A nasty frost in April turned the buds black on my Hydrangea macrophylla. There was a lot of new growth in spring, but not one flower this summer. What can I do to ensure spectacular blooms for next summer?
Mary Bentz, Bethesda, MD
A burlap shelter will protect hydrangea buds from frost.
Photo/Illustration: Christine Erikson
Keith Davitt, horticulturist and author in Brooklyn, New York, replies: Although there is said to be a cultivar— ‘All Summer Beauty’—that blooms on new wood, nearly all H. macrophylla varieties bloom on last year’s wood. If the nascent flower buds were damaged in the spring by frost, that is likely the cause of their failure to bloom. However, with proper care this season, next year’s blooms should be spectacular.
Occasional applications of compost forked into the soil will give your hydrangeas an excellent environment for root development. A year-round mulch will also help maintain moisture and evenness of ground temperature. Cut out old wood at the base and any weak or spindly branches at their point of origin. Use a balanced fertilizer high in nitrogen during the active growing season, then taper off the nitrogen and provide only phosphorus and potassium toward bloom time.
As winter approaches, mound up fir branches, straw, or whatever you can find, or build a cylindrical shelter from stakes and burlap to keep in place until all danger of frost has past. This extra protection will prevent or diminish winterkill and assure you of beautiful blossoms next summer.