Hydrangea Hints

Cape Cod's favorite shrub has been in glorious bloom this year because the winter temperatures last season didn't go below 12 degrees. Because of the relatively mild winter, most of the buds made it through the cold and went on to bloom this summer. Lucky us!

This is a photo of a Nikko Blue that has been cut back in the fall or spring, probably to "neaten things up." Notice that it has grown just as tall as it was last year, and that it doesn't have many flowers. If you want your Nikko Blue hydrangeas to be flower-filled, don't cut them back. Remember that even if you prune them, they'll replace their growth in just one year. There is no making a Nikko Blue shorter.

Here are some suggestions for success with Hydrangeas:

Blooming & Not Blooming

Hydrangeas may not bloom for the following reasons:

1. Too much shade: plant them where they get at least 3 hours of direct sun for the best flowering.

2. Pruning: If you cut down the canes of most mopheads and lacecaps (H. macrophylla & H. serrata) you’ll have fewer or no flowers the following summer no matter when you do it. See pruning below.

3. Winter temperatures that go down to zero or below: this zaps the buds, killing the flowers for the next summer.

4. Warm March temps followed by a cold April: If the buds begin to swell early in the spring, and then get hit by cold, April off-ocean winds, that can be cold enough to kill the germ of the flower.

5. Too much nitrogen: Since nitrogen encourages leaf growth, too much can cause the plants to just make foliage. The most common source of too much nitrogen is lawn fertilizer.

Pruning

Prune pink and blue types in early May by removing deadwood only. Since hydrangeas will replace their growth in one summer, give up on keeping them short. Prune H. aborescens and H. paniculata (usually white) in the spring by first removing deadwood, then shaping as desired. Prune climbing hydrangeas right after flowering. Click here to read and download a pdf of C.L. Fornari's How To Prune Hydrangea Handout.

Using Hydrangeas in Your Landscape ~ Some tips for success:

1. Group hydrangeas together, or with other plants that appreciate more water. Don’t place hydrangeas next to plants that like it dry, such as sedum or junipers.

2. There are many shorter growing varieties for foundation plantings that won’t grow above the windows. Look for Endless Summer, Penny Mac, and plants in the Forever & Ever and CityLine series.  

3. Nikko Blue, the Cape’s favorite blue hydrangea, grows 5 or more feet high and six or more wide. Plant accordingly. Once they are old enough to be tall, there is no way to make them short again.

This is the original Forever & Ever hydrangea.