[header] How to make nettle tea [title] Gather young, spring nettles. [step] Plan your expedition in the spring, before they've flowered. Some think that nettles taste bitter and unpleasant after they've flowered. 
Others claim that cystoliths (microscopic stones) in the adult plants can irritate the urinary tract. Both of these claims are disputed by some nettle harvesters, but most stick to the young plants.