Learning to trim unhealthy and unruly growth on a plant is an important part of having a productive garden. When and how to prune hydrangea is a source of concern to many home gardeners who worry they'll kill the plant. Here are some steps to follow to ensure proper hydrangea pruning.
Step 1 - Determine Type Of Hydrangea
Different types of hydrangea have different pruning requirements, so it's important to first determine which variety is in your garden before attempting to trim it. Popular garden types are Bigleaf, Mophead, and Lacecap. These flower in mid to late summer on shoots that grew the previous year. Types that flower on new growth include Oakleaf, Arborescens, and Paniculata. Another type, the climbing hydrangea, is actually a vine, not a bush, and requires little to no pruning.
Tip: If your hydrangea finishes flowering in mid-late summer, it "blooms on old wood." You'll want to prune this type in late summer. If your hydrangea blooms in late summer through the fall, it "blooms on new wood." You'll cut these back in late winter, before any new growth is seen.
Step 2 - Prune After Blooming
Bigleaf, Mophead, and Lacecap, since they bloom on the previous year’s growth, should be pruned after blooming when the plant goes dormant or all the leaves fall off. Depending on climate zone, this is generally late fall. These types of hydrangea can also be pruned in the early spring before new growth begins. This is the preferred time if the area is subject to harsh winter temperatures.
Prune old flowerheads to the first pair of strong, healthy buds. More pruning can be done on mature, established hydrangea bushes to remove older stems and encourage new growth from the plant’s base. Remove all dead canes by cutting them down to the ground. If the plant is more than three years old, thin out the branches by removing 1/3 of the oldest canes, again cutting to the ground. Remove any old flowerheads that remain as well. Remember that any green buds removed at this time could have been more flowers, so keep in mind whether the goal is more flowers or a neater plant.
Step 3 - Prune Oakleaf, Paniculata, and Arborescens Hydrangea
In order to ensure a new crop of sturdy stems, Oakleaf, Paniculata, and Arborescens hydrangea should be pruned in early spring. Cut stems back in February or March, either to near ground level or even with the hydrangea’s main trunk. Sturdy stems are required to ensure masses of blooms at the ends of arching stems. In the fall and winter, do not trim or prune off the old flowerheads, as they will still look attractive throughout this time.
Step 4 - Prune Pee Gee Hydrangea
Some gardeners like to train the Pee Gee hydrangea to become a small tree by removing 1/3 of the plant’s lateral small branches from the ground up. This should be done in late winter or early spring. After these branches are pruned off, cut away any crossed branches or those that aren’t growing away from the middle of the plant.
Although Pee Gee hydrangeas can be cut to any size between six inches and three feet tall each year, it’s best to plant this in a location where it’s free to grow large. Don’t prune hard to the ground in this case, as gentle pruning will be what keeps the plant healthy and encourages new growth.