What you described about the multiple branches radiating around the trunk, just below where the trunk has been top cut, is a typical growth pattern for such drastic top pruning. All too often growers have already done such pruning to larger crape myrtles when they are shipped to the retail nurseries. Did your area get the recent days' hard freeze around the Easter holiday? If so the CM in question might have a lot of dead wood which needs to be pruned out. If such a freeze happened, watch the tree as its remaining buds leaf out again. Once the tree appears to be fully leafing out enough to look recovered from any winter or freeze damage; totally remove any trunks or branches which fail to releaf. Also from the trunks nearest your house, completely remove all the way to the trunk any branches in the canopy which you can clearly tell will grow to infringe on your roof. Throughout the following growing seasons feed the tree with slow release quality food, and after every week which fails to provide an inch of rain for the shrub, suppliment the tree with that much water. Over the summer let the tree bloom naturally, and do not prune off the resulting seeds in an effort to extend your bloom season to the first freeze of late fall or early winter. By letting the tree bloom by itself and by being patient if it seems to slow down in bloom presentation after the first bloom flush; the tree will be enabled to put forth effort into thickening its branches and developing its proper rooting perportions. After the tree goes dormant, depending on when temps drop low enough for that, consider the space which any branching from the trunks still invade your roof line. cut, at that time, each trunk, all the way down to the root ball, whose canopy clearly will grow to infringe on your roof line. Hopefully when you have accomplished all the above pruning you will end up with the best of either a one or three main leader trunks. Then, in early march of the next year, prune out again all brittle dead wood, brake off the remaining seed pods and their twigs. Then turn your focus onto any remaining radiating branches which are growing just beneath the previously described, chopped off trunks. Preserve only a flexible and clearly healthy branch which grows the most directly upward and toward the direction where you want the trunk to continue growing. Prune away any other branches which are growing around the trunk near the same level of the healthy upward growing branch you selected to retain. To repeat: the one branch you choose to keep growing off the end of such chopped off trunks should be the one out of the ratiating bunches which appeares to be growing most upright, and growing in the right direction for the retained branch to assume the role of developing into a continuation of the trunk. Hopefully each single branch you select to continue the remaining trunks are thick enough to survive the following winter freezes. If not you will need to wrap each and their tunks with cotton insulator wrap prior to each freeze. If the temps are forecast to drop down to a hard freeze than add bubble wrap around the cotton wrap. Just be sure to remove the plastic bubble wrap any time the temps rise back up above 33 F. degrees. The above advised action takes a lot of dilligent effort, so if you do not think the tree is worth the trouble, simply remove it, grind the stump and main roots and purchase a 10 to 15 gallon sized, 25 to 30 feet potential height grower Crape Myrtle which has not also already been such drastically top pruned-down by the grower. With any such new CM tree you plant in the area, make certain to plant it far enough from the house to prevent roof damage, and to also prune train it properly each year just as you first described above.

Usually it is best to wait until fall to cut them back. I would also try to find out why the other two trunks died out. Give it a little plant food while you're investigating to help it out. You also might want to mulch around it if you haven't already, (but always pull the mulch a few inches away from the trunk.) These are hardy trees, they come in all sorts of colors and sizes, and most grow very fast. Some people cut them to within a foot of the ground like a bush and others let them grow into a tree, (as you are doing.) I always cut mine back in the fall, and it always comes back; bigger and better! I've also found that some trees start putting out lots of shoots near the base because they have been injured in some way. Its like a trees last-ditch effort at survival. There is a reason those two trunks died; try to find out why, and I would leave those other shoots alone until I knew for sure that the tree wasn't being threatened in some way that might kill the other, healthy, shoots. The first thing I do in a situation like this is take a very good look at the plant, its leaves, and surroundings. Are the leaves injured or discolored? Do they have spots, etc.? Do they fall off easily? Are there carpenter ants in the tree or an ant bed nearby? Is grass at the base or is a large tree nearby, (competing for water/nutrients.) If nothing is visible, then start thinking about the soil. Is it full of rocks/clay? Is it moist all the time? Dry and cracked? Very compacted, (hard?) Sometimes certain plants cannot grow along side one another as well and there is always the possibility that your soil needs to be amended. I hope this helps. It's where I would start. Good luck!

I very much like that tall one! I cut off a couple of suckers the other day, I don't want it to be super crazy with lots of trunks, but I want to be able to shape it how I want as it grows so if I only kept the main I would have been limited. I am not surewhatt variety I have, it came from arbor day society a couple of yrs ago and was in a not good spot so growth was slow, but their site might name the variety, I'll have to search. I would love it to be small to medium tree, but I'll take what I can get!

No one can say as we have NO IDEA where on earth you are located. Location matters, especially when considering growing in a container year-round.