It helps to know your zone, but without knowing your state these trees might not be available in your area.* I might recommend different trees and/or shrubs if you are in zone 8 in Georgia then if you are in zone 8 in Arizona.* What state are you in?* Since you mention a Texas red oak, are you in Texas?
I'm also a bit confused because you say the north side has the tree but you need a tree/shrub for the west side.* Maybe the tree is on the nw corner and it shades the west side?* Just how much sun, if any, does the area get?
Is this the same request as here?
When weeding, the best way to make sure you are removing a weed and not a valuable plant is to pull on it. If it comes out of the ground easily, it is a valuable plant.