The Collaborative International Dictionary of English v.0.48:

Leafless \Leaf"less\, a.
   Having no leaves or foliage; bearing no foliage. "Leafless
   groves." --Cowper. -- Leaf"less*ness, n.
   [1913 Webster]

   Leafless plants, plants having no foliage, though leaves
      may be present in the form of scales and bracts. See
      Leaf, n., 1 and 2.
      [1913 Webster]

WordNet (r) 3.0 (2006):

leafless
    adj 1: having no leaves [ant: leafy]