Summer 2026
May: Heatwave #1, blazing sun
June: Heatwave #2, blazing sun, water restrictions
July: Heatwave #3, blazing sun, water restrictions and fires everywhere
What did we learn?
I can tell you is that it doesn't feel great to be a human in 42°C, five days in a row.
I can tell you that Riki, my German Shepherd only went outside to do his business and I've never seen him run so fast.
And from what I observed in my experimental gardens and my nursery, it wasn't great for the plants either.
But!
A few heatwaves is far from enough to snuff them out.
This week as the temperature settles back down to 'normal' (29-33°C), the new shoots and flowers are beginning to poke out of the mass of burned leaves or scorched buds.
The main conclusion that I have come to - with the help of quite a few books on heat stress and hydric stress in plants - is that drough tolerant perennials can withstand quite a bit of stress due to drought but high temperatures are quite a different story.
Wilting foliage, scorched foliage, burned buds, flowers fried in mid development, burned surface roots... this is something that will cause the aerial (above ground) parts of your plant to suffer and die back > this is what their survival strategy looks like. You can compare it to how we were bunkered down in our houses during the heatwaves, compulsively closing shutters, muttering angrily if a door or window was cracked open, lying flat as close to the floor as possible...
We bunkered, the plants bunkered.
Except their bunker is all the earth we cannot see. The beating sun dries out the top most layer of soil, killing microorganisms and nutrients (this is why mulching is so very important), but there is still life beneath that.
Their powers of resilience are derived from their ability to abandon ship when there is no point growing upwards when all that will meet them is a blazing and unforgiving sun, to drop flowers and leaves and try again at a better time.
Some might call it choice, some instinct, some reflex. What do you think?
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Here is Achillea 'Boule de Niege' :
Achilleas are notoriously indomitable but this variety has relentlessly grown back, even after the early flower buds of June were scorched by the second heatwave. Took nothing personal, took nothing to heart - the Snowball knows that the show must go on, so on she goes!
The same with Heuchera x villosa 'Black Pearl' - Heucheras are known for their shady/moist soil preferences but I've been interested in seeing how this cultivar resists drought in particular. I didn't have much hope as we entered the first/second/third heatwave but, as always, I was humbled. It seems that no one can predict the movements of the Black Pearl :)
Some of the plants in our nursery - raised mainly in 9x9cm pots, optimised in Roman Empire testudo infantry formation and protected by a 270° deep shade system - have now burst into bloom.
Testudo formation for reference : 
The same no?
The Mirabilis jalapa family have been stunning. Though their leaves wilted in the high heat, once the temperatures dropped, it's clear that their stamina has not been impacted in any way. This is due to the large tubers that form the root system (used historically in South America as a solution for erectile disfunction - confirmed by a recent NIH study from 2023, in case you were curious :) Tubers hold water and nutrients for the plant to tap into when the going gets rough - drought, heatwave, animal attack, etc..
Mirabilis jalapa 'Salmon Sunset'
Small, cute, rosy
Tall, impressive, fuchsia
And the winner of all winners - unflinching in the heat, thriving in the sun, blooming at the tail end of the third heat wave : Agastache 'Pink Pop'
With grey-green leaves that smell of lavender and sage, and tall inflorescences of a soft lilac-pink, she is perfectly entrancing. Hailing from Mexico, she is highly adapted to dry climates and scorching suns - provided that she has a winter to settle into her forever home. If you have her living in a pot, she will need to be watered (this should be common sense).
But then anything in an artificial environment will need to be cared for...
It's always better to set the wild ones free!
