How to Prune Hydrangeas
The most frequently asked question we get in spring is “How do I prune my hydrangeas?” With 80 distinct species and hundreds of cultivated varieties, it is not surprising that pruning hydrangeas strikes fear in the hearts of some gardeners everywhere. Thankfully, there are only six species we deal with in the Midwest, and once you know which one you have, pruning becomes much easier. When purchasing a hydrangea, it is a good idea to hang onto the nursery tag that shows the species and variety, so come pruning time, you will be well prepared.
New Wood vs. Old Wood vs. Old and New Wood – Say What?
You may hear the terms “blooms on new wood” or “blooms on old wood.” With hydrangea, some varieties bloom on old wood and some on new wood, meaning you cannot apply the same pruning method to all of them. This is an important aspect, as it will help guide when to prune. So, what is the difference?
New Wood - Hydrangea that bloom on new wood form flower buds in spring. Stems emerge during the current growing season, and buds form on this new growth. Panicle Hydrangea (Hydrangea paniculata) and Smooth Hydrangea (Hydrangea arborescens) bloom on new wood.
Old Wood - Hydrangea that bloom on old wood create flower buds for the next year shortly after they finish blooming. Bigleaf Hydrangea (Hydrangea macrophylla), Mountain Hydrangea (Hydrangea serrata), Climbing Hydrangea (Hydrangea petiolaris), and Oakleaf Hydrangea (Hydrangea quercifolia) bloom on old wood.
Old and New Wood – Wait, what? Just to keep you on your toes, some older varieties of Hydrangea macrophylla only bloom on old wood, while newer reblooming varieties (Hydrangea macrophylla x serrata) bloom on both old and new wood. It is important to know which variety you have so you can prune properly. The nursery tag should give you this information, so don’t throw it away!
New Wood vs. Old Wood vs. Old and New Wood – Say What?
You may hear the terms “blooms on new wood” or “blooms on old wood.” With hydrangea, some varieties bloom on old wood and some on new wood, meaning you cannot apply the same pruning method to all of them. This is an important aspect, as it will help guide when to prune. So, what is the difference?
New Wood - Hydrangea that bloom on new wood form flower buds in spring. Stems emerge during the current growing season, and buds form on this new growth. Panicle Hydrangea (Hydrangea paniculata) and Smooth Hydrangea (Hydrangea arborescens) bloom on new wood.
Old Wood - Hydrangea that bloom on old wood create flower buds for the next year shortly after they finish blooming. Bigleaf Hydrangea (Hydrangea macrophylla), Mountain Hydrangea (Hydrangea serrata), Climbing Hydrangea (Hydrangea petiolaris), and Oakleaf Hydrangea (Hydrangea quercifolia) bloom on old wood.
Old and New Wood – Wait, what? Just to keep you on your toes, some older varieties of Hydrangea macrophylla only bloom on old wood, while newer reblooming varieties (Hydrangea macrophylla x serrata) bloom on both old and new wood. It is important to know which variety you have so you can prune properly. The nursery tag should give you this information, so don’t throw it away!
PROPER PRUNING STARTS WITH KNOWING YOUR PLANT
Smooth Hydrangea (Hydrangea arborescens)
Zones: 3-9 | Origin: Native to North America
Blooms on: New Wood
Flower type: Round with white, white/green, or pink blooms
Light: Part shade (morning sun with afternoon shade)
Popular Selections: ‘Annabelle’, Incrediball, and Invincibelle series
Pruning: Late winter / early spring. Cut all stems to 6-12″ tall.
Zones: 3-9 | Origin: Native to North America
Blooms on: New Wood
Flower type: Round with white, white/green, or pink blooms
Light: Part shade (morning sun with afternoon shade)
Popular Selections: ‘Annabelle’, Incrediball, and Invincibelle series
Pruning: Late winter / early spring. Cut all stems to 6-12″ tall.
Annabelle Hydrangea
Bigleaf Hydrangea (Hydrangea macrophylla)
Zones: 4-9 | Origin: East Asia
Blooms on: Old wood (older varieties); old and new wood (reblooming varieties)
Flower types: Mophead/lacecap; color shifts with soil pH (pink in alkaline soil, blue in acidic)
Light: Part shade (morning sun with afternoon shade)
Popular Selections: Endless Summer series (Bloomstruck, Twist-n-Shout, Summer Crush), and Let’s Dance and Seaside Serenade series
Pruning:
Blooms on old wood: Prune in summer or early fall after plants have finished flowering. Remove dead and/or weakened stems, cutting them to the ground.
Blooms on new and old wood: Pruning generally isn’t needed since they bloom on both old and new growth; however, you can remove old flowers and take out dead or weak stems in the spring.
Zones: 4-9 | Origin: East Asia
Blooms on: Old wood (older varieties); old and new wood (reblooming varieties)
Flower types: Mophead/lacecap; color shifts with soil pH (pink in alkaline soil, blue in acidic)
Light: Part shade (morning sun with afternoon shade)
Popular Selections: Endless Summer series (Bloomstruck, Twist-n-Shout, Summer Crush), and Let’s Dance and Seaside Serenade series
Pruning:
Blooms on old wood: Prune in summer or early fall after plants have finished flowering. Remove dead and/or weakened stems, cutting them to the ground.
