Crape myrtles flower on new wood, and pruning is an art. If you do it yourself, you risk committing "crape murder," which is unfortunately all too common at shopping centers and street sides here in the South. There's a link to an excellent article from Southern Living below, complete with proper pruning demo pics.

Also, if you've fertilized, there may be a chance you've given the trees too much nitrogen, which is linked to excess foliage and less flowering. Crapes also like at least 6 hours of sun for good flowering.

By the way, "crape" and "crepe" are used interchangeably...both spellings are accepted.

Here is a link that might be useful: Stop Crape Murder

Fertilizer spikes are usually not a good way to fertilize a tree. Other methods and other sources of fertilizer might produce better results IF the trees are in need of fertilizer. Also, ditto what mbuckmaster said about the nitrogen.

The term "crepe myrtle" is a common misspelling of "crape myrtle". Although this mistake is so prevalent that many consider it an alternate, it is actually not the preferred or, according to many experts, the correct spelling.

The 'cutting back' (also called topping) of crapemyrtles often results in excessive succulent growth that is reluctant to form flower buds. Just one more reason not to 'murder' a crapemyrtle. ;-)

Rather than fertilize your trees (and I totally agree that tree spikes are not the way to go), make sure that you have an ample layer of mulch in a large area. Use 2 to 4 inches of chips, bark, or pine straw...but never (ever) pile it up against the trunk like a volcano. Mulching is one of the single most beneficial things you can do for trees.

Thank you all for the advice. From reading your responses, it may be combination of poor pruning, plus not getting the minimum of six hours of sunshine. I'll starting paying better attention to the sun they do get.

Not sure about the mulch, as these trunks are quite large, and thick.

Thanks again.

Mulch is just as good for larger trees as it is for smaller ones. Good mulch is probably the best thing you can do for your trees. It helps retain moisture, it increases soil fertility and improves soil texture when it decomposes, it reduces competition by eliminating or reducing weed growth, it reduces maintenance and helps guard against mower/trimmer damage, and it can improve the look of your landscape.

I agree with Brandon, mulch is good for established trees as well as for newly planted ones. The warning not to pile mulch against the trunks applies - it can cause rot issues further down the road - as well as the depth warning - no more than 4" - and I would mulch as widely as you feel comfortable with - the wider the better.

Mulching is ALL about the soil/root system. If you improve that, then your entire tree responds in a positive manner.