Hydrangeas are highly valued ornamental shrubs known for their abundant, showy flowers, making them a staple in many Northern California landscapes. Achieving a spectacular bloom display is directly tied to a proper pruning regimen. The mild, extended growing season in this region means that traditional pruning advice for colder climates often needs adjustment. Pruning timing depends on the local climate and the specific type of hydrangea being grown, requiring a tailored approach to ensure next season’s flower buds are not accidentally removed.
Identifying Hydrangea Types
Successful pruning begins with understanding the difference between hydrangeas that bloom on “old wood” and those that bloom on “new wood.” Old wood refers to stems grown during the previous season, while new wood describes fresh growth emerging in the current season. This distinction dictates the correct pruning time.
Hydrangeas that bloom on old wood set their flower buds on the previous year’s growth, typically in late summer or early fall. Common examples include the Bigleaf Hydrangea (Hydrangea macrophylla), which has mophead and lacecap varieties, and the Oakleaf Hydrangea (Hydrangea quercifolia). Pruning these types in late winter or early spring removes the buds that would produce flowers that summer.
In contrast, hydrangeas that bloom on new wood develop their flower buds on stems that grow in the current spring. This category includes the Smooth Hydrangea (Hydrangea arborescens), such as ‘Annabelle,’ and the Panicle Hydrangea (Hydrangea paniculata), including ‘Limelight.’ These types are forgiving with pruning, as the flower buds are not formed until the new season’s growth begins. Old wood is typically tougher, thicker, and grayish-brown, while new wood is softer, flexible, and often maintains a greenish tinge.
Optimal Pruning Schedule for Northern California
The mild climate of Northern California allows for an extended growing season, shifting the ideal pruning windows compared to colder regions. For hydrangeas that bloom on old wood, pruning must occur immediately after the flowering period ends to ensure the formation of next year’s buds. In this region, this usually means pruning should be completed by late summer or early fall, typically by mid-September.
Pruning later than this late summer window risks removing the microscopic flower buds developing for the following year’s display. The goal for old wood types is to only remove spent blooms and selectively thin out old canes, not to shape the shrub. The mild NorCal winter allows the dormant period to be used for removing dead wood, but major cuts should be avoided.
For hydrangeas that bloom on new wood, the pruning schedule is flexible and should be performed during the late winter dormancy period. This timing, usually between January and early March, is ideal because it occurs before the plant breaks dormancy and begins its new growth cycle. Panicle and Smooth hydrangeas tolerate hard pruning at this time, allowing for size management and encouraging strong, new stems that will bear summer flowers.
This late winter timing helps structure the plant before the growing season begins and avoids the risk of damage from harsh freezes, which are uncommon in Northern California. Pruning during this dormant window ensures the plant directs its spring energy into producing strong new growth for abundant summer blooms. Varieties like the ‘Endless Summer’ series bloom on both old and new wood; they can be lightly pruned anytime, but a clean-up in late winter is often simplest.
Essential Pruning Techniques
Several universal techniques are necessary for maintaining plant health and vigor, regardless of whether a hydrangea blooms on old or new wood. The most basic is deadheading, which is the removal of spent flowers. This can be done any time the flowers fade by cutting the stem just above the first set of healthy leaves or a visible growth bud.
The primary focus of any pruning session should be the removal of dead, diseased, or damaged wood (DDD), which can be done at any time of year, including the late winter dormant period. These dead canes should be cut back completely to the base of the plant. This prevents the spread of potential disease and opens the shrub for better air circulation. Any branches that are crossing or rubbing against each other should also be removed to prevent bark damage and entry points for pests.
For older, established hydrangeas that may have become spindly or overgrown, rejuvenation pruning can be applied. This process involves selectively removing the oldest and thickest canes right down to the ground level. To perform this technique correctly, no more than one-third of the total stems should be removed in any given year. This should be repeated over three years to gradually revitalize the shrub. Sharp, clean bypass pruners are the appropriate tool for making precise cuts, ensuring a clean wound that heals quickly and minimizes stress to the plant.