They will do fine in containers! Just need to protect from hard frost in a pot. Your house is too warm for overwintering them.--maybe a garage, chilly cellar, the attic... Fact they are so easy in containers adds to he collecting bug. Okay, no more landscaping space so they can always do well in a container and fact that they are deciduous means that don't need light in their winter retreat. Still, I managed to plant 5 more today on a new western exposure fence neighbor recently installed. They transplant well and it is supposed to pour tomorrow. If you do plant again in the ground, make sure you don't make my first mistake with the very first one I got years ago. I bought a big, very robust cultivar and planted too house to the house. They were eventually very big, constantly needed pruning and were removed.

If you can get, and keep, the crepe myrtle to a single trunk, it won't be as wide as a multi-trunked tree. The flowering branches do extend pretty far out, and can hang down/droop gracefully as the blooms open, possibly as wide as tall, but I haven't measured any big ones that were single trunk. That's why I suggested planting further from the sidewalk, so it doesn't block the walk. You could trim any branches that overhung the walkway back to the trunk, although the CM as a whole might look lop-sided. I am not sure you WANT to prune a 20 foot tree to keep it lower, unless you have access to a cherry picker, as it's rather hard to be safe that high up and reaching to prune? (if you are an aerialist, line-man, or professional arborist, then never mind) And CM's don't look good pruned shorter, IMO. Look up "crepe murder" on this forum or Google for it, and find photos of each, and you can see the differences in "murdered" treees and trees left to grow naturally. Trimming for shape is one thing, trimming for height is much harder to do and keep the tree looking natural. Try to find a CM cultivar that won't get taller than you want the ultimate height to be, and be aware that it will take some years for it to grow to that height. While I love lamb's ears, unless you get a non-flowering variety, be aware that it might not be the best for next to a public walkway. The bumble bees LOVE the flowers, and while you do have to work pretty hard to get a bumble bee to sting, it might upset the neighbors and passers-by to hear and see them buzzing happily. Not many people are aware of the differences between bb's and honey bees, and can react badly to any buzzing, bee-like insect.

I realize I am about 9 years too late, and I don't know whether you've already tried growing crape myrtles, but just came across your question. I am a transplant from Texas currently living in the Indy area (zone 6) and missed my crape myrtles more than any other tree/shrub. I doubt you'll ever be able to grow a tree, but I have been successfully growing several varieties in the ground since 2013, even with below zero temps we had this past winter. I did lose a few early on, but once established, they have done very well, even during drought conditions. You MUST have full sun, and southern exposure is best. I wouldn't bother with eastern or northern exposure. I The key to getting them to come back every year is to cut back to about 8-10 inches in fall after blooming then mulch the heck out of them (at least 6 inches) Around mid April, I pull back the mulch and let sun get to the root area. You may not see any sign of growth return until May or June, especially the first few years, but one day you'll check on them and be excited to see leaves sprouting. Once that happens, they grow quickly. Mine start blooming late June to early July. Other than that, they are very low maintenance. The only watering they get is when it rains, and I've never had a problem with insects or diseases. Bees love them. I forget to fertilize, yet they still bloom profusely. Three of the varieties I grow are supposedly miniatures (Mardi Gras, New Orleans, & Cordon Bleu), but they get pretty big by the end of the summer. I also grow a shrub type Purple Velvet which grows to 3-4 feet tall each year. I purchased them at https://www.crapemyrtle.com/store/c2/Miniature_Crape_Myrtles.html They are a little pricey, but worth it, in my opinion. You can call customer service to see what they say about growing in zone 5. If nothing else, you can grow one in a pot and bring it inside, but that's more work than I want to deal with. Follow planting instructions for best success. Hope you find this helpful, and I wish you great success. ️

Crystals..I don't know of anyone who irrigates their crape myrtles beyond the first couple years after planting. And, you may be putting your fertilizer too close to the tree trunks. Here it is 3rd week of Aug and most of the crapes in yards and in pro intallations/street medians are blooming late and fully. We have, in most of Meck. Cty, had more than enough and regular rain. I'd stop babying these decorative small trees and focus on the fall/winter trimming and removal of the drip lines. Move the drip lines at least 6' from the trunk and root ball area or take it away altogether.