Brief question about crape myrtle and hardiness zones? (landscape, growing, 2015)

[Isleofpalms85]

I have read some conflicting information as to the hardiness zones of crape myrtle and what zone the hardiest varieties can grow. Most online sources claim they are only hardy to USDA hardiness zones 7 or warmer, yet I have read other sources that claim people have had success growing them in zones colder than zone 7. When I lived in central Indiana(Indianapolis area), I saw a number of people growing crape myrtles as a “Dieback to the soil” perennial woody sub-shrub that as I alluded to would die back to the soil line but would sprout up around the end of April and would then bloom late July or early August for a late season flush of color when much of the surrounding landscape was tired and dry looking.

I would like to verify as the locals who grew crape myrtles in Indianapolis area claimed that the particular cultivar they had was “Root-Hardy”, whatever that’s supposed mean. Indianapolis had been considered strictly a zone 5, until the update in 2012 bumped the Indianapolis area up from a 5a/5b in 1990 to a zone 5b/6a in 2012. I even remember seeing a lone specimen of crape myrtle on the far northern suburbs of Indianapolis(Noblesville), and this shrub had survived the winters(even if only as a “Die-back woody perennial shrub-let”) since late 2014 or early 2015, I suspect the thing had first been planted the spring of 2014.
So I would like to know from anyone else who “Experiments” with trees or shrubs not normally associated with the hardiness zones that you live in. So, my questions are the following

Does/Has anyone on the C-D garden forum know how “ Hardy” the hardiest crape myrtle cultivars are, I.e. is the hardiness zone limit of successful cultivation a zone 7a, possibly a zone 6 or possibly even the warmer half of zone 5, please please help me because I have always wondered about this ever since I ever saw crape myrtles of any kind being grown in the Indianapolis area.

So please someone if you know or have an idea please answer this thread, thank you and sorry for such a long drawn out post

[gentlearts]

I googled hardy crape myrtle and zone 5 seems to be the coldest zone for them.

https://www.crapemyrtle.com/store/c1...e_Myrtles.html

[BobHoward]

I consider Michael Dirr to be the best reference for woody trees and shrubs that grow in temperate climates. Mr. Dirr puts crape myrtles in zone 7 (0 degrees F), with zone 6 (-10) at best. Not quite as hardy, but otherwise that hardiness pattern applies to southern magnolias as well. I've seen lage trees in Washington DC (on the White House grounds - in zone 7). In borderline places like Louisville, KY, I saw southern magnolias as mid-size, many-stemmed trees, which implies that at some point, they died back, but the roots survived. I think duration of cold may be more of a factor than lowest temperature.

[lammius]

I have a Cherry Dazzle crape in a small raised bed. The plant was noted by the seller to be hardy to Zone 6. That's the coldest zone I've seen a crape categorized. Most seem to be labeled Zone 7-10.

I'm in 7B, and the Cherry Dazzle does very well here. Mine starts blooming much later than most other crapes in the area, but I think that's because I have it in a spot with part shade.

[Isleofpalms85]

The small shrub crape myrtle in noblesville Indiana(North suburban area of Indy) apparently survived as a shrub with very little or no dieback the winter of 2018-2019, when there was a night that got down to around -10 F/ -23 C for a couple of hours. The winter of 2017-2018 that same shrub was killed to the ground but the roots apparently survived the arctic blast that winter and it sprouted from the roots up. I don’t know if the severity of the cold temperatures or the duration of the cold has more of an impact on whether certain trees and shrubs including crape myrtles survive the winter cold or not. So I’m presuming that particular crape myrtle is rated as solidly hardy through zone 6.

[Isleofpalms85]

Originally Posted by BobHoward

I consider Michael Dirr to be the best reference for woody trees and shrubs that grow in temperate climates. Mr. Dirr puts crape myrtles in zone 7 (0 degrees F), with zone 6 (-10) at best. Not quite as hardy, but otherwise that hardiness pattern applies to southern magnolias as well. I've seen lage trees in Washington DC (on the White House grounds - in zone 7). In borderline places like Louisville, KY, I saw southern magnolias as mid-size, many-stemmed trees, which implies that at some point, they died back, but the roots survived. I think duration of cold may be more of a factor than lowest temperature.

I have seen an increasing number of southern magnolias in the Indianapolis area(presumably the cold hardy varieties like bracken’s brown beauty or Edith bouge) being planted in the last at least 15 years or so. I’d imagine the hardiest southern magnolias would be hardy through zone 6a( -5 F to -10 F). The winter of 2013/2014 completely defoliated some hardy cultivars of southern magnolias when the temperatures got down to -10 F to -15 F for two consecutive nights but apparently many of those trees apparently survived and recovered from that cold blast IIRC.

[NorthofHere]

I have seem them in Massachusetts on the Cape but you probably want to buy them from a nursery in your area because they will most likely have a variety that survives. Just please, don't crepe murder (look it up). We had crepe myrtles in upstate South Carolina (zone 7) where we had a few winters that had snow and colder weather than normal and all my crepe myrtles survived.