I believe Zones 4-8 but you'd have to check the specific cultivar. I was trying to add to the database on that info and found one website said 5-8, another said 4-7. I'm in 8b and both cultivars I have are thriving, so I can say for certain 8 is good. I watered them in well the first couple years but have done very little since then. One is on a hillside out of range of a hose, the other is in the yard and does get sporadic watering in late summer. I have not fertilized either one.
