emerald arborvitae - A good plant for a wall of green with minimal maintenence is Emerald Green arborvitae. Just needs a trimming once a year to keep it at the height you want, and in the spring, just tye up and branches that the snow bent.
Windbreak tree: Green Giant Arborvitae (Thuja standishii x plicata 'Green Giant') Fast Growing Evergreen Tree, up to per year. Great Screen, Hedge, or Windbreak. Plant to apart. Grows to high with to spread. Zones 5 to