Question
I have a red rocket crepemyrtle about 1 foot high. What fertilzer to add for more blooms on my crepe. zone 8b.

Answer
Red Rocket, a deciduous scarlet-flowered 7-year-old Crepe Myrtle hybrid ('Lagerstoemia indica' to botanists), begins blooming in July in the north.  Its cone-shaped clusters can get huge, provided you don't prune this plant wrong.  Never prune a Crepe Myrtle after growth starts in the spring; you'll clip the blooming growth off and delay flowers a full year.

Besides a ton of sun, these trees need close attention to watering, especially in the South where they are prone to dry out, and especially when they are small and root systems are still developing.  The pH must be on the acid side.

Although they need Phosphorous to bloom, young Crepes really need the rich soil even more for blooms to reach their potential.  Homeowners who use high-Nitrogen tree fertilizer spikes to feed this plant will find foliage without flowers.

Instead, top-dress your Crepe Myrtle with Bone Meal, which is high in natural Phosphorous, and Mushroom Compost.  They won't burn the plant and they'll conditino the soil it is growing in.  Phosphorous also builds strong, healthy roots.

When you do get blooms, be sure to cut them off once they fade.  This is a good practice with any flowering plant or shrub, but one people pay less attention to with outdoor plantings.  It keeps the plant from pouring energy into seed production.  Any saved energy will be used for the next flush of flowers.

Your Crepe is small.  This is the time to train it for future shaping.  Do you want it to develop into a curbside or yard tree eventually?  Remove suckers from the base and train to a single trunk.  On a more shrubby plant, keep the interior thinned to encourage air circulation.

These are hardy all the way up here to Zone 6.  We don't have enough of them.

Thanks for writing.  Any more questions, I'm here.