These very hardy hydrangeas are native to Japan and China but new varieties are coming frm the US and Europe. Blooms are large pyraminds with sterile and fertile florets. Flowers appear in late summer and remain on the plant for months. Most experience dramatic color changes in the fall. Blooms come from new wood and studies show most are hardier than the zone 4 we indicate. Good through zone 8, maybe zone 9 with shade. The paniculata famiy is typically blooming in late summer and continue to bloom well into the fall.