If I cut the trees down three months before the season, will it effect the deer? Should I clear out the ferns, or do they eat them?
Yes, I would say that it probably would especially if you are talking about a substantial amount. As mentioned above I would do a minimal amount of "trimming" for shooting lanes and nothing more. The more you cut the greater the potential for the deer to take notice and change their patterns.
As for the ferns...I don't recall ever seeing or hearing about a deer eating them.