Intro to Pruning Hydrangeas
Hydrangeas are deciduous plants native to Japan and East Asia. They are often planted in landscapes or containers for their lush foliage and large flowers that come in a variety of colors, including blues, pinks, reds and whites. To keep your Hydrangeas looking like statement pieces in your landscape, annual pruning is recommended.
Benefits of pruning:
To maintain the size of the plants
To promote strong, healthy growth
To enhance flowering
Tools You Will Need
Heavy duty garden gloves - Garden gloves will protect your hands from potential wounds from hardwood and cold temperatures.
Hand Pruners - These pruners are great for precision pruning smaller branches. (Make sure to disinfect with rubbing alcohol or warm soap and water before and between uses.)
Loppers - These larger pruners are for pruning thick canes that hand pruners are not strong enough to cut through. (Make sure to disinfect with rubbing alcohol or warm soap and water before and between uses.)
Types of Hydrangeas
Knowing the type of Hydrangea you have is important in knowing when to prune.
Some varieties produce flower buds in the fall on older wood that bloom in late spring to early summer. These include: Hydrangea petolaris ‘Climbing’, Hydrangea quercifolia ‘Oakleaf’ and Hydrangea macrophylla ‘Big Leaf’.
Other varieties produce flower buds in early spring on newer wood that bloom in early to late summer. These include: Hydrangea paniculata ‘Panicle’, Hydrangea arborescens ‘Smooth’ and Hydrangea macrophylla ‘Big Leaf’.
Hydrangea petolaris ‘Climbing’
Varieties: ‘Flying Saucer’,
Flower on older wood
Flower color: Cream-white to green-white
Produce Aerial roots for climbing
Hydrangea quercifolia ‘Oakleaf’
Varieties: ‘Jetstream’, ‘Gatsby’, ‘Snowflake’, ‘Alice’
Flower on older wood
Flower color: white to pink
Hydrangea paniculata ‘Panicle’
Varieties: ‘Barbara,’ ‘Bridal Veil,’ ‘Brussels Lace,’ ‘Chantilly Lace,’ ‘Grandiflora,’ and ‘Limelight.’
Flower on newer wood
Flower color: white to pink
Hydrangea arborescens ‘Smooth’
Varieties: ‘Annabelle’, ‘Grandiflora’, ‘Incrediball'
Flower on newer wood
Flower color: Cream-white to green-white
Hydrangea macrophylla ‘Big Leaf’
Varieties: ‘All Summer Beauty,’ ‘Altona,’ ‘Dooley,’ ‘Europa,’ and ‘Nikko Blue’, ‘Endless Summer’
Flowers on both older wood and newer wood
Flower color: Blues, pinks, purples, reds, white
Hydrangea macrophylla ‘Big Leaf’ flowers on both older and newer wood.
How to Prune Hydrangeas
Pruning Intensity
Thankfully, all pruning steps are the same regardless of the variety. Knowing how intensely to prune depends on the condition of the plant and the look you are trying to achieve. Below are a few terms to be familiar with when pruning:
Soft pruning
Removing flower heads as they die and general upkeep, including pruning off dead branches in late summer after flowering.
Hard pruning
Cutting back a majority of the plant up to ½ of the height and cutting entire branches to the base in spring after the last frost. (hard pruning in the fall or too early in the spring can cause damage to the freshly pruned stems).
Most hydrangeas can be soft pruned annually in late summer and don’t need to be hard pruned annually.
Hard pruning is mainly done to significantly reduce the size of the plant, to promote healthier growth or to revive a diseased plant.
When making any pruning cuts, try cutting right above a set of the healthiest looking buds. The healthier the buds, the healthier the new growth will be.
Pruning Old Wood Hydrangeas
Flower buds produced in the fall grow on stems referred to as ‘old wood’ or last season's growth. These varieties must be pruned right after the flower heads die in late summer so they have enough time to form new flower buds in the fall, before winter dormancy.
Hydrangea varieties that flower on old wood early in the summer are: Hydrangea petolaris ‘Climbing’, Hydrangea quercifolia ‘Oakleaf’ and Hydrangea macrophylla ‘Big Leaf’
Pruning too late in the year won’t allow the plants to produce buds before going into dormancy. Consequently, there won’t be flowers the following year in late spring - early summer.
Flower buds produced in the fall that will stay on the plant through winter dormancy must be protected from frosts so they can bloom the following spring. Cover your plants with white garden cloth when temperatures dip below 35° F to protect them. Remove the garden cloth when there is no sign of frost in the forecast for the remainder of the spring.
Pruning New Wood Hydrangeas
Flower buds produced in the spring grow on stems referred to as ‘new wood’ or current season growth. These varieties must be pruned in late winter to early spring after the last sign of frost for flower buds to form in late spring.
Hydrangea varieties that flower on new wood late in the summer are: Hydrangea paniculata ‘Panicle’ and Hydrangea macrophylla ‘Big Leaf’
Pruning Hydrangeas that flower on new wood too early in the season can cause cold damage to the exposed, bare stems. Pruning too late can remove flower buds and prolong flowering in late summer.
Pruning 'Big Leaf' Hydrangeas
One of the most common and popular types of Hydrangea is the Hydrangea macrophylla ‘Big Leaf’. This variety produces flower buds on both ‘older wood’ and ‘newer wood’ in the spring and fall. This means that ‘Big Leaf’ Hydrangeas are able to produce multiple flushes of flowers in a year.
In order to prevent pruning off viable flower buds on ‘Big Leaf’ Hydrangeas, lightly pruning off the flower heads after they die is the best practice. Any heavy pruning, such as cutting back branches should be done in the early spring as is done with ‘new wood’ Hydrangeas, to eliminate removing spring flower buds and to protect the plant from frost.
Hydrangea Pruning Steps
Step 1
Cut back any dead, diseased or unproductive branches to the base.
Step 2
Cut back weak, thin stems to the base, leaving 2-3 nodes for new growth to form.
Step 3
Open the center for air and light penetration by cutting some of the dense center branches to the base, leaving 2-3 nodes for new growth to form.
Step 4
Remove dead bloom heads by pruning down to a set of healthy looking buds.
Step 5
Shape the plant by cutting back stems to desired height up to ½ of the plant size, cutting right above a set of healthy looking buds.
Fertilizing Hydrangeas
Fertilizing hydrangeas regularly will strengthen their growth and allow them to produce quality flowers.
The large foliage and flowers on Hydrangeas cause them to be heavy nutrient feeders, so they should be fertilized monthly during their peak growing seasons of spring and
Summer (March - September).
Here are some fertilizers that work well with Hydrangeas
Soil Acidity & pH
Hydrangeas benefit from having their soils slightly acidic (pH 6.5 or lower). The acidity of the soil allows the plant to take up water soluble aluminum ions which help the plant absorb nutrients. These aluminum ions also allow Hydrangea flower pigments to change blue in color.
Hydrangeas grown in alkaline soils (7.0+ pH) will have pink or red flowers.
Aluminum is naturally present in soils, but can become depleted over time. Therefore, it is important to acidify soils by adding a layer of soil acidifier near the base of your Hydrangeas. The best time to amend with soil acidifier is late spring when plants are actively growing again after being dormant in winter.
Here are some soil acidifiers:
To wrap things up, first determine what type of Hydrangea you have and what time of year it produces flower buds. If you do not know the variety, it is best to watch when flower buds form before doing any hard pruning. When spring comes, fertilize and acidify the soil. To manipulate the flower color from blues to pinks or reds, adjust the soil pH.
If you have any more questions about how to care for your Hydrangeas, our specialists would love to assist you!