Dear Readers, when you work with trees you have to have a long-term strategy, and never more so than in these changing times. At Kew, a recent study showed that up to 54 percent of the trees currently growing in the botanical gardens could be at risk by 2090, through a combination of rising temperatures, changes in rainfall patterns, biosecurity hazards and potential flooding. Some of our most familiar trees could be affected, including silver birch, horse chestnut, Scots pine, ash, larch, alder, oaks (both sessile and pedunculate) and even holly. Some of these trees will survive further north than their current range, and for some species there may be more resilient genotypes in other parts of the world, which have already adapted to hotter conditions. However, Kew is taking no chances, and may start to grow trees that are better adapted to the weather that we’re facing. Here are just a few of them.

First up, Iberian Alder (Alnus lusitanica). This is closely related to the Common Alder, but is more heat-resistant, and the hope is that many of the animals that currently rely upon it will make the jump to this species – it is often smothered in blue and great tits feeding from its cones in autumn  and winter.  Iberian Alder  could also prove to be a resilient street tree, though at the moment  Paul Wood (of London’s Street Trees) points out that a lot of Italian Alder (Alnus cordata) is being planted, even though it’s (whisper it) a bit of a boring tree outside of catkin season.

You can already see that Horse Chestnut is under stress, with a variety of insect and fungal attacks happening every year. Kew is thinking about using Indian Horse Chestnut instead – it seems to be more resilient to temperature, and the leaf miners aren’t so fond of it.

Scots Pine is clearly going to have a struggle, being a plant of open windy places with cold winters, but Kew is looking at a couple of possible pines, including the Stone Pine (Pinus pinea), which has a few examples in the roundabout outside Archway Station if you happen to be passing. The local pigeons seem to love the shade and can usually be seen in large numbers passing the time of day. This is where pine nuts come from, so maybe the pigeons are on  to something.

As all of our oak species are most likely going to be pushed hard as temperatures go up, Kew is looking at some more resilient species – while the oldest, best established trees will hopefully live out their life spans, it makes a lot of sense to grow related species that, again, some of our insects, fungi, galls etc may be able to use. One very unusual tree is the Holly Oak (Quercus baloot),  with leaves that look, well, like holly. As holly is also threatened maybe this tree could stand in for both (though of course for animals that feed on a plant it’s about much more than how it looks, ditto fungi.)

Holly Oak is an Indian tree, but another candidate is Quercus urbani, which is Mexican and is drought and  heat tolerant.

Quercus pannosa is a tree from Sichuan in China. I am honestly amazed at the variety of different oak trees out there. Let’s hope that some of them will take to the UK’s changing conditions.

So, it’s good that Kew is thinking about the future of the gardens. Unless I live to be 130, I won’t be around in 2090, but I like to think that although changing conditions may be too much for some of our species, at least in West London, others will thrive. What’s important is planning and adapting (and trying to do our bit to stop the worst ravages of climate change wherever we can, whether it’s what we do personally or what pressure we put on our governments, or preferably both).

And here’s one final tree that is, surprisingly, on Kew’s list of Resilient Trees. Yes, it’s my old favourite the Swamp Cypress (Taxodium distichum). I first met this tree in St Pancras and Islington Cemetery, and then  in the Cleary Gardens in the City of London, and from its green spring foliage to its rusty red autumn hues, it’s a spectacular tree. And as it’s in the woodland grave part of the cemetery, I like to think that it gives comfort to people who visit. It certainly does to me.