The Times to Prune Hydrangeas

The best time to prune depends on the type of hydrangea.

Hydrangeas bear striking, round clusters of white, pink, lavender or blue flowers throughout the summer in warm, moist climates. These woody shrubs are a favorite for foundation planting, edgings and garden beds. Hydrangeas generally don't need pruning unless they are older or damaged from storms or other problems. The best time to prune hydrangeas depends on whether flowers bloom on old growth or new growth.

Identification of Your Hydrangea

Before you consider pruning your hydrangea shrub, it is important to know what type of hydrangea you have. Some hydrangeas flower on old growth, that is, on stems that grew during the previous growing season. Other varieties grow on new growth, which are stems that grew during the current season. If you prune incorrectly, you will destroy the branches that will produce flowers this year. To identify your hydrangea, look closely at the shrub. Mophead hydrangeas are the type that have serrated leaves and are vivid pink and blue, depending on soil acidity and alkalinity. Lacecap are also pink or blue, with a flatter, spreading flower. Oakleaf hydrangeas have oakleaf-shaped leaves and bloom in white. These varieties produce their flowers on old wood. PeeGee and Annabelle hydrangeas are both white varieties and bear their flowers on new wood.

Pruning on Old Wood

Mophead, lacecap and oakleaf hydrangeas generally produce buds in August, September and October for the following year's flowers. This type of hydrangea should only be pruned in June or July. Remove all dead or broken stems. If the plant is over 5 years old, cut it back 1/3 of the way to revitalize growth. If the plant is too large, cutting it back at this time will not hurt the next year's blooms.

Pruning on New Wood

PeeGee, also called panicula, and Annabelle types of hydrangea produce flowers on the current year's growth. PeeGee types should not be pruned in summer when they are preparing to bloom. Annabelle types should not be pruned in spring. Cut back Annabelle varieties just enough to improve the size and appearance. Too much pruning will prevent the stems from properly supporting the large flowerheads. According to Danny Lipford, PeeGees do not need pruning at all, but if you choose to prune them to improve their appearance, do it after the flowers bloom. They are the only type of hydrangea that can be pruned into a tree shape, if desired. This is achieved by leaving the trunk section and top branches unpruned.

Deadheading

Deadheading is not the same as pruning. Deadheading is the removal of old blooms that have dried up and are still on the shrub. You can remove these at any time when flowers fade without injuring the plant.

References

• Hydrangeas Hydrangeas: Pruning Made Easy
• Danny Lipford: When to Prune Hydrangeas
• North Carolina State University: Pruning Hydrangeas