Welcome Tom, Congratulations on growing some tropicals in Brooklyn. Wow, global warming is causing at least one positive!
I can't help you with specific varieties for your locale but can tell you I have seen many CM's on the Jersey Shore and you are not that much further north. I gave several unknown varieties to my late in-laws up there and they did very well.
One thing you have to remember is that they leaf out very late, causing you to think they might not have made it. Usually around June you would start to see a few little leaves. Good luck.

I will buy a couple and plant them early next fall so as to let them root thmeselves firmly. Should I immediately put a mulch or sod around them after planting???

Will this help stop suckering and other undergrowth?

Tom - The only way to prevent suckering with a crape myrtle is cement, and even then they will find a way to send up new volunteers. But that is not a bad thing - I have potted up several volunteers from my huge, gorgeous crape myrtle (put in by the builder, so I don't know what it is) and already some of my neighbors and friends have put in claims for them. If you do any gardening under the crape myrtle (I plant herbs under mine), where you disturb the roots new plants will come up. They are easy to weed out when small if you don't want them.

Another feature - if your summers are long enough. I tried this for the first time this year. Cut off the newly forming seed pods as the flowers fade and they will bloom again. My second bloom was more spectacular than the first, so I am trying for a third. It takes a few weeks for the next set of flower buds to appear.

I hope you find a crape myrtle that works in your yard because they are wonderful plants. Good luck.

Tom, On another forum (Southern Gardening or Carolina Gardening perhaps) a woman from Pennsylvania mentions she has had good luck with the 'Hopi' crepe Myrtle. You might want to search and see what she says about it.

Tom:
I'm a big fan of Fairweather Gardens in NJ (I think I must have touted them on every crape myrtle post so far, as I'm buying one this year too.)

They charge $4 for a catalog, but it's worth it. Incredible variety, large plants. Best of all would be to go to one of their open houses. I plan to this Spring too.

(856) 451-6261

I suggest that you determine the space that you have for future growth before you select your crApe myrtle cultivar. You don't want to be hacking them down to nubs every year to keep them within bounds. If you give me a mature size limit, I will help match you with an appropriate crape myrtle variety! How's that for a deal?

Email directly, as I do not check this forum regularly.

If you've had luck with tropical plants its just Purly Luck! Remember the next shot of cold weather or big snowstorm which is probally common north of Virginia could do significant damage to your plants. Oh yea According to the USDA Brooklyn is a growing zone of 6A.

Zones are misleading. Remember that the USDA temperature zone is an indication of the 'average lowest temperature' in an area. Brooklyn, like most coastal areas, benefits from the buffering effects of a large body of water. It does not receive the extreme cold or the extreme heat of more centrally located 6a areas.

I am always quite surprised when I visit relatives along the coast of NY. It is quite temperate.

The NYC area recieves more snow and has alot more occurences of freezing nights than we do here in the south, making it difficult for trees to recover from a low reading even in the city.