The Collaborative International Dictionary of English v.0.48:

Yaupon \Yau"pon\, n. (Bot.)
   A shrub (Ilex Cassine) of the Holly family, native from
   Virginia to Florida. The smooth elliptical leaves are used as
   a substitute for tea, and were formerly used in preparing the
   black drink of the Indians of North Carolina. Called also
   South-Sea tea. [Written also yapon, youpon, and
   yupon.]
   [1913 Webster]