Source : Webster's Revised Unabridged Dictionary (1913)

Leaf \Leaf\, v. i. [imp. & p. p. {Leafed}; p. pr. & vb. n.
   {Leafing}.]
   To shoot out leaves; to produce leaves; to leave; as, the
   trees leaf in May.

Source : WordNet®

leafing
     n : (botany) the process of forming leaves [syn: {foliation}]