The Collaborative International Dictionary of English v.0.48:

Wampee \Wam*pee"\, n. (Bot.)
   (a) A tree (Cookia punctata) of the Orange family, growing
       in China and the East Indies; also, its fruit, which is
       about the size of a large grape, and has a hard rind and
       a peculiar flavor.
   (b) The pickerel weed. [Southern U. S.]
       [1913 Webster]

WordNet (r) 3.0 (2006):

wampee
    n 1: American plant having spikes of blue flowers and growing in
         shallow water of streams and ponds [syn: pickerelweed,
         pickerel weed, wampee, Pontederia cordata]