What to do with hydrangeas in August – these are the non-negotiables to keep them looking their best in high summer into Autumn
Look after your hydrangeas through the summer to keep them happy, healthy and returning year after year, say the experts
For most of us, this summer has been all about ‘hot weather’ gardening, and trying desperately to keep our plants and flowers alive and watered in the heatwave. My thirsty hydrangeas are suffering most – and as they are one of my favourites (in fact one of the first things I ever planted) – I’m keen to get some expert advice on what to do with hydrangeas in August so that I can keep them thriving.
‘When summer temperatures climb into the 20s and 30s, certain garden plants need extra help handling the heat,’ says Shelley Davis, flower expert at Flying Flowers. ‘Hydrangeas (which literally translates to ‘water vessel’) are particularly thirsty, so require extra care when it comes to what to do with hydrangeas in a heatwave.’
‘In August, your focus is all about making sure your hydrangeas will look their best for the rest of the summer,’ agrees David Denyer, flower and garden expert at Eflorist. ‘They are in full bloom at this time of year, so watering and feeding are priorities over heavy pruning.’
1. Deep water in hot weather
‘Living up to their ‘water vessel’ name, hydrangeas need consistent moisture to survive the summer heat,’ says Shelley. ‘During July and the hotter months, focus on deep watering at the base of the plant once or twice a week rather than light, daily surface sprays. A good tip is to test the top two inches of soil and, if it feels dry, then it’s time to water them.’
‘A top tip is to reuse an old plastic bottle with the bottom cut off, and carefully place it in a hole upside down next to your hydrangea plant as far as you can so the top is slightly above the soil line. After watering normally, fill the bottle up, as this will gradually seep out deeper and closer to the main roots. This is ideal when there’s a hosepipe ban or heatwave to keep the plant constantly hydrated,’ adds Shelley.
‘If you’re enjoying cut stems and notice the flowers starting to wilt, try dunking the entire flower head upside down in a bowl or sink of cool water for around 20 minutes,’ advises Shelley. ‘Hydrangeas can actually absorb water directly through their petals, making this quick bath the ultimate trick to plump drooping blooms right back to life.’
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2. Avoid watering in the heat of the day
‘When it comes to watering in hot weather, timing is all important,’ says Chris Bonnet, founder of Gardening Express. ‘Hydrangeas need deep watering at the base of the plant early in the morning to soak the roots. The large leaves lose moisture quickly during summer heatwaves and if the plant uses up its water supply, the blooms will droop and foliage will scorch and turn brown.’
David Denyer agrees: Watering first thing in the morning or the last thing at night is advisable. That way you’ll ensure that as much moisture as possible reaches the roots instead of evaporating in the sun. Hydrangeas are naturally thirsty and can begin to wilt during long periods of hot and dry weather, so a deep soak once or twice a week, rather than little and often, is best.
3. Mulch to lock-in moisture
‘During hot weather, applying a layer of organic mulch around the base of your hydrangeas can make a real difference,’ says David. ‘Garden compost or well-rotted bark helps lock in moisture to the surrounding soil, reduces evaporation, and keeps roots cooler.’
‘Topping up mulch around your hydrangeas will help the plant retain soil moisture and survive the hot weather,’ says Chris. ‘The mulch helps with moisture retention, keeps the soil cooler and helps prevent weeds from germinating.’
‘While there are different types of mulch, opting for an organic mulch, such as RocketGro Organic Magic Mulch, £14.59, Amazon, or bark chips, around the base of the shrub to help the soil retain essential water through the heat,’ advises Shelley. ‘Just be sure to leave a small gap around the main stems to prevent rotting and allow fresh water to reach the roots easily.’
‘Hydrangeas are also acid-loving plants, so sprinkle used coffee grounds around the base of the plant, give the soil a turnover and mix in the grounds,’ adds Shelley. ‘Your hydrangea will thank you for a little extra nutrient boost.’
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4. Shield hydrangeas from the sun
‘During intense heatwaves, hydrangeas planted in full sun may need a temporary shield against the elements as direct, scorching rays can quickly burn leaves and ruin delicate blooms,’ advises Shelley.
‘Setting up a patio umbrella or plant parasol, like this adjustable plant umbrella, £7.89 from Amazon, or draping a light cotton sheet or horticultural fleece over the shrub during peak afternoon heat works wonders at shading plants. Just make sure the shade cover hovers a couple of feet above the plant. If it sits directly on top, heat gets trapped underneath, creating an accidental sauna that can damage the leaves.’
‘And if you are growing hydrangeas in a pot, consider relocating to a shaded area during intense, hot periods,’ adds Shelley.
5. Tidy up plants but don’t hard prune
‘It’s a common hydrangea pruning mistake, but it’s important not to cut your hydrangeas back too early, says David. ‘Hard pruning hydrangeas during August might impact flower buds that have begun growing on old wood, and you don’t want to sacrifice next summer's blooms by being too hasty now.’
‘If the flowers on your plants start to fade, try deadheading individual blooms instead of removing every flower. Ageing hydrangea heads produce eye-catching pink and green tones during autumn months, so you may want to keep them,’ adds David.
Deadhead the blooms on old-wood hydrangeas like mopheads, lacecaps and oakleaf varieties
‘Late July and August can be the prime time to give your hydrangeas a light haircut,’ advises Shelley. ‘But do make sure you check which variety you have first.’
‘Old-wood hydrangeas like mopheads, lacecaps, and oakleaf can have a tidy up before the end of the month, but new-wood varieties like paniculata and Annabelle should be left to prune in late winter or early spring.’
‘Just be careful not to go overboard,’ adds Shelley. ‘Heavy pruning hydrangeas in midsummer can rob you of next year’s flowers, which defeats the purpose. It’s all about a light touch and, if you’re in doubt, stick to removing faded or damaged flower heads and tidying up stray branches.’
Prune climbing hydrangeas after flowering has finished in late July or August
‘Leaving faded blooms on mophead hydrangeas will help protect new buds from damage,’ adds Chris. ‘But when it comes to pruning climbing hydrangeas, prune these after flowering has finished (typically late July or August), which gives the plant time to develop fresh wood and new flower buds for the following year. It will also keep the plant looking neat and tidy for the remainder of the summer.’
How are your hydrangeas faring this summer? Let us know how you have been looking after them in the hot weather.
