What You Should Know
Tuber gibbosum is a member of the Tuberales in the Discomycetes in the phylum Ascomycota. Most other Discomycetes have an epigeous (above ground) apothecium, an open ascocarp with the asci in a hymenium. However, the Tuberales have a hypogeous (below ground) ascocarp with scattered asci.
It is roughly round with a dirty stone-colored surface that becomes darker brown with age. It is smooth but furrowed and its translucent flesh is pale gray, marbled with white veins. Oregonense has an opaque whitish to yellowish or olivaceous peridium that develops prominent reddish-orange to cinnamon colors. The gleba initially is whitish, then becomes brownish with white marbling. The odor is complex and has been described as a mix of garlic, spices, cheese, and other indescribable components.
Tuber gibbosum is found in the Pacific Northwest region of the United States, where it grows in an ectomycorrhizal association with Douglas-fir. It is commercially collected between as early as October and into March.
Other names: Spring Oregon White Truffle.
Tuber gibbosum Related Species
There are a couple other species of Tuber in the Pacific Northwest, including the milder-tasting Tuber giganteum. The black truffle or Perigold truffle (Tuber melanosporum) grows primarily in Europe, especially Italy and France. In Italy, trained pigs hunt for truffles with their owners, while French hunters usually use dogs. There are various other genera of truffles and false truffles, including Gautieria, Elaphomyces, Geopora, Leucangium, and others. There are truffles and false truffles in all parts of the world, but not all species are edible. None are poisonous that we know of, but most don't have any real flavor.
Tuber gibbosum Taxonomy
The species was first described by American mycologist Harvey Wilson Harkness in 1899. The specific epithet derives from the Latin word gibbosum meaning "humped", and refers to the irregular lobes and humps on larger specimens. T. gibbosum is part of the gibbosum clade of the genus Tuber. Species in this clade have unusual "peculiar wall thickenings on hyphal tips emerging from the peridial surface at maturity."
T. gibbosum resembles the similar species T. oregonense, and both are found growing under Douglas fir.
Photo 1 - Author: Ryane Snow (snowman) (Creative Commons Attribution-Share Alike 3.0 Unported)
Photo 2 - Author: Daniel B. Wheeler (Tuberale) (Creative Commons Attribution-Share Alike 3.0 Unported)
Photo 3 - Author: Ryane Snow (snowman) (Creative Commons Attribution-Share Alike 3.0 Unported)
Photo 4 - Author: Daniel B. Wheeler (Tuberale) (Creative Commons Attribution-Share Alike 3.0 Unported)