Hydrangea How-To

I devoted my column in today's Newsday to answering readers' questions. But there's never enough space on the printed page. So I thought I'd use my blog to answer a few more.

A lot of you are worried about your hydrangeas. Sue Cavanaugh of Northport has a 5-year-old variegated lacecap that has never bloomed. She reports that it gets mid-to-late afternoon sun and grows beautiful leaves but no blossoms. “I have tried cutting it back in the fall,” she writes, “another year I left it and did no trimming.” Either way, no flowers.

Roberta Schwartz’s hydrangeas grow robust in hot mid-day sun as well but they, too, are flower-less. “I don’t fertilize them because I believe that will just make them larger,” she writes in her email.

Roberta is right, of course. Fertilizers promote growth, not necessarily flowering and if there’s a lot of nitrogen in the soil you may never see a bloom. So a good place to start is with a pH test. You can contact your local Cooperative Extension office – they’re a gardener’s best friend, especially in times of trouble.

So what is it about hydrangeas that causes such anxiety? We certainly can’t live without them – at least I can't. But how do we live with them? In all my years as a garden columnist, I get more questions about hydrangeas than any other plant. I don’t have all the answers but there are some things I can tell you. They prefer morning or early afternoon sun and dappled – not deep – shade when the day gets really bright. Watering is critical when they're flowering and when they set their buds in July and August. Hydrangeas like moist, well-drained, humus-rich soil. So make sure you put them in the right spot. By the way, September is the perfect time for planting.

You have to know what kind of hydrangeas you have if you want to get the most out of them. Lacecaps and mopheads shouldn’t be cut back too often and especially not in fall. That's because they flower on year-old growth and older wood. Dead branches can be removed in spring. Or you can prune right after bloom-time to shape the plant. Make sure you cut back to strong, fat flower buds. A good way to keep your Hydrangea macrophylla looking good is to prune out one-third of the older stems as well as any that are twisted or turning inward where they won't be able to develop properly. New shoots will grow and the additional light and air will turn the bush into a bouquet.

As they age, hydrangeas can become a mass of weak scraggly stems that produce fewer and fewer flowers -- especially if you haven't kept up with routine pruning. That's when they might need an overhaul. You can rejuvenate your hydrangea by cutting it down to about six inches from the ground in late winter. The jobs requires sharp long-handled loppers, nerves of steel and a little faith -- you’ll be sacrificing flowers but it's a necessary sacrifice.

Oakleaf hydrangeas burst into bloom on the previous season’s growth and don’t need regular pruning. What a relief. But it’s okay to thin weak wood in the spring or after the shrub flowers. Peegees do their thing on new wood so you can prune hard in early spring before growth begins.

As for pink versus blue flowers. It's true that pink blossoms indicate alkaline soil while blue blooms signify acidic conditions. But to me, it hardly seems worth the trouble of amending your soil to just change the color of a flower. Besides, I like it when the blooms turn maroon and brown in fall and the bush becomes like a giant dried floral arrangment.

Regardless of their hue, I think hydrangeas are heavenly.