Blue hydrangeas are one of the most sought-after flowering shrubs due to their stunning large blossoms in shades of sky blue. But getting those coveted blue blooms requires specific care when it comes to choosing the right variety, providing acidic soil, watering, feeding, pruning, and winter protection. Follow this complete guide to properly grow, feed, water, and prune blue hydrangeas for optimal flower production and plant health.
Choosing Blue Hydrangea Varieties
While all hydrangeas are beautiful, only certain types can produce blue flowers. Focus on these varieties:
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Bigleaf hydrangea (Hydrangea macrophylla) – The classic hydrangea for blue blooms. Popular cultivars are Nikko Blue, Endless Summer, and Blauer Prinz.
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Mountain hydrangea (Hydrangea serrata) – A smaller type that blooms on new wood, so pruning is easier. Good choices are Blue Billow and Munchkin.
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Climbing hydrangea (Hydrangea anomala subsp petiolaris) – Stunning vine with blue lacecap blooms, Can reach 60 feet
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Smooth hydrangea (Hydrangea arborescens) – ‘Dardom’ BLUE BALL is an exception that can produce blue flowers on this species
When shopping, check the photos on the tag to confirm the variety produces blue blooms. Avoid varieties known for pink or white flowers.
Providing Acidic Soil
The key to blue flowers is acidic soil with a pH between 5.0-5.5. Most garden soils are neutral to alkaline, so amendments are needed to lower pH for blue hydrangeas.
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Test soil pH yearly using a home kit to monitor changes.
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To increase acidity, mix in elemental sulfur, aluminum sulfate, or a formulated hydrangea acidifier.
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Re-test soil after a few weeks and re-apply acidifier as needed until optimal pH is reached.
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Maintain proper pH by applying acidifier around plants each spring and fall.
Proper Planting
Give new hydrangea plants the best start:
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Choose a site with full sun in the morning and afternoon shade. This prevents blossoms from wilting.
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Improve drainage if needed. Hydrangeas dislike soggy soil.
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Dig a hole twice as wide as the root ball but no deeper.
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Set the plant at the same level it was growing in the pot. Don’t bury the base too deeply.
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Backfill with amended native soil. Don’t use straight compost.
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Water thoroughly after planting and as needed the first year.
Watering Blue Hydrangeas
Established plants need 1-2 inches of water per week from rain or irrigation.
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Daily watering is needed for the first season as roots establish.
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Water at soil level rather than from overhead to avoid fungal issues on leaves and flowers.
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Drooping leaves are a sign plants need more water.
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Add mulch around plants to retain soil moisture. Avoid letting mulch touch the stems.
Feeding Requirements
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Fertilize in early spring before new growth emerges and again in midsummer.
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Use an acid-based fertilizer formulated for acid-loving plants such as hollies and azaleas. This maintains optimal soil acidity.
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Alternate between rapid release and slow release fertilizer for continuous feeding.
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Follow package rates since different products have varying strengths.
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Discontinue feeding after August to harden off new growth before winter.
Pruning Tips for Healthy Plants
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Remove spent flowerheads in summer by cutting back to the first set of healthy leaves to encourage reblooming.
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In late fall, cut each stem down to two healthy nodes above soil level.
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In spring, prune only dead, diseased or damaged stems. Never prune live wood that has visible flower buds.
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For climbing hydrangeas, simply cut out dead growth. Otherwise, refrain from heavy pruning.
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Limit pruning on varieties that bloom on old wood to immediately after flowering.
Protecting Hydrangeas in Winter
In cold climates, protect plants from winter damage:
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Wrap or cover plants to protect from desiccating winds. Avoid excessive mulching which can cause rotting.
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Paint stems with white latex paint to prevent sunscald.
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Surround plants with burlap wind barriers. Place stakes around plants and drape burlap inside the stakes.
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Move potted plants to an unheated garage or basement once they drop leaves. Water sparingly during dormancy.
With the right care to support blue blooms, hydrangeas will thrive for years of stunning color. Test soil regularly, provide adequate water and fertilizer, practice careful pruning, and protect from winter damage for the healthiest plants with abundant blue blossoms. Follow these tips and you’ll be rewarded with a spectacular display of sky blue hydrangea flowers.
How can I ensure the blue color of my hydrangeas is vibrant?
To get a vibrant blue color, keep your soil consistently acidic, make sure your hydrangeas can access enough aluminum, and take good care of them with appropriate watering, sunlight, and nutrients.
Can all hydrangeas change color or just certain types?
Not all hydrangeas change color. Its primarily bigleaf (Hydrangea macrophylla) and mountain hydrangeas (Hydrangea serrata) that can shift from pink to blue based on soil pH.
Step by step: How to turn Hydrangea Flowers Blue
FAQ
How to keep your blue hydrangeas blue?
Adjust Your Soil’s pH
To turn hydrangeas blue, you’ll need to make your soil more acidic. You may have heard of tricks like adding coffee grounds, vinegar or even pennies or a bundle of rusty nails to the soil. However, it’s best to use aluminum sulfate, which is a proven method for changing flower color.
Do you cut back blue hydrangeas?
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When to Prune:Prune bigleaf hydrangeas after they finish blooming, usually in late summer, before the plant goes dormant.
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Why Prune:Pruning helps maintain the plant’s shape, size, and encourages healthy growth and blooms.
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How to Prune:
- Remove dead, diseased, or broken branches.
- Cut back stems to a set of healthy buds.
- For heavier pruning, remove older or gray stems during winter, or prune back about one-third of the older stems almost to the ground if the plant is overgrown.
- Remove dead, diseased, or broken branches.
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Pruning “Old Wood” vs. “New Wood”:Bigleaf hydrangeas bloom on “old wood” (growth from the previous year), so pruning in early spring can remove the flower buds for the following year.
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Ever-blooming Hydrangeas:Some ever-blooming hydrangeas, like Endless Summer, bloom on both old and new wood, so they should be treated similarly, pruned in late summer after the blooms have faded.
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Panicle Hydrangeas:Panicle hydrangeas bloom on new wood, so they can be pruned in late winter or early spring before new growth begins.
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Other Hydrangea Types:Not all hydrangeas require the same pruning techniques. Some varieties, like panicle hydrangeas, may not require as much pruning as bigleaf hydrangeas.
Do coffee grounds keep hydrangeas blue?
Some gardeners report success in turning their hydrangeas blue by applying coffee grounds to the soil. However, it’s best to use aluminum sulfate, a proven method for changing flower color.
Should I deadhead blue hydrangea?
You do not need to dead head a hydrangea. That material will eventually decompose in the spring/summer, but you should dead head if you want to avoid build up of that bacteria.
How to care for Blue hydrangeas?
Importance of Well-Draining Soil: Ensuring that the soil is well-draining is crucial for the health of blue hydrangeas. Poor drainage can lead to root rot and other issues. Amending heavy soils with compost or other organic matter can improve drainage and soil structure.
How do you care for hydrangeas?
Be sure to clean the flowers really well—I like to take off all the leaves and make them look almost stark. Then put them in a beautiful vase and let them go all over the place like an octopus or a jellyfish—you end up with a beautiful, contained sort of wildness. If you’re looking for volume, a big cloud of hydrangeas is the way to go.
How much water do hydrangeas need?
Provide hydrangeas with about one to two inches of water per week to increase blooming. Installing a drip irrigation system can automate watering for even easier care. Apply a two to three inch layer of natural mulch around hydrangea plants once a year to shelter plant roots and keep soil from drying out too quickly.