Rigidoporus ulmarius

(Sowerby) Imazeki

A mature fruiting body growing from an old wound at 3m up on a hybrid black poplar in Basildon, Essex.
Growing from within a basal cavity on horse chestnut at Greenwich Park, London
On a pruning wound 3m up a mature horse chestnut in Runnymede, Surrey
A mature fruiting body within algal staining at the base of a mature aspen in Hockley, Essex
The white flesh and cinnamon tube layer from a bracket on beech in the New Forest, Hampshire

A mature fruiting body growing from an old wound at 3m up on a hybrid black poplar in Basildon, Essex.
Growing from within a basal cavity on horse chestnut at Greenwich Park, London
On a pruning wound 3m up a mature horse chestnut in Runnymede, Surrey
A mature fruiting body within algal staining at the base of a mature aspen in Hockley, Essex
The white flesh and cinnamon tube layer from a bracket on beech in the New Forest, Hampshire
Cross section showing the white flesh and cinnamon-coloured tube layer.
Cross section showing the white flesh and cinnamon-coloured tube layer.
Developing bracket on poplar in Laindon, UK.
Mature bracket showing white spore beneath on chestnut at Wimpole House, UK.
Mature algal-greened bracket on chestnut in Iver, UK.

Common name

Giant elm bracket.

Often found on

Beech, horse chestnut, poplar.

Sometimes found on

Elderberry, elm, lime, maple, plane, sycamore.

Location

Found at the base of the tree and along the main stem – when found up the stem, it often emerges from pruning wounds or storm-damaged regions where limbs have been lost. Can be found growing within hollows quite routinely.

Description

Perennial. Tough and woody. Begins as a white mass. Develops into a bracket with a beige-white upper surface that routinely becomes algal-stained and mossy. Pore layer off-white. Spore white. Flesh strikingly white. Shallow tube layer cinnamon-orange. Can become very large.

Confused with

Oxyporus populinus (deep tube layers); Perenniporia fraxinea (flesh is not white).

Significance

Attributed to a brown rot of the (false) heartwood. Reaction growth therefore not induced (wood retains its rigidity). Potentially weakly pathogenic though research is lacking. When fruiting from a pruning wound or area that has been storm-damaged, decay may be localised. For trees where targets exist, investigations into hollowness may be required. Where decay is suspected to be below-ground, stability investigations may be needed.