The porcini mushroom defies farming and once had a Swedish king as fan
Porcini, ceps, penny buns: one prized mushroom with dozens of names, from squirrel's bread in Dutch to belly in Mexican Spanish. It can grow a cap wider than a dinner plate, yet it is very hard to cultivate, because it lives in partnership with the roots of living trees.
Boletus edulis is a bolete, meaning the underside of its cap carries spongy tubes instead of gills; spores escape through tiny pores, about two or three per millimetre. When young, those pores look stuffed with cotton, actually fungal threads, and they age from white to yellow and greenish. The stem is stout and thick relative to the cap and partly covered in a raised net pattern. The flesh is white and firm and hardly changes colour when cut.
The fungus wraps sheaths of tissue around tree roots in both broadleaf and conifer forests, a symbiosis called ectomycorrhiza, which is why farming it is so difficult. It is native across Eurasia and North America and has been introduced to the Southern Hemisphere. Typical caps reach 30 centimetres, and a giant found on the Isle of Skye in 1995 weighed 3.2 kilograms with a cap 42 centimetres wide. A large, darker Californian variant was formally identified only in 2007.
Names reveal how people saw it. The Italian porcino, little pig, echoes a Roman term for hog mushrooms, credited either to the resemblance of young caps to piglets or to pigs' appetite for them. German Steinpilz, stone mushroom, praises its firm flesh; English penny bun describes its round brown top. In Sweden it is Karljohanssvamp, after the French-born King Charles XIV John, who popularised it after 1818 and grew it around Rosersberg Palace.
Pierre Bulliard named the species in 1782, and the name has never changed. Cooks prize it in soups, pasta and risotto. It is low in fat and high in protein and fibre, and unusually for a mushroom it keeps its flavour when dried, which is how most of the autumn harvest from Europe and Russia travels the world. It is also one of the few fungi sold pickled.
Source: Boletus edulis
