Depressed Hedgehog

The Depressed Hedgehog is the slender, bog-dwelling member of the genus Hydnum, a group whose members hang their spores on downward-pointing spines rather than on gills, pores or ridges. Rub a finger across the underside and the fine teeth crumble away — a texture nothing else in the woods quite matches.

The species takes its name from the neat navel-like depression at the centre of its cap, which is usually much more sharply defined than the broad shallow dip seen in its larger relatives. Combined with its small size, slender stalk and preference for sphagnum and moss beds under conifers, this makes it one of the more easily placed hedgehog fungi.

Despite the spiny underside, Hydnum is not closely related to the crust-like or bracket-forming toothed fungi. Molecular work places it firmly beside the chanterelles in the order Cantharellales, so the Depressed Hedgehog is, in evolutionary terms, a chanterelle relative that grows teeth instead of ridges.

Cap

The cap is 1–5 cm across, convex at first and soon developing a distinct, often abrupt navel-like depression at the centre; in age the whole cap may become shallowly funnel-shaped. The surface is dry, smooth to minutely felted or suede-like, and coloured pale orange, orange-tan, apricot or buff-brown, usually fading toward the margin. The edge is thin, often wavy or lobed.

Teeth

The underside is covered in crowded, slender, brittle spines 2–6 mm long that taper to fine points and break off easily. They are white to pale cream or buff when young, darkening to pale orange-brown with age, and they run a short way down the stalk.

Stipe

The stalk is 3–7 cm long and 3–10 mm thick, slender, cylindrical or slightly swollen toward the base, often central but sometimes off-centre. It is whitish to pale orange and discolours to brownish-orange where handled or bruised.

Flesh & spore print

The flesh is white, brittle and rather crumbly, and slowly stains orange-brown to rusty where cut or bruised. The odour is mild. The spore print is white.

This fungus fruits on the ground in damp coniferous and mixed forest, and is strongly associated with sphagnum bogs, feather-moss carpets and mossy hollows. It also appears in wet mixed woodland with hemlock, spruce and birch, usually where the moss layer is deep and continuously moist. Fruit bodies grow scattered or in small groups, and slender stalks are often buried to half their length in the moss.

The season runs from late summer into autumn, peaking after sustained wet weather. It is chiefly a northern species in North America, common across the boreal and northeastern forest belt and in montane conifer stands further south, with similar small navel-capped hedgehogs recorded in northern Europe and Asia.

The Depressed Hedgehog is ectomycorrhizal, forming sheathed root tips on conifers and, in mixed stands, on birch and other broadleaf trees. Its hyphae thread through moss and peat, capturing nitrogen and phosphorus from acidic, nutrient-poor organic layers and passing them to its host in exchange for photosynthetic sugars.

In boggy and mossy forests where decomposition is slow and mineral nutrients are scarce, mycorrhizal fungi of this kind are essential to conifer growth. The brittle spines shed spores downward into the sheltered air layer beneath the cap, from where they are carried off by air movement, and the fruit bodies are readily consumed by slugs and fungus-feeding insects that carry spores further afield.

The Hedgehog Mushroom (Hydnum repandum) is much larger and stouter, with a thick irregular cap that is at most broadly and shallowly depressed rather than sharply navel-like, a thick stalk, and paler cream to buff colouring. Hydnum rufescens is closer in size and orange colour but its cap lacks a pronounced central navel and its spines are typically not decurrent. Hydnum albidum is whitish overall and bruises yellowish-orange.

Among unrelated fungi, small orange Cantharellus species can look similar from above, but their undersides carry blunt forking ridges rather than free-hanging brittle spines — the single most reliable separation.