Galls are manifestations of anomalous growth in plant tissues as a reaction to the chemical stimulus produced by a gall forming organism. The most peculiar and interesting galls are induced by insects (Diptera, Hymenoptera, Rhyncota, Coleoptera) on the Angiosperms, particularly within the Fagaceae family.

The plant’s growth pattern becomes adapted to the needs of the gall forming insect, causing the plant to produce gall tissues that enclose the grubs: they feed on a nutritious layer of cells within the gall and, protected inside their sheltered haven, turn into adult insects.

I have been studying galls for years, searching for them through the branches and leaves of many species of trees in northwestern Italy, where I live.

My watercolours on vellum dedicated to galls were awarded an RHS Gold Medal and Best in Show Award in 2006.

Andricus caputmedusae gallAndricus caputmedusae gall
Andricus coriarus gallAndricus coriarus gall
Baizongia pistaciae gallsBaizongia pistaciae galls
Dryomyia circinnans gallsDryomyia circinnans galls
Galls on Populus nigra leavesGalls on Populus nigra leaves
Eriosoma pyricola gallEriosoma pyricola gall
Cynips mitrata gallsCynips mitrata galls
Andricus hartigi gallAndricus hartigi gall
Rosa hybr with Diplolepis rosae gallsRosa hybr with Diplolepis rosae galls
Cynips cornifex gallsCynips cornifex galls
Eriosoma lanuginosum gallEriosoma lanuginosum gall
Eriosoma lanuginosumEriosoma lanuginosum
Three galls (Andricus quercustozae)Three galls (Andricus quercustozae)
Dasineura heterobia gallDasineura heterobia gall

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See also my Autumn Walks