Tips For Hydrangea Care

One of the most common questions I get asked between June and September is “How do I prune my hydrangeas and when?” My answer is always the same. “It depends,” I say.

If you go by the adage to prune summer flowering shrubs in the spring, you’re in for big trouble. The answer to the “when” part generally relates to the type of hydrangea you have. We can whittle down the choices to six types that fall into only two pruning groups. Except for the exceptions, and you knew that was coming. And since none are done now, you can relax and figure out what types you have.

But then there’s the other question. Why do you want to prune them? Some people seem to think that pruning these shrubs is necessary to get them to rebloom and this isn’t necessarily true. Again, it depends on the type you have.

Another reason is to reshape a plant that has grown too large or for some reason has grown out of shape. And a third reason might be to prune a plant that has been damaged by winter snow, an ice storm, or as a result of heavy deer browsing.

The one thing you don’t want to do is any heavy pruning of your hydrangea at the peak of its growing season. Doing this removes so much foliage that the plant’s ability to replace roots and store carbohydrates in the root zone, which is necessary for winter survival, is dramatically and sometimes fatally, reduced.

First we need to dispel some time-honored but possibly erroneous pruning advice concerning the practice of deadheading. It’s a common practice for gardeners to deadhead hydrangea macrophylla, or the lacecap hydrangea, as the flowers fade.

The common wisdom has been that if you allow the spent blooms to remain on the plant that this protects the buds of next year’s flowers that are present along the existing stem during the winter. Ah, but the fact of the matter is that as the spent flowers deteriorate from late fall into the winter, they naturally fall off and next year’s flowers seem to survive.

The larger question may be if by removing this year’s spent flowers, are you allowing the shrub to spend more of its energy in producing buds and roots instead of sending that energy into seed production? This would, in theory, result in a more winter-hardy plant with more survivable buds for next year’s show, thus supporting the deadheading practice.

Then there is cleaning-up pruning, which involves the removal of any shoots that didn’t harden off by winter and were damaged by late fall hard frosts, the ravages of winter, or a severe early spring frost. These damaged shoots should be cut back to new vigorous growth in early spring as soon as the threat of hard freezes have passed and new growth begins to be obvious.

If the shoot shows no signs of life, then simply cut it down to the ground. You can also remove some of the central shoots that may look quite nice but some thinning of these shoots may allow more sunlight and air the reach the center of the plant. The new stems that emerge as a result of your pruning will likely not flower that season, but will the following year.

Rejuvenative pruning is the last, but probably the most important type, of hydrangea pruning. This is where most of the questions come up. A young hydrangea may need a snip here or an errant shoot removed there, but a larger, older hydrangea may be in need of much more serious attention to bring it back to life or to get it back into shape.

As a general rule, a large and mature hydrangea should be reduced by as much as 1/3 every couple of years by removing the oldest wood. This allows light to penetrate into the center of the shrub, which encourages new replacement limbs. This type of major pruning can be done during our traditional January thaw or on a warm day in February when the plant structure is very visible and there’s no danger of cutting new shoots.

Even if a large and mature hydrangea becomes badly damaged from snow falling off a building or in an ice storm, there’s still hope. The solution is dramatic but in most cases it works. Cut the shrub down to 18 inches to 2 feet late in the winter or early in the spring. This drastic pruning will mean no flowers for that season but beginning the following season, the shrub will begin flowering again and will take on a more noticeable shape with a new framework and new branches.

Now there are some of us who have hydrangeas that we wish had flowers to prune. If you have another home in the Catskills, Berkshires or further up in New England, you may get wonderful foliage each year but few if any flowers.

I’ve been trialing five hydrangeas in my Zone 5 garden and if I’m very, very lucky I may get one or two reluctant flowers. This may also happen out here in severely cold winters, especially around the Pine Barren areas where it can often go below zero.

But I think I have a solution.

Last fall, as the leaves fell off one of my perpetual non-bloomers, I built a chicken-wire cage around the stem structure. The cage was about 30 inches in diameter and 4 feet tall.

As the leaves fell off one of my maple trees I let them dry out and get slightly crispy. Then over a period of weeks, I filled the cage with maple leaves. Inevitably the leaves compressed and filled only two-thirds of the cage, but my hope was that the maple leaves would insulate the stems just enough to save them and their buds from the ravages of months of wicked cold.

In late March and through early April I very slowly removed the leaves to reveal healthy stems covered with swelling buds. Some of the stems did die back a bit so I pruned back to the first swelling bud. To my amazement, the experiment worked.

For the first time in eight years. I have a 5-foot-tall hydrangea covered with dozens of blue flowers. Approximately 60 feet away, the other hydrangeas that weren’t caged are half the size, have lush foliage, and not a single flower.

Next week, the specifics for the various groups, some tricks, of course, and how in the world do you handle these new alleged everblooming varieties like Fantasy and Forever and Ever?

Keep growing.