Thursday, December 20, 2007
The bigleaf hydrangea has dropped its leaves to reveal a twiggy mess. But put away those pruners.
The impulse to cut it back, as though it were a perennial, will result in lost flowers next June. The bigleaf hydrangea produces its distinctive mophead or lacecap blooms on wood formed the previous year, so a haircut now will destroy the lateral buds that otherwise will swell and grow in the spring.
Even left unpruned, next year's buds are still vulnerable to winter dieback in a prolonged freeze, so think about covering the plant with a light blanket during periods of deep freezes this winter.
The new growth, when it breaks in April, is also at risk from late frosts, so make a point of covering the plant in early spring if the buds have broken growth and a frost is forecast.
If you have an established hydrangea that has become too congested, you should remove up to a quarter of the oldest canes to open up the bush and promote larger blooms. Do that, however, in May, after the danger of frost has passed.
Two new varieties of bigleaf hydrangea, Endless Summer and Blushing Bride, uncharacteristically produce flowers on new wood, so they are not prone to winter damage. However, for maximum show next year, leave them alone now.
For advice on pruning the related oakleaf hydrangea, see the Digging In column on Page 6. Annabelle and other popular varieties of the smooth hydrangea bloom on new wood, so you may hack away now to your heart's content.