Umbrella Polypore
Polyporus umbellatus
Also called zhu ling, lumpy bracket (in part), many-capped polypore
A large branched cluster bearing dozens of small circular grey-brown caps, each with its own central stalk, growing from an underground tuber near hardwood roots.
Overview
Polyporus umbellatus is one of the most architecturally elegant polypores. Rather than a shelf or a hoof, it produces a repeatedly branched white stalk system that terminates in dozens — sometimes over a hundred — of small, circular, centrally stalked caps, giving a domed cluster that can reach 50 cm across and resemble a bouquet of tiny umbrellas.
The species is unusual in arising from a persistent underground sclerotium, a hard, irregular, blackish tuber that stores nutrients between fruitings and allows the fungus to reappear in the same spot over many years. This subterranean structure is why the fruiting body seems to emerge from bare soil rather than from visible wood.
It has been treated in the segregate genus Dendropolyporus by some authors, reflecting how different it is from the simple, single-capped Polyporus species. Widespread but never abundant in temperate Europe, Asia and eastern North America, it is a species that many field mycologists encounter only a handful of times.
How to identify it
Cap
Each individual cap is small — 1–4 cm across — circular to slightly funnel-shaped with a shallow central depression, and thin-fleshed. The surface is smooth to finely scaly or streaked, dry, and coloured pale grey-brown, tan or smoky brown, usually darker at the centre. Dozens of these caps are borne on a shared, repeatedly branched stalk system, and together they form a rounded, cauliflower-like mass 15–50 cm wide.
Pores
The pore surface is white to cream and runs conspicuously down the stalk of each cap (decurrent). Pores are small, round to angular, roughly 1–3 per millimetre, larger and more angular near the stalk. The whole underside remains pale even in mature clusters.
Stipe
Each cap has a genuine central stipe, and these merge downward into progressively thicker white branches that converge on a single thick base. The base connects to a hard, irregular, blackish underground sclerotium the size of a fist or larger, which is the fungus's perennial storage organ.
Flesh & spore print
The context is white, firm and slightly fibrous, thin in the caps and tougher in the branches. It does not change colour when cut. The spore deposit is white.
Where and when it grows
Umbrella Polypore fruits on the ground, typically within a metre or two of the base of a hardwood stump or a living tree, arising from buried roots or from its own sclerotium. Oak, beech, maple, birch and elm are the trees most commonly associated with it, and it favours mature deciduous woodland with deep leaf litter and moist soil.
It occurs across temperate Europe, through China, Japan and Korea, and in eastern North America, being generally scarce and patchily distributed everywhere. Fruiting takes place from midsummer into early autumn, often after prolonged rain, and because the sclerotium persists underground, the same site may produce a cluster in several successive years or after gaps of a season or two.
Ecological role
The fungus is a saprotroph and weak parasite of hardwood roots and buried wood, causing a white rot in which lignin and cellulose are both degraded and the residual wood becomes pale, soft and stringy. Most of its biomass is below ground in the root zone, with the sclerotium acting as a long-term energy reserve that funds the sudden production of a very large fruiting body.
That sclerotial strategy is uncommon among polypores and gives the species an advantage where fruiting conditions are unreliable: it can wait through poor years and then produce a substantial cluster in one flush. The fungus contributes to root and stump decay in mature deciduous woodland, and in doing so gradually converts buried woody material into soil organic matter.
Similar species
Grifola frondosa forms clusters of comparable size at the base of oaks, but its caps are grey-brown, fan- or tongue-shaped and laterally attached to flattened branches — never circular with a central stalk. That single feature, a round cap sitting on top of its own stem, is the fastest separator.
Meripilus sumstinei and Bondarzewia berkeleyi also form large basal rosettes: the first has grey-brown fans and a pore surface that bruises black, the second has thick, tough cream-tan fans with coarse, large angular pores. Polyporus tuberaster shares the underground sclerotium and central stalk but produces a single scaly cap rather than a branched multi-capped cluster, and Albatrellus species have single centrally stalked caps without a branching system.