It hit me like a smack in the face. This year’s RHS Chelsea flower show was quite blatant in showcasing the effects of climate change; you may not have noticed though. Most people visiting the show or tuning into the BBC coverage were homed in on the increasingly more naturalistic planting style, the reduced number of large show gardens and the amazing lupins.

However, the increasing temperatures that our planet is experiencing are catching up with us gardeners. While the changes may be subtle in our own gardens, when you see them distilled and condensed, as I did at the world’s greatest flower show, the dawning realisation that they are real comes as quite a shock.

The first thing I noticed on entering the show was just how hot it was. It was a pleasure to walk around the show gardens on such a lovely sunny day, but in the back of my mind I had the realisation that the heat was part of an extended period of drought that the southeast, and the UK more generally, had been suffering. On talking to the gardeners and designers I heard many an exclamation of “I can’t wait for it to rain”. After such a very warm, wet winter in 2016 and then this, the driest winter for 20 years, I wondered if these unpredictable weather events are what we should come to expect in future?

‘I wanted to clamber into it and botanise between the columns of limestone’: James Basson’s Chelsea garden for M&G. Photograph: Jim Powell/The Guardian

Almost the first show garden I clapped eyes on rammed the point home a little further. James Basson’s M&G garden was an absolute triumph in my eyes. It transported me directly to the lime stone quarries of the Mediterranean and fitted so beautifully with the sun’s heat. I wanted to clamber into it and botanise between the columns of limestone. I could see plants of one of my favourites from the region, white henbane (Hyoscyamus albus), winking at me with its black eye from among the rocks and prickly goldenfleece (Urospermum picroides) shining at me, reflecting the yellow sun above.

While revelling in such delicate and beautiful planting, I couldn’t help but feel that this was what the southeast of the UK may have to count as normal in future years. We may have to accept some of these Mediterranean species as the newcomers in place of the hedgerow plants and garden weeds that we feel so comfortable with.

The next port of call was with my friend Charlotte Harris on her Royal Bank of Canada garden; an exquisite recreation of the boreal forests of Canada. With little leeway on the accuracy of the species used in the garden there were, again, plants here that piqued my interest. Sweet fern (Comptonia peregrina) jumped out at me from the corner of the plot, and labrador tea (Ledum groenlandicum) had a presence only felt once you knew it was there.

These two gardens felt like the antithesis of one another, yet the plants within them are so bound to this changing climate that they shared something deeper. The boreal forests of Canada, you see, are expected to warm at above the global average, and the species within them will be unable to keep up. The coniferous trees are burning more frequently than their ecology can handle and, if not burning, then being pushed north by drought stress and competition from the more rugged deciduous species that will take their place. Who knows how long comptonia has left on the planet it has called home for more than 60 million years?

These two gardens took my mind to the effects on the earth’s natural landscape but the next, Manoj Malde’s Inland Homes garden, Beneath a Mexican Sky, made me think of the impact a changing climate is having on the UK’s gardens. When asked if I thought that plants such as agaves and aloes would be hardy in a British garden, my answer, after a momentary pause, was an emphatic “yes”.

Coming to a British garden near you ... an agave plant. Photograph: Alamy Stock Photo

I had seen plants of Dracaena draco, the dragon tree, growing outside just the day before at the Chelsea Physic Garden, and just a month earlier I had visited a garden in Kent where the traditional rockery plants were being ousted by agaves and other succulents, alongside Mediterranean climate species from all around the world. For the first time, maybe also because of the sun, the vibrant colours of Malde’s garden looked right beneath a very British sky.

A colour I fear may be heading for a fall in the gardens of our little island is the clear blue of Himalayan poppies (Meconopsis). Chris Beardshaw had planted them along-side similarly cool loving giant Himalayan lilies (Cardiocrinum giganteum) in his Morgan Stanley garden. They were on show in the Great Pavillion too, most notably on the display by that most wonderful of Scottish nurseries, Kevock. I am afraid that, as warmer, drier climes push north, Scotland, and maybe some of the cooler parts of the Lake District will become the last refuge for this much-loved member of our garden flora.

For me, the South Africans dominated the great pavilion again. Tall grasses such as restios played foil to proteas, agapanthus, kniphofias and the brightly coloured southern heaths. Pelargoniums, another of South Africa’s inexhaustible contribution to our gardens, were on show in all their finery too; both the interesting species and a plethora of cultivars. I often see red pelargoniums, left in an unattended window box, doing well after a mild winter, and my own Pelargonium cordifolium v. rubrotinctum is left in a sheltered spot year-round. I wonder, in the future, will this be the standard rather than the exception to the rule? Certainly, South Africa will have more to offer British gardeners as time goes on.

The Chelsea flower show still leads when it comes to gardening fashion, but I think the trend we all need to be looking to for the future of Britain’s gardens will be lead by our changing climate. We need to be brave in our gardens, especially given the unpredictability of the issue in hand. It’s an envelope I feel needs to be pushed, and I intend to be there at the front of this charge.

Robbie Blackhall-Miles is a plantsman and conservationist. He tweets as @fossilplants.

