Galls in gardens
By Peter Shirley British Plant Gall Society reviewed by Steve Head
Many garden plants are hosts to gall-causing insects, mites and fungi. Their galls are often complex and colourful and often harmless, although some can be serious pests of fruit and vegetables. Many can easily be identified (see references and images below) and learning to find and recognise them opens up a new dimension for wildlife gardeners.
The main groups of mite and insect gall-causers are eriophyid mites, gall midges
and gall wasps
. Other insect gall causers include some psyllids
, flies other than midges, beetles
. Galls are found on trees and shrubs and on many herbaceous plants, including grasses and ferns. They come in a wide variety of forms and sizes and may be very prominent or very obscure. Many are virtually hidden inside shoots, branches and flower stems. Insect and mite causers are wholly or partly enclosed by their galls, which provide them with nutrition as well as shelter and protection.
Most gall-causers are associated with particular species or genera of host plants. Well known examples include oak apples, robin’s pincushions on wild roses, nail galls on maples, limes and other trees, and red bean galls on willows and sallows.
The number of species and their range in Britain is constantly changing, not least because of the horticultural trade. A recently introduced psyllid Trioza alacris producing galls on bay has been spreading north, and a mite on Fuschia, Aculops fuchsiae first recorded at Kew in 2007, may be establishing itself in southern Britain. These and eight other galls likely to be found in gardens and allotments are described and illustrated below. Members are invited to report their presence to Peter Shirley (firstname.lastname@example.org). Records of other galls in gardens will also be welcome, and following verification they will contribute to The British Plant Gall Society’s expanding database of gall records.
Gall made by a fungus
Taphrina padi "tongue gall" fungus on Prunus species
There are two galled and two nomal fruits.