It might be helpful if you could find a pic of what you dream yours look like in a few yrs, and ask for advice for working toward that goal. When I first read your post, I got the impression you wanted them to look like trees, but with the way those start branching so heavily, so close to the ground, I'm not sure I'm clear yet about what your goal is for these plants.
There are a ton of pics in the various entries for various Lagerstroemias in the plant database on this site.
http://garden.org/plants/searc...
If you're unsure which yours are, the general entry also has many pics, though most are closer macros of blooms:
Crepe Myrtles (Lagerstroemia)
If you see a pic in the plant database on this site that demonstrates what you envision your plants looking like in the future, click on it and it will enlarge. Then you can show it in a post in this discussion by pasting this string right above the pic:
[ db_photo]124808[/db_photo ] (without the spaces I added.)
