I am in a watching mode over here. Same thing happened to my new one planted last year. The wood underneath is still green so I am hopeful but the next month should tell me more. Maybe someone has a better answer for you then mine since it's a wait and see. Cher

Natches Crepe myrtles usually grow fast when they are young and are one of the potentially tallest growing cultivars of CMs. Yours likely get the right amount of water they like during their spring growth flush, and the nitrogen issue will definately compound that fast growth issue. The tree that is not blooming could be getting less direct sun rays. Is there a tall tree or some other structure that is out of the shot, but which is tall enough to cast signifcant hours of shade on that CM. If so that could be another reason you CM is not blooming yet, even though the Natches on the other end of the house has begun to bloom. Personally if I wanted a corner accent CMs I would not have chosen the Natches cultivar. Especially considering that those multi trunks have the potential to get overly thick and the canopy they each produce can end up being more massive than one would think they might want spreading so close to the corner of house. Guess to avoid such issues, either late winter or very early next spring, you could do corrective pruning that transforms your Cms to single trunk trees. but whether or not you choose to do that you will find the you also will need to yearly raise each tree's canopy, until the yearly pruning time arrives when your trees are tall enough that their canopies are higher than your roof line and are no longer close enough to hang down on and brush against your house shingles.

I had two HUGE crepe myrtles in the yard of my last house (rented)...they were the biggest c.m.'s I've ever seen, even compared to south LA or Natchez, MS. They had to be 100 years old. But they didn't bloom much. They did need a good pruning, and I never supplemented their water. Here in my current home (mine, not rented, woo hoo!) there are some that were already planted. I don't know how old they are, but not young. I would estimate anywhere from 20-40, maybe more. The people who owned this house before me lived here for 50 years and probably planted them soon after moving here. The ones that are in the open bloom the most. The ones that are next to a fence between here and the neighbor's yard have several trees encroaching upon them and can't grow like they should. Just wait till I get my hands on a chain saw...those trees along the fence line are TOAST! lol (The neighbor won't mind, we've discussed it, they are volunteer trash trees.) But they DO get more water because I have made a shrub/perennial border all around them, and their blooms are larger than the others, thought fewer because of limited sunlight. I believe crepe myrtles are long-lived and that is not the problem. I would check sun, pruning, or water. Do a search on pruning crepe myrtles on this forum to avoid being advised to "crepe murder" them!

The plant needs more phosphorous. What do you fertilize it with? If you want more blooms than growth, you need a fertilizer with a larger middle number. Also, a crape myrtle that is planted in a heavily fertilized lawn will often do this, because it is getting too much nitrogen. Look at those planted along roadways. They are never fertilized and they bloom like crazy. Crape myrtles really do thrive on neglect. Also, they like to be dry, so if a sprinkler is hitting them all the time, they sometimes will put out vegetative growth and not bloom well.