Grows well here, but this year, along with many others, did not do much. Multiplies well. Reblooms many years. Performance has been uneven the last few years--not surprising given the weather vagaries. I would say that it may not do well in zones above here (6a), but there are so many factors other than zone temperatures. A few years ago we had a very cold winter with hardly any snow cover, and gardeners far north of here had fewer adverse winter impacts than we did.
Six inches seems a bit bigger than the blooms here.
