorded in Berkshire in 2000; spreading northwards (British Plant Galls, Redfern & Shirley, 2023)

occasional

See British Plant Galls (Redfern & Shirley, 2023)