|We own a garden center in Iowa. Zones 4-5. We have had a few customers asking about a new|
|I am inclined to be as disbelieving as you are. I suspect your customers may have seen ads such as the following at|
or discussions such as this one
and assumed this meant winter hardy when grown outdoors in the ground. Careful reading qualifies it to being in containers brought into a sheltered place for the winter.
As far as I know, the hardiest are still those developed at the US National Arboretum. Most nurseries list the hardiest as being reliable to zone 6, a few will stretch it to zone 5 for selected among these varieties. And, this may be root hardy rather than completely stem hardy. (The Monrovia listing shows zone 6 at the coldest for selected crepe myrtles.)
Although we would all probably like to see some hardier crepe myrtles, I hope this helps.