Q.red tip photinia pruning
I purchased 9 red tip photinias with multiple branches from the base. How do I prune into one trunk to look like a tree? Do I prune just after last frost? I live in north Texas and will be planting them this week.

Certified GKH Gardening Expert
I would wait till after last frost to prune.
To train the plants into a tree shape, choose a few string leader stems and remove all of the weaker and smaller stems from both the base and the small lateral branches from the sides of the leader branches up to where you want the canopy to start. This article will also outline how to do this in the "Shaping Tree-Form Shrubs" section:
http://www.clemson.edu/extension/hgic/plants/landscape/shrubs/hgic1053.html