The moment we enter a heatwave, many experience what I've come to call 'temperature blindness' – the sudden and complete inability to imagine what a cold day feels like. The heat is so overwhelming that even though we'd love to frolic in the sunshine, days are often spent inside, shutters drawn, cold drink in hand.
At this time in the season, it does well to spare a thought for the plants in our gardens, which don't benefit from such luxuries. Firmly planted in beds and borders or intertwined with the poles of a pergola, they remain in their designated spot, rain or shine, relying on us to lend a helping hand.
Clematis is a popular garden flower that many would arguably rather keep alive than let succumb to the elements. Also known as the 'queen of climbers', clematis is a diverse genus of over 300 species that produce beautiful flowers of all colours, shapes and sizes sure to (literally) elevate any outdoor space.
There are generally three clematis groups, all with different flowering periods and caring requirements. The varieties most likely to bloom (and struggle) now are large-flowered Group 2 hybrids, like ‘Nelly Moser’, ‘The President’, ‘Mrs N. Thompson’, ‘Miss Bateman’ and ‘Hagley Hybrid’.
"These are the ones in full or near-full bloom right now, and their big petals don’t cope well in strong sun," plant scientist Dr Russel Sharp tells us. "In hot, bright conditions, the petals can fade quickly or get brown, crispy edges, especially on south- or west-facing walls where heat reflects back onto the plant."
Potted types are at an even greater risk as containers retain heat, causing them to dry out rapidly and, in turn, putting the plant under stress. "Poor drainage or compost that has gone compacted makes this worse because water doesn’t soak in evenly."
Even later-flowering Group 3 clematis, which cope better in heat, can struggle if they dry out fully or are attached to reflective surfaces that heat up quickly, so it's vital to keep a watchful eye on your favourite plant in the coming weeks.
How do I know my clematis is struggling in the heat?
Clematis isn't one to suffer in silence and will quickly show you if it needs help. "The flowers usually show the first signs," says Russell. "You might see petals fading faster than normal, looking bleached on the sunny side, or turning papery with brown edges. Leaves can also start to look dull instead of fresh and green, and edges may turn brown and crisp."
Dropping buds are another sign. "It often means the plant can’t keep up with water demand," the expert explains. "If you have a plant that droops in the middle of the day but looks fine again in the evening, it's usually coping, but if it doesn’t fully recover overnight, that’s a sign the stress is building."
For plants growing in pots, pay attention to receding compost. Soil that pulls away from the edge of the pots will cause water to simply run down the sides and drain away without ever reaching the roots of the plant.
What can I do to protect my clematis from heat stress?
The most obvious answer is often the right one, and it is also in this case: water, water, water. "The most important thing is deep watering at the base of the plant," says Russell. This is best done early in the mornings so the water actually reaches the roots before it evaporates in the midday heat.
The expert recommendation is to water the soil to around 15 to 20 cm deep and, for container plants, until the root ball is properly soaked. Good drainage is also important; don't let the pot sit in standing water during hot spells as this can suffocate the plant.
Another tip is to mulch, which helps your plant retain moisture throughout the day. "A 5 to 8 cm layer of bark or leaf mould helps stop moisture evaporating too quickly and keeps soil temperatures more stable. Just leave a small gap around the main stem so it doesn’t stay too wet at the base."
If the flowers are getting scorched, offer your plants some shade using a sheet, shade netting or even a parasol (sharing is caring, after all). Lastly, avoid feeding your clematis during the heatwave, as the extra boost can push new growth leaving the plant with an even greater need for water.
Water in the mornings and provide shade in the midday heat, and you can spend the rest of the day firmly planted in front of a cooling fan indoors – relaxed in the knowledge that your clematis will live to see another scorcher of a day.
Summer gardening edit
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Wanda Sachs is the Multiplatform Writer for Country Living and House Beautiful, exploring the latest in gardening, wildlife and sustainable living alongside interiors and property. She is particularly interested in human-interest stories, the intersection of design and pop culture, and the evolving relationship between urban and rural life. Previously, she served as Associate Editor at The Berliner in Berlin, where she reported on culture and fashion. Wanda studied English and German at the Goethe University Frankfurt and Exeter University.
