To make a lovely, mildly fragrant tea, reminiscent of mint, dry the leaves or flowers in a warm oven for 30 minutes. Put 6 or more broken leaves or flowers in a heated teapot and pour on 1 cup of freshly boiling water. Cover the pot and keep it hot while the leaves steep for 5 minutes, then strain into a heated cup.
A few grains of sugar help to bring out the flavour rather than sweeten it, but milk would not be a good addition. Named for the Oswego district of New York State where the plant is quite common.