Spring is really the best time. They stress out a bit when transplanted once warm/hot weather sets in. But they're resiliant plants.

I have to admit, though, our summer climate is so mild here in northern Minnesota (I'm very close to Lake Superior) - summer days are rarely hot - so I can get away with transplanting things just about any time during the season. Others will have different experiences.

i would do it when leafless ... for easiest transplant ...

second choice .... i would do it after flowering ...

they are near impossible to kill outright with basic aftercare [PROPER watering, ask if you dont know what that means] .. and i dont know why you cant wait until leaf fall ... and just move it then ... fall or winter ...

and i would butcher it for ease of moving.. even if it meant i lost next years flowering ...

you dont really mention how big it is.. so its hard to be more precise ...

ken

Your suggestion to transplant in the fall is very good and we'll do just that. Thank you