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GARDENING

A passion for hydrangeas

A friend was commenting on the questions I get on TV. He said, “Why don’t you just get the hydrangea questions over with right up front?” I laughed. He’d nailed it.

The most-asked gardening question, for me and nursery staff, is “Why doesn’t my hydrangea bloom?” Second in popularity is “When do I cut back my hydrangea?”

All that turned me off hydrangeas for a while. I wondered why all the fuss—the zillion new cultivars, the big obsession, whole sections in garden centers dedicated to them. Maybe I even called them gaudy, blowsy, ostentatious. But then I fell in love.

It was ‘Pinky Winky’ that touched me first—perky upright plant, huge white cones that turn to blush. Then came the elegant ‘Limelight’ and ‘Little Lamb,’ followed by ‘Lady in Red’ with her gorgeous lacecap flowers and colorful stems. Now I get it.

So let me share the joy.

Why don’t they bloom?
If your hydrangea doesn’t bloom, we need to first rule out one possibility. Are you cutting it back in fall, when it’s one of the kinds that blooms on old wood? If so, it already started those buds in late summer—so you cut your flowers off.

Here’s the rule: Don’t prune mophead, lacecap, or oakleaf hydrangeas after July.

Most of the time, however, the failure to bloom has to do with bud hardiness. Most plants on the market are hardy to Zone 5 or even Zone 4. They live through our cold winters and produce abundant, lush foliage. Unfortunately, the buds aren’t so hardy. A late spring frost or freezing night, after a warm spell, zaps those buds and it’s over. No flowers this year.

This happens most often to some Hydrangea macrophylla (mopheads), such as ‘Nikko Blue,’ one of the first that became commonly available in the trade. Only some mophead cultivars do get nipped in the bud, and maybe you can do something about it (or choose other cultivars).

While we can’t control weather, we can take steps to protect the most fragile hydrangea buds. When the frost is coming in April or May, we can cover our plants with tarps, sheets, tents, or the Shrub Coat™ (a commercial product developed for this purpose). Or, if we covered our hydrangea for the winter, we could leave the cover on until the May freezes are over. (You do need to remove opaque covers such as burlap to give the plants some light.)

Whether or not you’ll do all that, or catch on when a frost is coming, is dubious. So maybe it would be better to straighten out which hydrangeas to choose, i.e., those that do bloom in WNY without any trouble. Really safe bets are ‘Endless Summer’ and its followers. They represent a whole line of cultivars developed in recent years that bloom on both old and new wood so you will have blooms no matter when there’s a frost (or even when you prune them). For smaller gardens, a reliable line of repeat bloomers is the ‘Let’s Dance’ series, including ‘Starlight.’

Types of hydrangeas and their pruning
In order to answer that pruning question, you need to know what kind you have. If you lost the plant tag, or your hydrangeas came with the house, you can still sort out the species (if not the cultivar) and learn what to do. (These are only the basics, however. Hydrangea identification and nomenclature is complicated and there are many hundreds of possible cultivars out there; for more detailed information see Hydrangeas for American Gardens by Michael A. Dirr; Timber Press, 2004.)

Mopheads and lacecaps: The flowers are round (Hydrangea macrophylla, mopheads) or flat (H. macrophylla normalis, lacecaps) and open up blue, pink, or purple. The lacecaps have buds in the middle and bold florets around the outside. The four- or five-inch leaves are heart-shaped, thick, and shiny, with jagged edges. These are the flowers that turn blue or pink, according to the soil pH. In alkaline soil, they will be pink; in acid soil, they will be blue. If you have a color preference you can purchase products to change the pH, slowly. Many people attempt to produce blue flowers with acidifying fertilizer products (Miracid), but they are only a quick fix. Ultimately, you must change the soil pH to accomplish the goal.

Pruning: You do not need to prune mopheads or lacecaps except to cut out dead stems. If you want a more compact plant, you should cut it back before August. If you have an older plant (over five years), you can revitalize it by taking out one-third of the old stems from the bottom of the plant each year.

Oakleaf hydrangeas are named for the shape of their leaves (four to ten inches long). They turn a rich wine or maroon color in fall and have large white flowers that turn slightly pink. They are my favorite shrub, and I am not alone among landscapers. They die back nearly to the ground in very cold locations, so place them where this won’t bother you; they’re worth waiting for. Little pruning is needed; treat the same as mopheads.

Smooth hydrangeas (H. Arborescens) are native plants that flower reliably on new wood. Most people know them as ‘Annabelles’ or ‘Grandiflora’ and choose them for the snowball-like flowers, which open up greenish and turn white. They often flop over, but newer cultivars (‘Incrediball’) are entering the market, hybridized to develop stronger stems. The species is a good selection for naturalized landscapes.

Prune these plants anytime except in spring or early summer before they bloom. If you cut them back drastically after the blooming period, you may get a dramatic regrowth (often done for hedges), but the stems will not have time to get stronger and may be especially floppy that season.

Panicle hydrangeas have cone-shaped or round flowers that start out white and often turn pink, and leaves that grow in whorls of three. You might know ‘Tardiva,’ ‘Pink Diamond,’ Chantilly Lace,’ and ‘Pinky Winky.’ My friend, Joan Mariea (the “Queen of Hydrangeas” to those who know her and have heard her hydrangea talks), recommends panicle types as the easiest for beginners to grow. You can prune them in fall, winter, or early spring but it’s not necessary; just cut crossing or unattractive branches. They bloom dependably on new wood, and fill the summer garden with dramatic blossoms.

When I asked her to name her favorite hydrangeas, Mariea started with ‘Limelight’ (a panicle type with huge green-tinted blossoms that don’t flop), and added ‘Pink Diamond’ (upright, perky, with rich dark pink flowers). She went on to recommend ‘Little Lamb’ for the mounding habit, and ‘Pinky Winky’ for the three-toned effect. She would have gone on and on.

“But Joan,” I insisted. “Stop! I’m begging you ... Just name one best one for the people.”

“Oh no! They’re all my babies.” She laughed with her characteristic laugh, wriggling out of it. “I could never pick just one hydrangea!”

And I couldn’t, either.

Sally Cunningham (CNLP) is an author, lecturer, Channel 4 (WIVB) garden expert, and consultant for Lockwood’s Greenhouses.