Answer: The most common reasons for lack of bloom are either pruning at the wrong time or the plant is not cold tolerant enough -- meaning it is root hardy but not bud hardy in your area. Your purple flowering hydrange is most likely a big leaf hydrangea and if so, it is probably a winter hardiness issue. Most of these hydrangeas bloom on old wood, meaning branches that grew the year before. Winter damage to the branches or pruning in fall, winter or spring will remove the flowering wood for the coming summer. Spring frosts can also damage the buds for the coming summer. You might try giving it a good wind break, or as extra winter protection you could make a frame around it with burlap and fill that with nonpacking insulating material such as dry oak leaves or straw, and top it with plastic or a tarp to keep it dry. Leave air gaps to avoid condensation and heat building up inside. Put this on in very late fall after the plant is fully dormant and take it off in mid spring. Then be prepared to cover it if spring frosts threaten. Maybe you will see blooms next year. Your oakleaf hydrangeas bloom on new growth so pruning should not be an issue with them but lack of sunlight or overfertilization can keep them from flowering. Make sure your hydrangeas are getting morning sunshine and don't feed them next year. With any luck they will bloom for you. Hope so!
Q&A Library Searching Tips