Stems have been made with cedar - every B.N. Morris canoe I have seen has cedar stems. If you can get spruce to bend into the shape of a stem, you have a free ticket to the steam-benders hall of fame. (Note that it doesn't count if you laminate the stems, or split them into layers as in a birchbark canoe). Ash has the advantage of being easy to bend, is strong, and holds fasteners well. Perfectly good stems have also been made of white oak and red elm. Avoid red oak, it is very porous and rots quickly.
Cheers,
Dan