Summer has landed. Temperatures are soaring and our gardens are baking in the sun. While a few days in the sun feels glorious to us, our gardens, usually calm and full of life, can quickly lose their cool.
Many of our favourite flowers struggle when the heat becomes relentless. The signs are usually easy to spot once you know what to look for: leaves drooping, fading colours and petals or leaf edges turning dry and crisp.
Below, we’ve rounded up six flowers that need extra attention during hot spells – and how to give them a little heatwave first aid.
1. Roses
Roses are a cottage garden favourite but prolonged heat can quickly take its toll on their blooms.
"Deep pinks, reds and purples absorb more heat from the sun, so petals can scorch surprisingly quickly," says Elise Harlock, expert at Prestige Flowers. "That's often why flowers start looking papery even when the soil is still damp."
High temperatures can also affect flowering. "While many roses are robust, they prioritise survival, slowing growth and the production of new blooms when temperatures soar," Elise explains. "This stress response can disrupt and shorten their flowering display."
The RHS advises giving roses extra water during hot, dry spells, particularly if they are growing in light, sandy soils that drain quickly.
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2. Hydrangeas
Hydrangeas bring generous colour in late summer, but they aren’t plants you can leave to fend for themselves in a heatwave.
"Hydrangeas are thirsty plants," says Melissa Quinney, gardening expert at Cabin Master. "During a heatwave, their large, soft leaves and bountiful flower heads lose water at an alarming rate, causing them to wilt dramatically and become irreversibly damaged if left unwatered."
Newly planted hydrangeas need the most care. The RHS recommends watering them in their first growing season if there hasn't been much rain for seven to ten days. Mature hydrangeas may also need extra watering in the heat.
If you can, mulch before the hot weather arrives. The RHS suggests using organic matter, such as “leaf mould, garden compost or a manure-based soil conditioner”, to help the soil hold on to moisture for longer.
3. Astilbes
"Astilbes are moisture-loving perennials that thrive in damp, cool conditions, making them one of the first plants to suffer when the weather turns hot and dry," says Melissa. The RHS adds that astilbes dislike dry conditions, even in summer, so prolonged heat can quickly leave them stressed.
Melissa says gardeners should watch for wilting foliage and brown, crispy leaf edges, both signs that the plant is struggling to retain moisture. She recommends watering deeply at the base and applying mulch to help keep the soil cool and damp.
4. Fuchsias
Fuchsias are often grown in containers, hanging baskets and patio pots, where they can dry out quickly in hot weather. The RHS says these plants need more frequent watering than those in the ground, while Elise warns that dark pots can become very hot in direct sun. "Sometimes the roots are overheating even when the plant above looks relatively healthy," she says.
Elise stresses that timing matters during a heatwave. Watering in the morning gives roots time to absorb moisture before temperatures peak, while allowing leaves and petals to dry during the day.
She also recommends watering slowly rather than giving plants a sudden soaking. "Fast watering encourages shallow roots, so watering slowly can help flowers become more resilient because their roots travel further down into cooler soil."
5. Phlox
"Phlox produces a significant amount of fleshy, lush growth in mid-summer, which demands a high volume of water to sustain it," says Melissa. "In a heatwave, their shallow root systems can struggle to draw enough moisture from drying soil, causing yellowing leaves and faded blooms."
During extreme heat, Elise says fading flowers can put extra strain on the plant. "As soon as flowers begin to fade, the plant starts putting energy into seed production," she explains. "In hot weather, that extra effort can drain the plant very quickly."
Deadheading spent blooms can help reduce that strain and encourage the plant to focus its energy on healthy growth.
6. Dahlias
Dahlias are prized for their large, colourful blooms, but all that flower production means they need plenty of water to perform at their best. Extreme heat can leave them struggling to flower well. The RHS says those growing in the ground need additional watering during dry, hot spells.
Elise also recommends giving dahlias temporary protection during the hottest part of the afternoon if they are visibly struggling. "Delicate plants such as dahlias can deteriorate quickly during intense heat," she says. Moving taller neighbouring plants or even putting up an umbrella for a few hours can help reduce stress without affecting flowering.
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