The Collaborative International Dictionary of English v.0.48:
Birken \Birk"en\, v. t. [From 1st Birk.] To whip with a birch or rod. [Obs.] [1913 Webster]The Collaborative International Dictionary of English v.0.48:
Birken \Birk"en\, a. Birchen; as, birken groves. --Burns. [1913 Webster]WordNet (r) 3.0 (2006):
birken adj 1: consisting of or made of wood of the birch tree [syn: birch, birchen, birken]