Purchased my house in Sugar Land (zone 9) October 2015 and I am working on my shady back yard this year. Had the oaks and Chinese Tallows thinned and pruned to allow more light for the grass. Every bed is lined with these rocks; must be hundreds of them. The ground covers are coming back after the freeze (Arrowhead and Dotted Bridal Veil) and I am working on a bed close to the house where a giant Sago Palm was removed. But this gap along the back fence is bothering me!

A small flowering tree might work; it is relatively clear above and should get enough sun. I don't want anything that has to be pruned. Suggestions? or should I just try to thin/transplant the ones along the fence to fill in? And what are they called anyways?

I am on a curved street so this is roughly looking Northeast.