, Salem, MA


September 13, 2013

North Shore Gardener: Hydrangea may have been pruned to death

Q: I have a lovely old climbing hydrangea that climbs up and over the porch, but this year the porch has to be painted. I knew this was coming, so last fall I gave the plant a severe haircut. After winter I was anxious to see if it would bloom — but besides not blooming, the rest of the plant looks dead. There are many buds on the branches, some of them green but many of them black or brown. Will my plant survive?

A: I am afraid I have bad news for you: there’s only one chance in a million for survival, and you’re to blame. Climbing hydrangeas should be carefully pruned in late fall after bloom. If ever a major pruning is necessary, do it in stages over a period of years to avoid killing the vine. If a vine is growing in a spot that will need occasional painting and the vine will need occasional pruning, it is quite possible to plant on a trellis that can be carefully pulled away from the structure, then easily reattached when painting is finished — and you’ll never even break a branch.

Q: Do you have any hints on getting my kalanchoe to bloom again? Also, is it lime you use to make your hydrangeas bluer? Would coffee grounds help?

A: Your kalanchoe is a succulent, and like poinsettias and Christmas cacti, it is light-sensitive. The blooming period is late fall to winter. As we all know, those are our low-light short days, but plants are often forced to bloom at other seasons. Try growing them in a totally dark closet or covering them with a large box — take them out every morning just as you would a poinsettia.

Now to the hydrangea: you need to add aluminum sulfate to the soil to turn a hydrangea blue. And they need an acid soil to allow better absorption of aluminum. You are too late for a color change this year, but do use the aluminum this fall and again in the spring. Color change does not happen overnight, but in a season. Use an acid fertilizer as a foliar feed to help keep the soil acid — coffee grounds are OK, but do not have enough acid to change the pH without the aluminum sulfate, too.

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