"Why doesn't my hydrangea bloom?" It's the most asked question on my Sunday morning radio show. One of the most popular types of hydrangea is Hydrangea macrophylla, it's the lacecap or mophead variety and most put their buds on during the summer right after blooming.
If for some reason those buds are removed either in the early spring before bloom or later, then the plant won't have flowers. Another thing that can happen, is that the buds can freeze out in the winter. Surrounding a plant with burlap and making sure it gets plenty of water before the ground freezes can help keep the buds viable. Here's a place to learn more about hydrangeas.
There are macrophyllas that will bloom on old AND new wood, one example would be Endless Summer, it's popular and a more reliable bloomer in zone 5-6 which is the climate around Pittsburgh and the surrounding area.
Hydrangea arborescens is the family that inlcudes 'Annabelle,' a beautiful and reliable bloomer, They always bloom on new growth, so this variety can be cut to the ground at the end of the season. There's a cool pink variety that will be available in the spring too.
But my favorite variety might be Hydrangea quercifolia or 'Oak Leaf' hydrangea. The leaves are big and shaped like oak leaves, the plant puts on large conical white blooms and has a wonderful burnt orange bark for winter interest. It blooms very well in our climate.
If you're having trouble getting your macrophyllas to bloom try a different type or the burlap technique. You'll be happy you did when they start blooming in early summer.