Hardwood Trunk Rot

Description

Phellinus igniarius is a hard, woody bracket growing sideways out of a tree trunk, without a stem. It is hoof- or cushion-shaped, usually 5–25 cm wide, and its surface is grey to blackish, cracked and concentrically zoned; it may be green from algae. The underside consists of very fine, greyish-brown pores, and a cross-section shows rusty-brown, woody flesh and several layers of tubes.

It can be seen all year round, because the fruiting body is perennial and adds a new layer every season. You will most often find it on willows, but also on birches, alders, beeches, hornbeams and fruit trees, especially near water, in thickets and in orchards. In Poland it is very common. It causes white rot of wood and weakens the affected tree.

It is distinguished from the similar tinder fungus by its harder, darker flesh and firmer attachment to the trunk. The aspen bracket grows only on aspen, and the fir bracket mainly on firs. This is an inedible fungus, so there is no reason to collect it.

Identification features

Cap

Perennial, woody fruiting body without a stem (a stipe is present only in the juvenile stage); attached to the substrate by its side. Diameter usually 5–25 cm (exceptionally up to 40 cm), thickness 2–15 cm (exceptionally up to 20 cm). Shape at first bulbous, later flat, hoof-shaped or cushion-shaped. Surface grey, darkening with age to blackish, hard, often cracked, smooth or slightly suede-like, concentrically zoned, sometimes green from algae growing on it. Margin broad, rounded. A new layer grows each season; the fruiting body can have up to several dozen (about 80) annual growth rings.

Hymenophore (underside of the cap)

Poroid. Tubes arranged in many layers, each 2–7 mm long, the colour of the fruiting body or paler, dark brown. Pores very fine, round, greyish brown, 4–6 per mm. Old tube layers are often overgrown by younger ones, and unreleased spores are visible in cross-section as brown spots.

Stem

Absent (sessile fruiting body).

Flesh

Woody, zoned, from dark rusty brown to chestnut brown; hard, becoming even harder with age and dryness, softening in humidity. Smell distinctly mushroomy, taste bitter. The flesh turns black with KOH. Do not taste the flesh.

Spore print and spores

Spore print white to whitish. Spores colourless, 4–6.5 × 4–5.5 µm.

Habitat and distribution

Ecology. A tree-dwelling fungus causing white rot of wood (decomposition of lignin and cellulose). It attacks living hardwood trees, most often willows, also birches, alders, beeches, hornbeams and fruit trees. The rot weakens the wood, so woodpeckers readily excavate nest cavities in such places.

Distribution. North America, Europe, Asia and the Canary Islands. Very common in Poland, in the lowlands and lower mountain elevations: in riverside forests and thickets, along streams, in orchards, gardens and various forests. Not legally protected in Poland.

Fruiting. Perennial fruiting body (10–15 years or more), visible all year round; a new tube layer forms every year.

What can it be confused with?

• Fomes fomentarius (tinder fungus) — Flesh softer and paler, fruiting body less firmly attached to the trunk.
• Phellinus tremulae (aspen bracket) — Grows only on aspen.
• Phellinus hartigii (fir bracket) — Grows mainly on firs.
• Fulvifomes robiniae and species of the genus Fomitiporia — Similar perennial, woody fruiting bodies; telling them apart requires microscopic features and knowledge of the host.

Never rely on a single feature. If you are not sure — do not pick it; show the mushroom to a qualified mushroom expert.

Interesting facts

• The name “ogniowy” (‘of fire’; also huba ogniowa, żagiew ogniowa) comes from the fact that dried fruiting bodies cut into slices were formerly used as tinder for starting fires with a flint and steel.
• The fruiting body can be among the longest-lasting of any fungus: it can have as many as about 80 annual growth rings.
• The wood rot caused by this species makes it easier for woodpeckers to excavate nesting cavities.
• In Alaska, the ash from a burnt fruiting body (“punk ash”) is sometimes mixed with chewing tobacco to enhance the effect of the nicotine.