Stems have trichomes from the bud rubbed off on them so they can get you high, however in comparison to the bud or even the leaves they are far less potent. Personally I think the best way to get the most of them is not to seperate them or the leaves from the bud, but to just cut them (and the leaves) up into very small pieces and mix them in with the bud when you're preparing it for a joint/pipe/bong/edibles.