How to Care for Blue Hydrangeas: A Complete Guide

With their large, showy blossoms in shades of sky blue, blue hydrangeas are highly desirable additions to any garden. But getting those coveted blue blooms requires specific care. 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:

Bigleaf hydrangea (Hydrangea macrophylla) – The classic hydrangea for blue blooms. Popular cultivars are Nikko Blue Endless Summer and Blauer Prinz.
Mountain hydrangea (Hydrangea serrata) – A smaller type that blooms on new wood, so pruning is easier. Good choices are Blue Billow and Munchkin.

Climbing hydrangea (Hydrangea anomala subsp. petiolaris) – Stunning vine with blue lacecap blooms. Can reach 60 feet.
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.

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.

Test soil pH yearly using a home kit.
To increase acidity, mix in elemental sulfur, aluminum sulfate, or a formulated hydrangea acidifier.
Re-test soil after a few weeks and re-apply acidifier as needed until optimal pH is reached.

Maintain proper pH by applying acidifier around plants each spring and fall.

Proper Planting

Give new hydrangea plants the best start:

Choose a site with full sun in the morning and afternoon shade. This prevents blossoms from wilting.
Improve drainage if needed. Hydrangeas dislike soggy soil.
Dig a hole twice as wide as the root ball but no deeper.

Set the plant at the same level it was growing in the pot. Don’t bury the base too deeply.
Backfill with amended native soil. Don’t use straight compost.
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.
Daily watering is needed for the first season as roots establish.
Water at soil level rather than from overhead to avoid fungal issues on leaves and flowers.

Drooping leaves are a sign plants need more water.
Add mulch around plants to retain soil moisture. Avoid letting mulch touch the stems.

Feeding Requirements

Fertilize in early spring before new growth emerges and again in midsummer.

Use an acid-based fertilizer formulated for acid-loving plants such as hollies and azaleas. This maintains optimal soil acidity.
Alternate between rapid release and slow release fertilizer for continuous feeding.
Follow package rates since different products have varying strengths.

Discontinue feeding after August to harden off new growth before winter.

Pruning Tips for Healthy Plants

Remove spent flowerheads in summer by cutting back to the first set of healthy leaves to encourage reblooming.
In late fall, cut each stem down to two healthy nodes above soil level.

In spring, prune only dead, diseased or damaged stems. Never prune live wood that has visible flower buds.
For climbing hydrangeas, simply cut out dead growth. Otherwise, refrain from heavy pruning.
Limit pruning on varieties that bloom on old wood to immediately after flowering.

Protecting Hydrangeas in Winter

In cold climates, wrap or cover plants to protect from desiccating winds. Avoid excessive mulching which can cause rotting.
Painting stems with white latex paint prevents sunscald.
Surround plants with burlap wind barriers. Place stakes around plants and drape burlap inside the stakes.

Move potted plants to an unheated garage or basement for winter 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, and practice careful pruning for the healthiest plants with the most abundant blue blossoms.

It’s all about soil chemistry By

As a founding employee of Gardeners Supply, I wore many different hats over the years. Currently, I have my own company called Johnnie Brook Creative. The gardens around my home in Richmond, VT, include a large vegetable garden, seasonal greenhouse, cutting garden, perennial gardens, rock garden, shade garden, berry plantings, lots of container plants and a meadow garden. Theres no place Id rather be than in the garden. If youd like to learn more, check out this January 2021 video interview by Garden Gate magazine.

You may have heard that you can change the color of a hydrangeas flowers by adjusting soil pH. But theres a little more to it than that.

First of all, not all hydrangeas produce blue flowers. Hydrangeas with white or cream flowers, like Annabelle hydrangeas, oakleaf hydrangeas, and PeeGee family members, can only make flowers that are white or cream. Their blooms sometimes turn pink near the end of the season, but that’s about all the color they get.

Hydrangeas with bloom colors that range from pink through blue and purple usually belong to the hydrangea cultivars known as mopheads and lacecaps. These types of hydrangeas have the interesting ability to change the color of their blooms based on the chemistry of the soil. When grown in alkaline soil, the bloom colors are pinker. When grown in acidic soil, the bloom colors are bluer. Watch below, as Laura from Garden Answer highlights 16 gorgeous hardy hydrangeas!

What Makes Hydrangeas Pink?

If you want your hydrangea to bloom pink, you should grow it in alkaline soil with a pH of 6 to keep it from getting aluminum. 0-6. 2. You can apply a high-phosphorus fertilizer to further discourage the uptake of aluminum. To make naturally acidic soil less acidic, use Garden Lime at the rate written on the package.

Step by step: How to turn Hydrangea Flowers Blue

How do you care for a blue hydrangea?

Soil: Fertile, well-draining soil rich in organic matter. Soil pH: Acidic soil (below 6.5 pH) is necessary for blue blooms. Water: Keep soil consistently moist. Hydrangeas need regular, deep watering but avoid waterlogging. Mulch: Use organic mulches to retain soil moisture, and regulate temperature.

How do you grow a blue hydrangea?

Pick the Flower Hue You Want For true blue flowers, the hydrangeas need to be grown in acidic soil with a pH of 5.5 or lower. For pink flowers, the plants need neutral to alkaline soils (pH 6.5 and higher). For purple blooms (or a mix of blue and pink flowers on the same plant), the pH of the soil must be between pH 5.5 and 6.5.

How do I know if my soil is good for Blue hydrangeas?

Understanding your soil’s pH is essential when aiming to grow blue hydrangeas. Follow these simple steps to find out the pH level of your soil: Buy a soil test kit: You can purchase these kits at gardening stores or online. They don’t cost much and are easy to use.

Why do hydrangeas have blue flowers?

There is an easy answer to this, and it all lies in the pH of your soil. For your hydrangea to have blue flowers the soil needs to be acidic. Pink flowers are a sure sign of alkaline soil. Now you can either leave nature to do its own bidding, or you can treat your soil with aluminum sulfate.