News that Ventnor Botanic Garden on the Isle of Wight has just planted the first citrus grove in the UK made the front pages recently, with the tabloids trumpeting an exciting future where we bask in year-round Mediterranean sunshine.
For Ventnor head gardener Wayne Williams, it is certainly an exciting experiment, but also a concerning indicator that our climate is changing, and changing fast.
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“This garden has always been an average of five degrees warmer than the rest of the British Isles,” he says. “We have had a few of the hardier citrus outside for the last 15 years, but recently conditions have become mild enough to give us the confidence to plant out a good range of lemons, oranges, grapefruits and Buddha’s hand citrus, as well as a rare caviar citrus (although that will probably have to come in over winter for the foreseeable future). I’m looking forward to the challenge, but I’m sad that we may not be able to grow apples in future.”
If apples are indeed unable to cope with our changing climate, that will be extremely bad news for Tom Brown. As head gardener at West Dean in West Sussex, he has responsibility for a renowned collection
of over 100 different varieties of exquisitely trained fruit trees.
“We have started losing apples,” he says. “I am not prepared to give up on them yet, but we are changing our practices to try and increase our chances of future success. When this orchard was planted 30 years
ago, we used dwarfing and semi-dwarfing rootstock to control vigour and help with the training regime. Today, when I am choosing a replacement, I go for M25 rootstock, which promotes much stronger growth. Trained forms are, by definition, under a lot of stress, and I’d rather control an excess of vigour than try to coax vigour out of a weakened plant. The big question for the future is how far we will be able to retain traditional features like this orchard or, for example, box hedging, in the face of changing conditions.”
In southeast London, head of horticulture Errol Reuben Fernandes is struggling with a similar conundrum at the Horniman Museum gardens. “We have a significant avenue of horse chestnuts, which has been affected by horse chestnut leaf miner overwintering in the trees and making them susceptible to bleeding canker, which in time could lead to branches falling unpredictably.
“We addressed this head on when we launched our Climate and Ecology manifesto in 2020, and this now guides all our thinking. I am just about to move our Prehistoric Garden, which was sited on top of a hill buffeted by wind and baked by sun, because our tree ferns can’t cope there without misting rings. We still want the tree ferns, but they are relocating to a site where I don’t have to irrigate them just to get them through a summer.”
Elsewhere in the gardens, Errol is experimentally pushing the limits of what he can grow, particularly in the Xerophytic Garden. “I have managed to get Salvia leucantha and S. discolor through the winter, and I am about to try my luck with Echium candicans. Watch this space…”
Over in Somerset, designer Dan Pearson has also noticed marked changes in the plants that thrive in his garden. “For 15 years, cimicifugas and acteas were my absolute favourites, but I have had to accept that I can no longer grow them here. During a nursery visit to the Netherlands last year, they were all saying the same thing as well. It is sad, because they were an important part of the autumn palette in my garden, although it is also an exciting opportunity to experiment.
“I am currently growing every phlomis on Olivier Fillippi’s nursery list, trialling them in my sand bed, a regular stock bed and on a hot dry slope. But some other plants that used to be fine at the top of the slope are now having to be moved down into more moisture-retentive parts of the garden. Persicarias and thalictrums were both having difficulties, and although my peonies still seem to be generally resilient, they are inclined to shabbiness in a way they never used to be,” says Dan.
I have had to accept that I can no longer grow my favourites. It is sad, although it is also an exciting opportunity to experiment
DAN PEARSON
“You have to keep an open mind and an observant eye. Even a few years ago, there was a general feeling that we would all soon be gardening in a Mediterranean climate, but now we are realising that the only thing we can really expect is the unexpected.”
James Hitchmough, who is based further south in Somerset, conducted a careful study of climate predictions before planting much of his own new garden recently, and he echoes this sentiment. “The other thing to point out is that we will have big variations around the UK. Even though we are a relatively small land mass, the southeast is expected to have a climate similar to present-day Barcelona. My own garden will probably be something like Brittany, but in Glasgow they may have the climate of South Yorkshire.
“This will definitely affect the plants we grow. Things with big soft leaves will probably be losers in the south, but still grow well in the northwest. We will all have to conduct our own experiments. I just planted
a border alongside the house and put in a Cyrtanthus obliquus. It’s a South African geophyte from the Eastern Cape, and I had it in my greenhouse for years, but it is hard to look after in pots, so I am risking it outside in the ground,” says James.
“Climate change offers an opportunity in the garden but is concerning on a global level. Most significant will be its impact on the trees we can grow, and this is one group of plants where we have a moral obligation to future generations to make the most well-informed choices that we can.” Our European ash, Fraxinus excelsior, is likely to struggle, but the southern European ash Fraxinus angustifolia could be a good alternative, he explains. If you have concerns about the viability of Cornus kousa, then consider substituting Cornus capitata or Cornus hongkongensis. There’s a useful climate tool developed by the Forestry Commission (climatematch.org.uk) that can help you plan.
Rowans and birches will probably struggle, but ginkgo, metasequoia and liriodendron are all likely to do well
DAVID KNOTT, ROYAL BOTANIC GARDEN EDINBURGH
David Knott, a curator at the Royal Botanic Garden, Edinburgh, is also rethinking his tree selections. “We are currently benefiting from trees that were planted hundreds of years ago, and we must think on the same scale now, but climate extremes are a big concern. Here in Edinburgh, we have had our hottest, coldest, wettest, driest and windiest weather on record over the past 15 years. That is a massive challenge for our plants.
“Within 30 years, we anticipate that our climate will compare to the south of England. That means rowans and birches will probably struggle, but ginkgo, metasequoia and liriodendron are all likely to do well.”
Nursery owner Derry Watkins is even more pragmatic. “There’s no telling with the weather and there really are no rules so, if you fancy growing something new, you might as well just have a go.
“I’m based in the South West and I propagate anything tender, so I have insurance, then leave the original plant out to see what happens. I am certainly getting away with things now that I never would have in the past,” she says. “My Digitalis canariensis survived last winter outside, and I’ve had an Eriolarynx australis outdoors for a few years. They are as tender as a petunia in their first winter, but seem to get tougher as time goes by. I have also successfully left Salvia ‘Phyllis’ Fancy’ and Salvia ‘Amistad’ out.”
In the end, like many gardeners, Derry is keen to try new things and remains sanguine about adapting to the situation. “I decided long ago that what will be will be, and there’s no point worrying about
it too much. I have always experimented. That’s the whole point of gardening.”