Young plants need to use their energy putting down good roots & establishing themselves as healthy organisms before they begin to flower.
I wouldn't stress them out by any pruning right now.

Crepe myrtles are long-lived ornamental trees (or shrubs, depending on the cultivar), & they need time to grow into their mature size & shape to best grace your landscape or garden.

I occasionally see where someone has hacked the ends off the limbs of crepes, which increases the flowering tips but butchers the beauty & grace of the tree:

The effect makes me think of fingers growing from someone's wrists. Someone on another forum said it reminded him/her of a Dr Seuss effect.

When I first planted my crepes, I didn't know a thing:
nuthin' about gardening, nuthin' about crepe myrtles, nuthin' about planning, nuthin'.
I was lucky: I didn't have any shade, so they're all planted in sun, as they should be, North Central Texas is an ideal place for crepes, & my neighbor has been very nice about the 2 I planted *right on* the property line, & which now shade part of his lot & drop their crepe-papery petals on his pick-up truck!

I didn't touch the crepes, as far as pruning, for a number of years, & they're now huge, gorgeous trees, easily the most beautiful things in my landscape.

I'd say be nice to them, & plant some hot-weather annuals like zinnias for immediate "bang for the buck".

Good luck & have fun!

sylvia

ps: You chose well. I think crepe myrtles are easily the most beautiful trees we have in the south.

Selective pruning in late winter/early spring can get them to branch out fuller. If you want them like shrubs you could have planted the dwarf variety.

The most beneficial thing you can do is to add a substantial layer of good organic mulch around the tree's root zone. Few people appreciate the importance of this simple task. The mulch should be applied all around the trunk though should not be piled up on the trunk itself. You don't want to achieve that 'volcano' appearance so beloved by ignorant landscapers!!! The use of 2 to 4 inches of mulch is enough to benefit the soil/root system of your crApe myrtle. Avoid the use of fertilizers, too, as this tend to create lanky, leggy growth in crape myrtles.

Thank you so much, everyone:) I am very excited to learn there are shrub variety:):):) I was driving through a particular area of Little Rock and there were these short, fat, beautifully bloomed crepe myrtles everywhere. It was stunning, to say the least. I am going to buy a ton of them, as soon as I can find some!
Thanks again,
Jen

Just a quick add-on to this crepe myrtle thread...I read some very lengthy articles and did a great deal of research on crepe myrtles while I was waiting to trade for one...any color, it didn't matter to me since I think they are all beautiful, tho the fuschia-colored ones seem to have fuller blossoming power. All the articles I read said not to buy bare root crepe myrtles, that they do not handle that well. Always purchase with the original burlap root bundle. Long story short, I was walking next to an old, overgrown field where this lonely, absolutely beautiful crepe myrtle has been growing for years, and there was a perfect sized baby under it. Well, I dug and I dug and fussed and fussed under the hot Louisiana sun, and finally I got that roughly 1.5' baby, completely bare rooted, and just stuck it in the ground with a little peat in the hole in the full sun. It has fared very, very well. Tons of new growth all over it and I have done very little to it, except water it religiously for the first week or so and watered a couple times with water from my fish pond. The other baby left under the mother tree was a little taller, perhaps 3' tall, and was full of blooms. I must have a hardy variety, because all summer, it has taken so very little attention.