The Collaborative International Dictionary of English v.0.48:

Wych-elm \Wych"-elm`\, n. [OE. wiche a kind of elm, AS. wice a
   kind of tree. Cf. Wicker.] (Bot.)
   A species of elm (Ulmus montana) found in Northern and
   Western Europe; Scotch elm.
   [1913 Webster]

   Note: By confusion this word is often written witch-elm.
         [1913 Webster]