Thanksgiving is a good marker for many garden chores. It is still too early for any pruning, especially for roses, which have not yet gone dormant. You may also want to clean up your perennial beds. I personally like to wait until spring. The stems and dried seed heads can be quite attractive covered in snow. There is a benefit to leaving the stems on as it does protect the root crown. If you feel you must cut them down now, leave at least 6" of stem above the ground.
But here is something to do if you have broadleaf evergreens, such as boxwood, azaleas and rhododendrons. The rain we had last week didn't amount to much at my house and it has been so dry up to this point, it is a good idea to give these plants and your evergreens a long drink of water, especially the azaleas and rhodies, as they are very shallow rooted. Another good practice is to spray them with an anti-transpirant. This is a waxy coating that keeps them from drying out. Wilt-Pruf is one brand, Wilt-Stop from Bonide is another. These pictures from Wilt Pruf show the difference when
one is treated and one is not. The waxy coating prevents the plant from drying out when the ground is frozen and the plant cannot take up water.
Wilt Pruf and Wilt Stop can also be used on holiday greens used in decorating. If you decorate your patio containers for the holidays give them a spray of the Wilt Pruf or Wilt Stop. This will usually keep them looking good through late winter.