Are Hydrangeas Annuals or Perennials? A Guide to Their Growth Cycle

With their voluminous blooms in shades of pink, blue and white, hydrangeas are a quintessential addition to many gardens. But before planting them, it’s helpful to understand whether hydrangeas are annuals or perennials. Knowing the life cycle and growth habits of these popular shrubs can ensure you choose suitable varieties and care for them properly year after year.

The Short Answer

Hydrangeas are perennials. With proper care, they can thrive for decades in the garden going dormant in winter and re-blooming every spring and summer. There are some exceptions based on climate suitability that we’ll cover but in general, hydrangeas are long-living woody plants.

Annuals vs. Perennials vs. Biennials

Before diving further into hydrangeas, let’s review the difference between annual, perennial, and biennial plants:

• Annuals complete their entire life cycle in one season. They germinate, flower, set seed, and die all within a single growing period. Common annual flowers include petunias, marigolds, and zinnias.

• Perennials persist for many years. They go dormant in winter then re-sprout the following spring. Perennial plants often have woody stems that don’t die back. Examples include peonies, coneflowers, and hydrangeas.

• Biennials take two years to complete their life cycle. They typically form foliage and roots the first year, then flower, set seed, and die the second year. Examples are foxglove and hollyhocks.

Perennials are the longest living of the three groups. And that’s exactly how hydrangeas behave.

USDA Hardiness Zones for Hydrangeas

Most hydrangeas are cold hardy to USDA zones 3-9. This makes them perennial through most areas of the U.S. Specific varieties have slightly different hardiness:

• Bigleaf hydrangeas (Hydrangea macrophylla): Zones 6-9
• Oakleaf hydrangeas (Hydrangea quercifolia): Zones 5-9
• Panicle hydrangeas (Hydrangea paniculata): Zones 3-8
• Smooth hydrangeas (Hydrangea arborescens): Zones 3-9

Gardeners in the warmest and coldest zones may have trouble growing hydrangeas. But across the majority of the country, they will thrive year after year.

Can Hydrangeas Be Grown as Annuals?

In climates where hydrangeas aren’t winter hardy, they can be treated as annuals. For example, gardeners in zones 10 and up would need to replace their plants each year.

You can also grow hydrangeas in containers and bring them indoors over winter. Just be sure to gradually acclimate them when moving them in and out to prevent shock.

Buying potted hydrangeas from florists and nurseries is another way to enjoy them as annuals. The plants are not intended to survive long term in these cases.

So while hydrangeas are perennial shrubs at heart, gardeners in fringe climates do have some flexibility in growing them temporarily as annual flowers.

Signs Hydrangeas Are Perennials

Here are some clear signs that hydrangeas are herbaceous perennials:

• Woody stems – Unlike true annuals, hydrangea stems persist over winter and regrow in spring from the same roots and crowns.

• Regrowth – Well-established plants bloom faithfully each year without needing to be replanted. They go dormant in fall and winter.

• Flowering – Blooming on both old and new wood is a trait of perennials. Annuals only bloom on new season growth.

• Lifespan – With proper care, hydrangea shrubs live for many years. Some remain beautiful for decades.

• Cold tolerance – Their ability to withstand freezing winter temperatures in zones 3-9 demonstrates hydrangeas are not annuals.

• Pruning – Pruning and deadheading practices focus on maximizing flowers year after year versus just a single season.

Caring for Hydrangeas as Perennials

The main steps for success with perennial hydrangeas include:

• Select winter hardy types for your growing zone.

• Plant in spring or fall to establish extensive root systems.

• Situate in partial shade or morning sun locations.

• Provide moist, well-draining soil. Amend clay or sandy soils at planting time.

• Add protective winter mulch in cold areas after the ground freezes.

• Prune judiciously based on the blooming habits of the variety.

• Water 1-2 inches per week in summer, less in other seasons.

• Feed with slow release or liquid fertilizer to maintain flowering.

• Leave spent blooms on plants over winter to protect bud development.

• Divide crowded, overgrown plants in early spring every 3-5 years.

With the right care, hydrangeas will flourish for years as easy-care perennials. They ask relatively little once established compared to true annuals.

Special Considerations by Variety

The main hydrangea species and cultivars have some unique perennial care needs:

Bigleaf Hydrangeas

• Bloom on old wood so avoid heavy pruning in fall or spring.

• Can adjust flower color based on soil pH.

• Benefit from winter protection in colder zones.

Oakleaf Hydrangeas

• More cold tolerant than other types.

• Produce flowers on new wood each year.

• Require occasional rejuvenation pruning.

Smooth Hydrangeas

• Native American species good for naturalized areas.

• Tolerant of partial shade.

• Respond well to hard pruning when overgrown.

Panicle Hydrangeas

• Two types: mopheads bloom on old wood, lacecaps on new.

• Lacecaps need annual pruning, mopheads just shaping.

• Provide strong support for top-heavy stems.

Climbing Hydrangeas

• Need a sturdy trellis or structure for clinging stems.

• Bloom best in dappled sun or light shade.

• Prune immediately after flowering finishes.

Annual Hydrangeas are Possible

At the end of the day, the vast majority of hydrangea shrubs are undeniably herbaceous perennials. But gardeners can push the limits and grow them as annuals in zones with extremely hot summers or frigid winters. Container culture also lends itself to temporarily enjoying hydrangeas as annual plants.

No matter which route you choose, understanding hydrangeas’ perennial nature will set you up for success. With the right variety and proper care, these gorgeous bloomers will grace your garden every year for seasons to come.