Hydrangea Pruning Made Simple: A Species-by-Species Guide

Pruning hydrangeas doesn't have to be a guessing game. The secret? Know your species. Each of the five common garden hydrangeas flowers on either old wood (last year's stems) or new wood (this year's growth)—and that single fact dictates when and how to prune.

Know Your Hydrangea: The Big Five

Hydrangea paniculata – Panicle Hydrangea (e.g., 'Pee Gee', 'Limelight')

• Size: 8–10 ft tall and wide if unpruned.
• Hardiness: Zone 3–7.
• Blooms on: New wood (current season's growth).
• Flower form: Large, cone-shaped panicles, white aging to pink.

Hydrangea arborescens – Smooth Hydrangea (e.g., 'Annabelle', 'Hayes Starburst')

• Size: 3–5 ft tall, 5–7 ft wide.
• Native: Eastern North America.
• Blooms on: New wood.
• Flowers: Massive white mopheads, 10–12+ inches across.

Hydrangea macrophylla – Bigleaf Hydrangea (Mophead, Lacecap, 'Endless Summer')

• Size: 3–6 ft tall and wide.
• Flower color: Pink (alkaline soil) or blue (acidic soil).
• Blooms on: Old wood (previous season's stems). Exception: Rebloomers like 'Endless Summer' also flower on new wood.

Hydrangea quercifolia – Oakleaf Hydrangea

• Size: 6–10 ft tall, 8–12 ft wide.
• Advantage: Best drought tolerance of the group.
• Blooms on: Old wood.
• Forms: Single and double-flowered cultivars.

Hydrangea anomala subsp. petiolaris – Climbing Hydrangea

• Native: Woodlands of Japan and coastal China.
• Habit: Self-clinging vine to 50–80 ft with support.
• Blooms: Late June–early July, 6–10 inch lacecaps.
• Pruning: Rarely needed; trim only to contain spread.

Pruning Calendar: When to Cut

Species / Cultivar Group	Blooms On	Prune When	Notes
H. paniculata ('Pee Gee', 'Limelight')	New wood	Early spring (before growth starts)	Can cut back hard to 12–18" for larger blooms.
H. arborescens ('Annabelle', 'Hayes Starburst')	New wood	Early spring	Remove weak stems; shape as desired.
H. macrophylla (mophead, lacecap, 'Endless Summer')	Old wood (mostly)	Summer, before August	Deadhead spent blooms; remove only dead wood in spring.
H. quercifolia (oakleaf)	Old wood	Summer, before August	Prune after flowering to shape; avoid spring cuts.
H. anomala petiolaris (climbing)	Old wood	After flowering (July)	Only to control size; minimal pruning needed.

Pruning Basics

• Tools: Sharp bypass pruners; loppers or pruning saw for stems thicker than a pinky finger.
• Rejuvenation: On mature plants, remove up to ⅓ of oldest stems at ground level each year.
• Deadheading: Snip spent blooms anytime—this doesn't affect next year's flowers.
• Dead wood: Remove in early spring regardless of species.

Pro tip: If you're unsure which hydrangea you have, wait until it blooms. Cone-shaped panicles = paniculata or quercifolia (oakleaf has lobed leaves). Round mopheads or flat lacecaps in pink/blue = macrophylla. Huge white domes on a 3–5 ft shrub = arborescens. A vine = climbing hydrangea.

Stay tuned for Part III: winter protection, propagation, and preserving hydrangea flowers.

Photos courtesy University of Wisconsin Extension and Dave's Garden PlantFiles.