Blooms on new and old wood: Pruning generally isn’t needed since they bloom on both old and new growth; however, you can remove old flowers and take out dead or weak stems in the spring.
Summer Crush Hydrangea | Image: First Editions
Panicle Hydrangea (Hydrangea paniculata)
Zones: 3-8 | Origin: East Asia
Blooms on: New wood
Flower type: Cone-shaped white blooms that may turn pink in fall
Light: Full sun to part shade
Popular Selections: A species with the most varieties – more than 265 to date and more every year. Bobo, Berry White, Fire Light, Limelight, Pinky Winky, Quick Fire, Vanilla Strawberry, and the Little series (Little Lime, Little Hottie, Little Quick Fire)
Pruning: Late winter / early spring. Cut all stems down to be between 6-12″ tall.
Zones: 3-8 | Origin: East Asia
Blooms on: New wood
Flower type: Cone-shaped white blooms that may turn pink in fall
Light: Full sun to part shade
Popular Selections: A species with the most varieties – more than 265 to date and more every year. Bobo, Berry White, Fire Light, Limelight, Pinky Winky, Quick Fire, Vanilla Strawberry, and the Little series (Little Lime, Little Hottie, Little Quick Fire)
Pruning: Late winter / early spring. Cut all stems down to be between 6-12″ tall.
Spring Sizzle Hydrangea | Image: First Editions
Climbing Hydrangea (Hydrangea petiolaris)
Zones: 4-8 | Origin: East Asia
Blooms on: Old wood
Flower type: White lacecap blooms
Light: Part shade to full shade
Popular Selections: Firefly, Miranda, Silver Lining
Pruning: Prune in summer or early fall after plants have finished flowering. Remove dead, damaged, or diseased growth and lightly shape plants as needed. If plants become overgrown, trim back to the desired size.
*Note: Woody vines cling to structures with aerial roots without support, but they benefit from initial training to help them grow in the proper direction. Plants will eventually cling on their own without additional support. They can also spread as a groundcover if untrained. This species is vigorous and can quickly cover a structure.
Zones: 4-8 | Origin: East Asia
Blooms on: Old wood
Flower type: White lacecap blooms
Light: Part shade to full shade
Popular Selections: Firefly, Miranda, Silver Lining
Pruning: Prune in summer or early fall after plants have finished flowering. Remove dead, damaged, or diseased growth and lightly shape plants as needed. If plants become overgrown, trim back to the desired size.
*Note: Woody vines cling to structures with aerial roots without support, but they benefit from initial training to help them grow in the proper direction. Plants will eventually cling on their own without additional support. They can also spread as a groundcover if untrained. This species is vigorous and can quickly cover a structure.
Climbing Hydrangea
Oakleaf Hydrangea (Hydrangea quercifolia)
Zones: 5-9 | Origin: Native to the southeastern US
Blooms on: Old wood
Flower type: White blooms age to pink or rose; striking oak-shaped leaves with fall color
Light: Full sun to part shade
Popular Selections: Alice, JetStream, Munchkin, Pee Wee, Ruby Slippers, Snowflake, Snow Queen, and the Gatsby series
Pruning: Oakleaf requires little maintenance and prefers to be left alone. Remove dead wood once new leaves emerge in late winter/early spring. Avoid cutting to the ground as they will not regenerate well.
Zones: 5-9 | Origin: Native to the southeastern US
Blooms on: Old wood
Flower type: White blooms age to pink or rose; striking oak-shaped leaves with fall color
Light: Full sun to part shade
Popular Selections: Alice, JetStream, Munchkin, Pee Wee, Ruby Slippers, Snowflake, Snow Queen, and the Gatsby series
Pruning: Oakleaf requires little maintenance and prefers to be left alone. Remove dead wood once new leaves emerge in late winter/early spring. Avoid cutting to the ground as they will not regenerate well.
Ruby Slippers Oakleaf Hydrangea | Image: Monrovia
Mountain Hydrangea (Hydrangea serrata)
Zones: 4-9 | Origin: Japan, Korea
Blooms on: Old and new wood
Flower type: Lacecap blooms in pink, blue, or lavender, depending on soil pH (blue or lavender in acidic, pink or red in alkaline)
Light: Full sun to part shade
Popular Selections: Tuff Stuff series (Tuff Stuff, Tiny Tuff Stuff, Tuff Stuff Top Fun, Tuff Stuff Ah-Ha) and the Let’s Dance series (Let’s Dance Can Do, Let’s Dance Sky View, Let’s Dance Blue Jangles)
Pruning: Pruning isn’t generally needed since they bloom on both old and new growth; however, you can remove old flowers and dead or weak stems in the spring.
Zones: 4-9 | Origin: Japan, Korea
Blooms on: Old and new wood
Flower type: Lacecap blooms in pink, blue, or lavender, depending on soil pH (blue or lavender in acidic, pink or red in alkaline)
Light: Full sun to part shade
Popular Selections: Tuff Stuff series (Tuff Stuff, Tiny Tuff Stuff, Tuff Stuff Top Fun, Tuff Stuff Ah-Ha) and the Let’s Dance series (Let’s Dance Can Do, Let’s Dance Sky View, Let’s Dance Blue Jangles)
Pruning: Pruning isn’t generally needed since they bloom on both old and new growth; however, you can remove old flowers and dead or weak stems in the spring.
Let's Dance Can Do! | Image: Proven Winners