To Tree or Not to Tree, That Is the Question

My husband and I are trying to determine if we are going to put up our Christmas tree this year.  Our son is 20 months old and gets into everything.  He is also testing his boundaries more than ever.  He has this mischievous smile when he knows he is getting into something that he shouldn't be.

If you put up a tree with your little one, how did you keep him/her away from it or child-proof it?