Are Hydrangeas Annuals or Perennials?
While hydrangeas are perennials, their ability to return each spring depends on key factors like climate and variety selection, influencing their survival.
For many new gardeners, a common question about hydrangeas is whether they will last for a single season or return each year. This uncertainty about their lifecycle can be a point of confusion. Understanding if these shrubs are a short-term plant or a long-term garden feature is important for their care and success.
The Annual vs. Perennial Question Answered
Hydrangeas are classified as perennials. More specifically, they are deciduous, woody perennials, meaning their stems are tougher and more bark-like than those of herbaceous perennials. An annual plant completes its life cycle within a single growing season, while a perennial lives for more than two years, regrowing each spring from its existing root system.
A hydrangea’s life cycle involves active growth and flowering throughout spring and summer. As autumn arrives and temperatures drop, the plant enters dormancy and sheds its leaves. Though it may appear lifeless during winter, the roots and woody structure are still alive. In the spring, new growth emerges, and the cycle begins again, with some hydrangeas living for as long as fifty years.
Understanding Hydrangea Hardiness
A hydrangea’s ability to survive the winter depends heavily on the local climate. The USDA Plant Hardiness Zone map helps with this by dividing North America into zones based on average annual minimum winter temperatures. This system helps gardeners select plants that can tolerate their region’s coldest temperatures.
Different hydrangea species have varying levels of cold tolerance. Panicle hydrangeas (Hydrangea paniculata) are tough, thriving in zones 3 through 8. Bigleaf hydrangeas (Hydrangea macrophylla) are less cold-hardy and recommended for the more moderate zones 5 through 9. Oakleaf hydrangeas (Hydrangea quercifolia) are also suitable for zones 5-9. Planting a variety suited to your specific zone is a primary factor in its long-term survival.
Why a Hydrangea Might Not Return
Sometimes a hydrangea fails to return after winter, leading to the mistaken belief that it was an annual. One common reason is the “florist hydrangea.” These are typically Bigleaf hydrangeas cultivated in greenhouses to force them into bloom out of their natural season, such as for holidays like Easter. These plants are not bred for garden hardiness and lack the root systems needed to survive a winter outdoors.
Another reason for failure is planting a variety outside its recommended hardiness zone. For example, a Bigleaf hydrangea in a zone 4 garden is unlikely to survive the winter without protection. Extreme weather, like a deep freeze after new growth has started in the spring, can also damage or kill an established plant.
Improper pruning can also prevent a hydrangea from reblooming. Some species, like the Bigleaf hydrangea, bloom on “old wood,” meaning flower buds form on the previous year’s stems. If a gardener prunes these stems in the fall or early spring, they are removing the potential flowers for the upcoming season.