Ischnoderma resinosum

[ Basidiomycetes > Polyporales > Hapalopilaceae > Ischnoderma . . . ]

by Michael Kuo

This attractive and widely distributed polypore is easy to recognize--with close inspection. The young mushrooms are thick, soft, and fleshy--much softer than you might expect in a polypore, especially if, from a distance, you thought you were looking at Ganoderma applanatum. The young pore surface is whitish, but it turns brown very quickly when bruised. Ischnoderma resinosum has a tendency to grow not only on the sides of dead logs, but also on their undersides, where it produces a capless version (or extension) of itself that consists primarily of a pore surface (see the fourth illustration).

As Ischnoderma resinosum matures, it becomes very tough and leathery, and much more "polyporeish." Believe it or not, however, the fleshy young caps are not only edible, but quite good. The species is typically listed as "inedible" in field guides, but I suspect this is because authors have mature, leathery specimens in mind. I do not recommend this species for beginners, but if you are 100% sure of your identification Ischnoderma resinosum is well worth a culinary experiment. Try only a few bites the first time, however; fleshy polypores are notorious for causing "allergic reactions" (minor gastric distress) in some individuals. You will need to use only the soft edges of young fruiting bodies, and you should probably cook the mushrooms a little longer than usual, to soften them up.

Description:

Ecology: Alone or gregariously on fallen hardwood and conifer trunks and branches; sometimes in overlapping clusters; annual; saprobic; causing a whitish to yellowish rot that separates the annual rings in the wood and often smells of anise; appearing on recently fallen wood and on wood that has been down for many years, but not typically on well rotted wood; usually a fall species, in north-temperate regions; very widely distributed in North America.

Fruitbody: Up to 15+ cm across; irregularly bracket-shaped or kidney-shaped; broadly convex; when young quite thick and fleshy, with a pale brownish, finely velvety cap surface and a thick white margin that can be adorned with water droplets in wet weather; in maturity dark brown, sometimes with zones of color, fairly smooth, dry, tough and leathery or corky; without a stem.

Pore Surface: When young whitish, soft, promptly bruising brown; in maturity pale brown and hard; 4-6 angular or round pores per mm; tubes to 1 cm deep.

Flesh: Whitish and soft at first; darkening to brownish or cinnamon brown, and becoming tougher with maturity.

Chemical Reactions: All parts grayish to blackish with KOH.

Spore Print: White.

Microscopic Features: Spores 5-7 x 1.5-2 µ; smooth; cylindrical (if sectioning for spores, use the marginal area of young specimens); clamp connections present.

REFERENCES: (Fries) Karsten, 1879. (Overholts, 1953; Smith, Smith & Weber, 1981; Gilbertson & Ryvarden, 1986; Arora, 1986; Phillips, 1991/2005; Lincoff, 1992; Barron, 1999; Roody, 2003.) Herb. Kuo 09220407, 10070401.

Polyporus resinosus is a former name.

"Ischnoderma benzoinus" is recognized as a separate, conifers-only species by some authors (especially in Europe), who separate it from a hardwoods-only Ischnoderma resinosum on the basis of its putatively darker flesh. Culture studies refute this separation, however, and the reigning authoritative source on North American polypores (Gilbertson & Ryvarden, 1986) synonymizes the two species--as did the previous North American polypore "Bible" (Overholts, 1953).

Further Online Information:

Ischnoderma resinosum at Roger's Mushrooms
Ischnoderma resinosum at Fungi of Poland

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Cite this page as:

Kuo, M. (2004, October). Ischnoderma resinosum. Retrieved from the MushroomExpert.Com Web site: http://www.mushroomexpert.com/ischnoderma_resinosum.html