There is always great confusion when it comes to pruning hydrangeas. Before you begin to prune your hydrangea you first need to know what type of hydrangea that you have.
Basically there are two pruning groups for hydrangeas:
– Method 1 –
Hydrangea macrophylla and Hydrangea quericifolia : mophead and lace-cap hydrangeas
Pruning Method 1 is for mophead and lace-cap hydrangeas or otherwise known as Hydrangea macrophylla. These hydrangeas typically have large, round, ball-like clusters of pink or blue flowers with just a couple of varieties being white blooming. Some cultivars of Hydrangea macrophylla have flat lacy flower clusters with the centre florets remaining sterile while the outer ring of florets being open. These are known as lace-caps hydrangeas. Some of the better known cultivars are: ‘Forever Pink’, ‘Nikko Blue’, ‘Bluebird’, ‘Marie’s Silver’, ‘Masja’, and the new Cityline series.
What you need to know about most mophead hydrangeas is that they bloom off of old wood. This means that next year’s flower bud is actually formed in late summer on this year’s current wood. If you were to prune back plants to the ground or if your plant suffered severe winter kill and died back to the ground, all new growth will emerge from the ground and will not produce any flower buds that season. So flower buds will only be produced on stems that were present from the previous year. So the key to promote flowering is to preserve as many branches above ground as possible.
The only reasons for pruning mophead hydrangeas are:
- To control the size of plant. This is done early spring by pruning back to just above a set of healthy, swelling buds. It is best to leave a minimum of 3 to 5 sets of buds from the ground up.
- To remove dead wood and damaged or crossing branches. After a more severe winter, you may notice that the existing stems have died back several inches. Simply cut back tip of stem down to the first pair of healthy buds. If a branch has no new buds in spring, cut back branch to the ground.
- To revitalize an older plant by removing about 1/3 of the older stems down to the ground each spring. This will promote new growth from the base of the plant, helping to keep the plant productive.
- To remove spent blooms. Old flower heads should be removed in fall or early spring. Do so by cutting below the old bloom to just above a set of healthy buds.
The one exception to this method of pruning in the newer ‘Endless Summer’ series of Hydrangea macrophylla including cultivars like: ‘The Original’, ‘Twist-n-Shout’ and ‘Blushing Bride’. This series of mophead hydrangeas have the unique characteristic of blooming on both the current season’s growth as well as old growth, providing the advantage of a longer bloom period. On average, they bloom for 10 to 12 weeks longer than other mophead varieties. The Endless Summer Hydrangeas can be treated like the other cultivars as described in Method 1 above, with very little pruning, or can be pruned back hard and still bloom. If you do prune it back hard or if it suffers severe die back, it will just be blooming off of new wood so it will begin blooming a bit later than normal and for not as long of period.
Also use Method 1 when pruning Oakleaf Hydrangea – Hydrangea querciflolia. This type of hydrangea has very large, oak-like leaves that turn maroon-red in fall and has large panicles of white flowers in summer that age to dusty-pink in fall.
– METHOD 2 –
Hydrangea arborescens (Annabelle) & Hydrangea paniculata (PeeGee)
Hydrangea arborescens (Annabelle Hydranageas) and Hydrangea paniculata (PeeGee Hydrangeas) fall into the same pruning method. Annabelle-type hydrangeas have large, snowball-like, white or pink flowers and include cultivars such as: ‘Annabelle’, ‘Incrediball’ and ‘Invincibelle. PeeGee Hydrangeas have large, cone-like panicles of white flowers that age to a dusty, rose-pink in colour. Some cultivars of PeeGee Hydrangea are: ‘Lime Light’, ‘Little Lime’, ‘Pink Diamond’, ‘Kyushu’, ‘Pinky Winky’, ‘Quick Fire’ and ‘Bobo’.
Booth of these families of hydrangeas bloom on new wood only. Therefore, they can take a heavy, early spring pruning.
Even though they can tolerate a heavy pruning, they do not necessarily require pruning every year. You can just give them a light cutting back in spring to clean up the previous year’s blooms and tidy up the plants. Remove any dead, damaged or crossing branches first. Then reduce size of plant to desired height.
Annabelle Hydrangeas can be pruned back to just several inches above the ground and still bloom that same season. It may help to prune Annabelle to about 18″-24″ tall rather than cutting it to the ground every year. This will allow the stems to thicken a little each year, becoming stouter and better able to support the other branches and blooms. In addition, the heads will be more plentiful but slightly smaller (not so small that you will be disappointed). The slightly smaller heads will be less likely to droop.
For Hydrangea Availability & Questions visit us at
Mori Gardens, 1709 Niagara Stone Rd., NOTL, ON
or contact our Garden Experts at info@MoriGardens.com & (905)468-7863