Plant Galls
Somerset's Plant Galls
Plant galls are distinctive, abnormal growths or swellings that manifest on various parts of plants, including leaves, twigs, roots or flowers. The morphology of galls is remarkably diverse, ranging from simple balls, knobs, lumps or warts to more intricate and complex shapes. The formation process of a gall is a sophisticated biological interaction. It commences when a gall-inducing organism attacks or penetrates the plant’s meristematic (growing) tissues. This biological intervention triggers the host plant to undergo a profound reorganization of its cells, leading to the development of the abnormal growth that subsequently encapsulates the gall-inducer.
Gall hotspots
Certain plant genera are particularly rich in gall diversity, serving as “gall hotspots”. Oaks are prime examples, known to host over 500 different gall-inducing wasps, aphids, mites and midges in the UK. Knopper Gall (Acorn Gall) Andricus quercuscalicis became established in Britain during the 1970s and is now widespread. Other Oak galls include Oak Artichoke Gall Andricus fecundator and the wonderful Silk Button Gall Neuroterus numismalis.
Plant galls of many shapes ...
Willows (genus Salix) are also notable for their abundance of associated galls. Many willows have galls caused by Sawflies (Euura species); these appear as bright red “beans” on the leaves. Robin’s Pincushion Diplolepis rosae is common and conspicuous gall forming mossy spheres along the stems of wild dog roses. Brambles can host the wasp gall Diastrophus rubi. One of the most frequently found galls is that caused by the fly Uophora cardui on Creeping Thistle. This causes a swelling on the stem of the thistle.
... and sizes
Rushes Juncus articulatus develop Tassel Galls caused by Livia juncorum. Searching Bracken will often result in the discovery of the Bracken Gall Chirosa grossicaud. A subtle fly gall causing a small leaf roll at the tip of the pinnule (main image).
Recording plant galls
Plant galls are fascinating structures found on nearly every tree, shrub, herb, flower and grass. The Somerset wetlands and surrounding areas have a rich diversity of plants and therefore plant galls. Join us and help find and record these amazing growths.