Baileys Nursery in Minnesota revolutionized shade gardening in 2004 with the introduction of Endless Summer™ Hydrangea. It was the first macrophylla hydrangea that could survive a Zone 4 winter, bloom on old or new wood, and consistently produce flowers for an extended time. Before this, you could only get flowers the first year the shrub was planted, and though the roots might survive the cold and push new stems, you would merely have large leaves where you previously had impressive blooms. For this reason be aware when purchasing forced pink or blue potted hydrangeas from the florist at Easter and Mother's Day. These varieties may be more suited to a warmer climate.