The Collaborative International Dictionary of English v.0.48:

Unfruitful \Un*fruit"ful\, a.
   Not producing fruit or offspring; unproductive; infertile;
   barren; sterile; as, an unfruitful tree or animal; unfruitful
   soil; an unfruitful life or effort. -- Un*fruit"ful*ly,
   adv. -- Un*fruit"ful*ness, n.
   [1913 Webster]