Summer and intense heat in northern regions is different from summer and intense heat in Midwest and southern regions. Plus, plants in hotter areas in the garden can usually take it if there is extra water. Plus, look at planting in the spring or fall rather than summer. With summertime planting, shrubs are so worked up over dealing with shock of being moved and heat, that they are fussing with that rather than growing roots and getting established. With all that in mind, Diamond Rouge is a paniculata hydrangea. And, paniculatas like sunny spots. Follow our planting and care guide, and it should get off to a good start. With your zone 3 garden, it will be important to prepare your hydrangea for winter. Take a look at my video for winter preparation tips.
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