Why has my Blue Hydrangea turned Pink?

Why has my blue Hydrangea turned pink? Or conversely – why has my pink Hydrangea turned blue?

Hydrangeas are a popular flowering garden shrub; but one that frequently confuses us by changing flower colour a little while after its been planted. And it can possibly be a couple of years before you realise the change has occurred, as the colour change is likely to be a gradual process.

The question that then becomes one of the first questions a new student or garden design client asks, is – can the colour be changed back? Is the Hydrangea dying? is an other concern.

Will my Hydrangea die if it changes colour?

It is unlikely that your Hydrangea is dying if the only issue is the colour change from blue to pink or pink and purple to blue flowers. Generally speaking Hydrangeas are easy shrubs to look after. However, as we shall see below, your Hydrangea changing colour may have underlying causes that may later on affect the general health of the shrub.

Why has my Blue Hydrangea turned Pink?

Not all types of Hydrangea will change their flower colour after you get them home and planted in the garden. whether they do is dependent on the soil.

Hydrangea macrophylla, also known as mop-head hydrangeas, are the shrubs most often found in gardens. They’re called mop heads due to their round balls of flowers. By contrast, lace cap hydrangeas small fertile flowers surrounded by larger sterile sepals.

These two varieties of hydrangeas will very probably change colour according to your soil pH. Theis is how acidic or alkaline your garden soil is, and is easy to check with a pH meter or test kit from a garden centre. See also the blog links below.

The reason is not purely down to the acidity of the soil, but the effect this has on the levels of aluminium in the soil. The more acidic the soil, the higher the aluminium levels and this will turn pink and purple hydrangeas blue. A soil pH of 6 or below should keep the blue flowered.

Therefore the trick is to check the soil pH before you buy a mop-head or lace cap Hydrangea if you want to be sure of keeping the flower colour.

How do I Keep my Blue Hydrangea Blue?

You can encourage this by mulching your Hydrangeas with leaf compost.
Alternatively, plant your mop head Hydrangeas in an ericaceous bed filled with a peat free ericaceous compost. You could plant your Hydrangeas along with Rhododendrons and Azaleas. Putting all the acid loving plants together will not only keep them happy, but you’ll get a flowering display from April to October.

How do I Keep my Pink Hydrangea Pink?

By having an alkaline soil, ie one which is pH 7 or above. A pH between 6.5 – 7 should be ok, mulch with spent mushroom compost to help to maintain the alkalinity.
However if your soil is acid, why not grow your Hydrangeas in pots? They could look very effective, one on either side of your front door.

What about my Purple flowered Hydrangea?

Good question! The answer isn’t one I can easily answer, as it depends not only on the soil, but also on the parentage of the shrub. Which is why although most purple Hydrangea flowers will turn pink in an acid soil, some don’t.

Why has my Blue Hydrangea turned Pink – More Solutions to the Problem

Why not make your life easier in the first place, and choose a Hydrangea that won’t change colour when you plant it? Not all Hydrangeas have the same flower colour changing tendencies.
For example, white and green flowering varieties tend not to change colour; even in the macrophylla cultivars.

Or choose a different type of Hydrangea!

Hydrangea petiolaris

Also known as the climbing Hydrangea. It is a vigorous, self-clinging climbing shrub, grown for its white flower heads.
It takes time to become established but can then become vigorous and may need pruning if it’s not to climb into your gutters!
The dark green foliage turns butter yellow in autumn before leaving a tracery of branches over the winter. The young twigs are an attractive, shiny reddish brown.

Hydrangea paniculata

These Hydrangeas have cone shaped florets – panicles – up to 8 inches long. Most cultivars flower in late summer and autumn.

Hydrangea quercifolia

Huge leaves shaped like oak leaves have red autumn tints. The flowers are white and the foliage is evergreen, unlike most other Hydrangeas.

Hydrangea – Pruning Tips

Of course, its not just about why your blue Hydrangea turned pink. You may be wondering why there are no flowers at all, even though you pruned the shrub…
Although they do not require much pruning, having a plan that encourages new wood will prevent your hydrangeas from becoming too woody. Read on to check you got the pruning right for your type of shrub.
Many summer-flowering deciduous shrubs can be pruned between February and early March; usually those that flower on the current year’s growth. Hydrangea paniculata is one of those that require regular pruning.
Mop-head hydrangeas flower on the previous year’s wood. Deadheading by taking back to a strong pair of shoots can be done in late February if you’re in a mild area, or you can leave until March.

What next?

Now we know why that blue Hydrangea turned pink and which colour flowers stay the same as when you bought the plant.
You may like to find and follow us on your preferred social media – Instagram Facebook Pinterest for more inspiration and gardening advice.

If you would like a real life, on-site or a virtual design visit to include lots of lovely Hydrangeas in your garden, do get in touch – Plews is able to offer you Garden Design and Planting Designs.
Or perhaps you would prefer gardening lessons in your own garden? Because where better to learn about what’s relevant to you as a gardener? Plews Gardening Courses and Lessons are bespoke to you and your garden and combine hands on confidence giving with necessary ‘why we do this’ reasons.

Gardens to visit with Hydrangeas

If you’d like to enjoy hydrangeas en masse, Holehird gardens, home to the Lakeland Horticultural Society has a Hydrangea walk with over 300 species. If you’re not convinced about the beauty of Hydrangeas, this is the place to visit in July and August as you’re sure to find a Hydrangea for your own garden. See an account of one of my visits in the blog list below.
Other parts of the UK with acidic soil often have good displays of Hydrangeas, even if they don’t have the variety of species as offered at Holehird. For example, the shady drive at Portmeirion has glowing Hydrangea shrubs outlining your route; very atmospheric. other gardens in Cornwall, the west coast of Scotland and Ireland are worth checking out.

For further gardening advice and inspiration, check out Plews Potting Shed blogs, including the selection below and our monthly Tipsheet – You could come and find us on Instagram Pinterest and Facebook too.