From the ArcaMax Publishing, Trivia Newsletter:
http://www.arcamax.com/news/trivia/s-274389-910098
Cultured Christmas trees must be shaped as they grow to produce fuller foliage. To slow the upward growth and to encourage branching, they are hand-clipped in each spring. Trees grown in the wild have sparser branches, and are known in the industry as "Charlie Brown" trees.
This news arrived on: 12/16/2007