Garden Detective

Garden Detective: Hydrangea looks healthy but where are flowers?

Our hydrangea bloomed beautifully three years ago. Last year, we had only three blooms. This year, we’ve seen no buds. We have followed the directions for pruning down one third. The plant looks very healthy and large! Please help with any suggestions. It gets great sun exposure and plenty of water.

D.J. Wright, El Dorado Hills

Hydrangeas can be a little tricky. Lack of flowers almost always can be traced back to pruning – either at the wrong time or the wrong branches.

There are many types of hydrangeas, say UC master gardeners, and the timing of the pruning depends upon whether the hydrangea blooms on current or previous years’ growth.

The mophead varieties – Hydrangea macrophylla – are the most common and have large, globe-shaped flowers. Judging by the photo you enclosed, this is your type of hydrangea. These bloom on previous years’ growth or “old wood.” Pruning in late fall or early winter will eliminate the bloom for next spring.

But they won’t bloom again on a branch that has already bloomed. So, the solution is to prune in late summer when the flowers start to fade.

Branches that bore flowers should be cut to within a foot of the ground or cut back so that only two to four buds remain on the branch. This is done in the hope that some of these buds will grow into branches before the plant goes dormant. And since these kinds of hydrangeas flower on wood that grew in the previous year, there is thus potential for more flowers next spring.

Many gardeners prune hydrangeas a second time in January because, while the plants are out of leaf, it is easier to identify and eliminate crossing branches and old wood. Removing old wood makes more room for new branches to sprout from the crown of the plant.

The important point to remember is that they bloom on the growth that grew the prior season but didn’t flower.

Hydrangeas need little pruning except to deadhead or to remove dead stems. To encourage a particular shape, prune right after your bush blooms.

Older hydrangeas may benefit from some rejuvenation pruning. (This is the “one third” you mentioned.) This involves removing about one-third of the older stems down to the ground to allow light to penetrate to the center of the shrub and to encourage replacement limbs. This can be done in the summer or in the winter, at the expense of some blooms. Pruning by a third will eliminate some blooms the next spring and does not need to be done every year.

Fertilizing usually is not necessary, but the plants will respond to an application of a slow-release, balanced fertilizer during the spring growing season. Apply per label instructions. With your plant, you may want to give it a little bone meal to prompt blooms, too.

Mulching is a good practice as it helps hold in moisture around the roots and the decaying organic matter adds nutrients to the soil. Those will also benefit blooms.

You may have no blooms this year, but your bush likely is primed to have a lot of flowers next spring. Just give it a year off from pruning and see what it does.

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