Hi, I'm looking for recommendations for low evergreens that can grow in the shade under larger pines, oak, birch stands. These trees would serve two purposes: 1. Screening under and adjacent to larger trees up to ~6' height where branches are 6'+ from the ground. 2. Create greater shade to prevent growth of Buckthorn. These evergreens must be relatively low maintenance (no covering in winter) and suited to MN climate. Any suggestions are welcome. Thank, Mark