Answer: One of the most commonly used evergreens for tall, narrow spaces is Thuja (also called arborvitae). Consider Thuja occidentalis 'Emerald' which grows 10 to 15 feet tall and 3 to 4 feet wide, or 'Pyramidalis' which grows 25 feet tall and about 5 feet wide. Either can be planted 4' apart and allowed to fill in the bare space you describe. Good luck with your landscape.
Q&A Library Searching Tips