The Collaborative International Dictionary of English v.0.48:

Bourgeon \Bour"geon\, v. i. [OE. burjoun a bud, burjounen to
   bud, F. bourgeon a bud, bourgeonner to bud; cf. OHG. burjan
   to raise.]
   To sprout; to put forth buds; to shoot forth, as a branch.
   [1913 Webster]

         Gayly to bourgeon and broadly to grow.   --Sir W.
                                                  Scott.
   [1913 Webster]

WordNet (r) 3.0 (2006):

bourgeon
    v 1: produce buds, branches, or germinate; "the potatoes
         sprouted" [syn: shoot, spud, germinate, pullulate,
         bourgeon, burgeon forth, sprout]