Boletus rex-veris — Spring king bolete

Left image: Spring king bolete2. Right image: Pores at higher magnification. Photographs by Paul Kroeger.

Odour: Mild, pleasant.
Cap: 10–30 cm in diameter, broadly convex to almost flat. The colour is commonly reddish brown but it can also be dark brown, or more ochre-coloured when in sunlight, or paler when the cap is covered by soil. Surface may be dry or wet/slimy if weather is moist, smooth. Like the king bolete, the spring king may be partly buried in duff, looking like a bakery bun emerging from leaf litter.
Pores: On the under surface of the cap find minute pores. Pore surface is white when young and pores are stuffed with whitish cottony tissue; pores open and become yellowish with age. The pore surface does not change to blue when rubbed.
Stem: 5–20 cm long x 2.5–10 cm wide, bulbous when young, later more cylindrical, often with a tapering or pointed base. Surface white when young, to tan or pinkish coloured in upper half with age. With a fine white network of slightly raised ridges on the top half of the stem. Flesh in cap and stem white and firm.
Ring or veil: None.
Cup: None.
Spores: 14–18 x 4–5 µm, smooth, without a germ pore.
Habitat: In small groups on the ground, with pine (Pinus) and red fir (Abies magnifica). However, the specimen shown here grew in woodchips, under red oaks (Quercus rubra) on the coastal University of British Columbia campus in Vancouver, BC; ectomycorrhizal.
Geographic distribution1: In the western North American mountains from BC southwards into the Sierra Nevada in California, and east to Idaho. The species was only described in 2008; hence the extent of its geographical distribution is still being discovered.

Rule out poisonous species before eating a mushroom with a 'bakery bun' cap shape. Look closely to make sure the underside of the cap is covered with tiny pores. Poisonous Cortinarius species with a similar shape and colour will have radiating, linear gills rather than pores. Check that the top third of the stem is covered by white, net-like raised ridges just visible with the naked eye. Boletus rex-veris has light tan to yellowish pores, and pores and stem do not become blue where rubbed. Several poisonous species including Neoboletus erythropus and Rubroboletus eastwoodiae (growing with oaks) are similar BUT they have orange or red pores that usually change to blue/black within ~10 min of being rubbed. The Spring king bolete has a mild, non-bitter flavour; bitter-tasting boletes are inedible.

Other Boletus species look very similar. All Boletus species with a brown cap and a light stem with a network on it (sometimes subtle), and no colour changes to red or blue when cut or with age are considered good edibles.

Illnesses from eating the spring king bolete have yet to be reported. However, in a few rare people with unusual sensitivities, eating the spring king will probably cause upset stomachs, vomiting, and diarrhoea; the same spectrum of symptoms that result from eating the closely related Boletus edulis5.

Treatment: Contact your regional Poison Control Centre if you or someone you know is ill after eating boletes. Poison centres provide free, expert medical advice 24 hours a day, seven days a week. If possible, save the mushrooms or some of the leftover food containing the mushrooms to help confirm identification.

Poison Control:
British Columbia: 604-682-5050 or 1-800-567-8911.
United States (WA, OR, ID): 1-800-222-1222.

MyCoPortal. Mycology Collections Portal, <> accessed February 2018.

Specimen Boletus rex-veris UBC F30908, GenBank #MF955196.

Arora, D. California porcini: three new taxa, observations on their harvest, and the tragedy of no commons. Econ. Bot. 62, 356-375, doi:10.1007/s12231-008-9050-7 (2008).

Desjardin, D. E., Wood, M. G. & Stevens, F. A. California Mushrooms: The Comprehensive Identification Guide. Timber Press, Portland, Oregon (2015).

Beug, M. W. NAMA Toxicology Committee Report North American Mushroom Poisonings, <> accessed May 6, 2017.