You can trim a tree in USDA Plant Hardiness Zone 5 during January as long as you wait until the coldest part of the winter season has passed. The cuts to the tree branches heal faster during warmer winter days. It is a good idea to consult a local nursery or botanic gardens for the best pruning days in your area.
About this Author
Bobbie Brewer has been writing since 1990. Her work has appeared in publications and on Web sites including Garden Guides and Trails. Brewer is an international traveler, outdoors enthusiast and has been gardening since 1991. She has a Bachelor of Arts in English from California State University, Sacramento.