I planted a hydrangea 3 years ago. The last 2 springs resulted in existing branches not leafing out. Leafing does however initiate at the base of the plant. Is this common to some hydrangea plants? I have a different type of hydrangea plant which does not exhibit this condition. Could you please give me some insight to this plant condition--is it normal or is there something I can do to prevent this from happening in the future ?