I love hydrangeas, so I have planted quite a few varieties in our garden over the past few years. Usually, at this time of the year, my garden is blooming with puffball flowers of different shades, but this year’s been a little different.
I’ve noticed my mophead hydrangea in my front border is struggling. Its once pristine white flowers have started developing brown patches, with some petals looking dry and crispy around the edges. I thought it might have been because it had simply finished flowering, but with so many of its blooms changing colour at once, I was suspicious there was something else going on.
After speaking to a few gardening experts, it turns out there are several reasons why my hydrangeas are turning brown, and thanks to this summer’s prolonged hot weather, they say more hydrangeas are turning brown than ever before. So, I don’t think I’m alone! Here’s their advice on why it’s happening and what to do about it.
1. Heat and strong sunshine
If your hydrangea has been flowering beautifully before suddenly developing brown, papery petals during a spell of hot weather, heat stress is probably to blame.
‘Whilst we are experiencing heatwave conditions, hydrangeas are likely to be turning brown due to them being scorched by the intense, direct sunlight,’ explains Lucie Bradley, gardening expert at Easy Garden Irrigation. She says hydrangea flowers are particularly delicate, especially mophead and lacecap varieties, with tissue-paper-thin petals that dry out quickly when exposed to prolonged sunshine.
It’s not just the flowers that suffer either. Lucie says leaves can wilt, curl and develop crispy brown edges when they’re exposed to too much direct sun or drying winds.
That certainly sounds like what has happened to mine. While the shrub itself still looks healthy, the blooms that catch the strongest afternoon sun are the ones browning first.
Jo McGarry, luxury garden design expert at Caragh Nurseries, agrees that placement makes a huge difference. ‘Hydrangeas tend to do best somewhere with morning sun and a bit of shade during the hottest part of the day. Too much intense afternoon sun can scorch the flowers and leaves, which can cause those brown patches.’
2. Hydrangeas are thirstier than you might think
The recent dry weather has also made caring for hydrangeas in a heatwave a priority, and more specifically, watering is far more important than usual.
Lucie explains that hydrangeas have relatively shallow roots, making them particularly vulnerable when the soil dries out. During prolonged hot spells, they lose moisture through their leaves faster than they can replace it, causing the plant to go into survival mode. While many hydrangeas recover overnight after wilting, repeated drought stress eventually leaves flowers and foliage brown and crispy.
Richard Barker, horticultural expert at LBS Horticulture, says a lack of water is one of the biggest reasons hydrangea flowers deteriorate in summer. ‘Hydrangeas are moisture-loving plants, and most varieties will need deep, frequent watering through summer to stop them from deteriorating. A lack of water can quickly turn flowers brown, as the plant needs consistent moisture to maintain its flowers.’
He adds that brown leaf tips often accompany browned flowers and recommends aiming for around an inch of water each week during the dry periods. While damaged blooms won’t recover, a watering routine can help protect any flowers that are still healthy.
The best thing you can do is to give them a deep watering, especially during dry periods, rather than sprinkling the surface. Adding a layer of mulch (we love RocketGro’s Magic Mulch, £14.99 at Amazon) around the base of the plant can help keep moisture in the soil for longer.’
Hydrangea care essentials
shirylzee
2pcs Root Watering Funnels
RocketGro
Organic Magic Mulch – 50l
Kimura
8″ Pro Bypass Garden Secateurs
Westland
Hydrangea High Performance Liquid Plant Food 1 Litre
Hardys
6L Green Rose Watering Can
3. Other causes worth checking
While heat and drought are by far the most likely explanation this year, experts say there are a few other possibilities.
Lucie warns that overfeeding can cause fertiliser burn, particularly if you’ve applied a feed that’s high in nitrogen. This often results in brown, crispy leaf edges alongside lush green growth but fewer flowers.
She also says fungal diseases such as leaf spot (which I think my plant has), botrytis blight and anthracnose can leave brown blotches on leaves and flowers. However, because these diseases thrive in warm, damp and humid conditions, they’re much less likely during dry weather. Plants that are already stressed by heat can still become vulnerable, though, particularly if they’re watered from overhead and the foliage remains wet.
Richard also recommends checking carefully for pests if watering and sunlight don’t seem to be the issue.
‘Hydrangeas can often be targeted by aphids and spider mites, which can cause damage to the flowers, leaves and stems,’ he says. Spider mites can be difficult to spot, so look for fine webbing and a dusty residue beneath leaves. Neem oil or insecticidal soap (this handy spray version is easy to use, £14.99 at Amazon) can help prevent infestations from spreading.
What I’m doing to help my hydrangea recover
Lucie recommends checking the soil moisture regularly before watering and directing water at the base of the plant rather than over the leaves. She also suggests applying a 5 – 8 cm layer of organic mulch, such as compost, leaf mould or Strulch (from £19.99 at Thompson & Morgan), to keep the soil cooler and reduce moisture loss.
Because my shrub sits in a particularly sunny spot during the afternoon, I’ll also be trying to give it some temporary shade whenever another heatwave arrives. Lucie says even positioning a patio parasol nearby or suspending an old sheet or shade netting above the plant between 10 am and 4 pm can help prevent further scorch. You could even pick up these cute little plant umbrellas, £11.54 at Amazon.
She also recommends removing the brown flowers completely using clean bypass secateurs (we really rate these Japanese Kimura secateurs, £24.99 at Amazon), cutting just above the first healthy pair of buds or leaves. Likewise, leaves that are more than halfway brown can be removed, but any with plenty of green should be left in place to continue producing energy for the plant.
If your hydrangea is growing in a container, simply moving it into a shadier position can make a noticeable difference. For shrubs planted in borders, though, Lucie advises waiting until autumn before relocating them, as moving a stressed hydrangea during summer can lead to transplant shock.
As disappointing as it is to see my once-white flowers turning brown, I feel reassured to know that it’s probably just a response to this summer’s hot weather. With plenty of deep watering, my favourite mulch and a little sun protection, I’m hoping my shrub will stay healthy and be ready to put on another cloud-like display next year.
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