Tall bush/tree for narrow foundation bed
I'm looking for plant ideas to fill in a narrow space on the side of my front porch foundation. Ideally, I need 2 plants, each of which will be 10 feet tall, 3-4 feet wide as mature size. I'll post 2 design photos here.
Photo #1 shows the bed which is on the left side of the front porch.
Photo #2 demonstrates the idea by putting two 10-feet Thuja occidentalis 'Smaragd' there.
But I'm hesitate to use Smaragd due to:
1) My research draws a conclusion that they won't stop at 10 feet, instead they will gorw up to 15-18 feet high which is obvious too high for me
2) I'm a bit concerned of putting such a large tree right beside the foundation.
Since I live in southern Ontario Canada (Zone 4), my selection is limited. I'm having a hard time to find anything that fits my need. Anybody here has idea/thought?