Nettles (Urtica dioica) are a common Eurasian weed that has now spread throughout the Northern Hemisphere. They’re notorious for their stinging hairs, which have a brittle silicate tip and a gland that supplies a cocktail of irritant chemicals, including histamine, for injection when skin meets needle. The hairs can be disarmed by a quick blanch in boiling water, which releases and dilutes the chemicals. But the harvest and washing require protective gloves. Nettles are made into soup, stewed, and mixed with cheese to stuff pasta.