Spindleshank

Gymnopus fusipes, long known as Collybia fusipes, is the most robust of the toughshanks and the easiest to name once the stem is examined. Fruit bodies grow in dense tufts against the trunk bases, buttress roots and stumps of oak, and less often beech, returning to the same trees for many years.

The epithet fusipes means spindle-footed: the stem swells in its middle and tapers both upward and, more dramatically, downward into a long, twisted, root-like extension that runs to the tree's roots. The surface is deeply furrowed lengthwise, giving the stem a rope-like look.

It is one of the few Gymnopus species that is not purely a litter decomposer, since it invades and rots living root tissue before continuing on the dead wood.

Cap

The cap is 3-9 cm across, convex then flattening, often with a broad umbo and a wavy margin. The surface is dry and tough, reddish brown to tan or chestnut, drying paler and very frequently developing darker reddish-brown blotches and spots with age.

Gills

Gills are broad and widely spaced, whitish to pale buff, sometimes forking or joined by cross-veins, narrowly attached with a slight decurrent tooth, and characteristically spotting rust or reddish brown as they mature.

Stipe

The stem is 4-10 cm long, thickest in the middle and tapering both ways, deeply grooved and twisted lengthwise, reddish brown and darker downward, extremely tough and cartilaginous, prolonged below into a long rooting base. Stems in a tuft are usually fused at the point where they enter the wood.

Flesh and spore print

The flesh is white, very tough and fibrous, unchanging when cut. The spore print is white.

Spindleshank is found in dense clumps at the base of living oak trunks, on exposed buttress roots, and on oak stumps; beech and occasionally other broadleaves also host it. It is a woodland, parkland and hedgerow species that reappears in the same spots year after year.

The season is long, from early summer through autumn, earlier than most woodland agarics. It is widespread across Europe and reported from temperate Asia and North America wherever suitable oaks grow.

The fungus behaves as a weak parasite and root pathogen, colonising the structural roots and root collar of oaks and causing a slow white rot. Infected trees may show thinning crowns over many years, though the fungus is generally slow-acting and often associated with trees already under stress.

After host tissue dies it continues as a saprotroph on the same wood, which is why tufts persist on stumps long after a tree has gone. The rooting stem base marks the connection between the fruit body and the buried infected root.

Armillaria mellea, which shares the trunk-base habitat and tufted habit, has a ring on the stem, black bootlace rhizomorphs under the bark and a cream spore print, and its gills do not develop the rusty spotting. Gymnopus peronatus is scattered in litter with a woolly stem base and no rooting spindle.

Rhodocollybia maculata has a whitish cap that spots rusty red like the gills, but its gills are very crowded, its stem is straight and only slightly rooting, and its spore print is pale pinkish. Hymenopellis radicata also roots deeply but is a solitary, slimy-capped mushroom with widely spaced white gills and a slender, non-grooved stem.