Great design is about getting the theme right. What is wrong with this theme?
This modern wall is beach side. It has two types of plants.
Thread Agave, spiky and modern, natural in arid landscapes.
Standard Mexican Orange Blossom, a traditional shape and species from old world Europe. I imagine the owner wanted something to break up the wall? The planting theme is unclear.
By having a firm design boundaries, and one theme, one of the plant types should go. I have removed the standard topiary and added more of the Thread Agave. If the owner still thinks the wall is still too stark, try a darker natural colour on the wall, or encourage leaves from inside the wall like the Puka leaves.