Hydrangeas: When to prune can vary

Pruning is a bit confusing on hydrangeas because it’s directly related to their bloom times. Plants that bloom on old wood should be pruned after they finish blooming. Plants that bloom on new wood can be pruned in the early spring.

In order to understand this, think about when the plant blooms. Plants that bloom in the early spring and summer are blooming on old wood that was formed last season.

Therefore, if you prune these types of plants in the spring, before they grow, chances are you are cutting off the flower buds.

Plants that grow in mid- to late summer typically bloom on new wood that grows this season. In this case, if you cut the plant back to the ground before it starts to grow in the spring, you are OK.

For those of you who have never had a hydrangea bloom and don’t know when it blooms, don’t do anything this year and see what happens.

Bigleaf and oakleaf hydrangeas bloom on last season’s growth. Therefore, if you are going to prune them, do it after they complete their blooms.

In many cases, these plants don’t require pruning unless they get overgrown or straggly.

If you are going to prune these plants, do it as soon after the flowers bloom as possible in order to reduce the risk of removing buds that are forming for the following season.

In addition, the earlier you do the pruning the quicker the shrub recovers and the larger the blooms the next season.

In some cases, when the blooms get smaller or the plant loses vigor, you may need to prune the older branches. Take these off at ground level.

The hydrangeas that bloom in the summer (panicles and smooth) produce their flower buds on growth that comes out this season.

If you need to prune these plants, cut them back in the early spring. I find that cutting them back to the ground produces bigger flowers on shorter, sturdier stems.

If you have been pruning properly and still don’t have blooms, then there is something else going on.

Terminal (at the tips of the stems) flower buds sometimes get killed by the cold, especially if the plants are exposed. Sometimes when this happens, the lateral buds along the branches bloom and are normally much smaller.