Everyone knows about London’s trees, don’t they? Those magnificent London Planes, with the bark that peels and protects the tree from pollution. There are long avenues of them in Green Park, along the embankment, and in squares and parks around the city. But I’m not sure many of us really stop to notice these trees, let alone that they’re just one of the many species in our urban forest.
London Planes aren’t native to Britain, and were either brought over from Spain in the 17th century, or bred in London around the same time. Many of the trees we see in the streets today are a couple of hundred years old, dating back to their original arrive here. They are a hybrid, probably of the Old World Sycamore, Platanus orientalis, and the American Plane, Platanus occidentalis.
What makes them particularly London-friendly is that bark, which flakes off in large chunks to reveal a bright camouflage pattern underneath. This means air pollution cannot stick to the tree: something that’s still useful in our congested capital today, but was all the more necessary when the Industrial Revolution thickened the skies of the city. It also happily submits to human mistreatment, from thriving in the compacted soils under urban pavements, to responding well to being pollarded, or cut back heavily, when it is taking up too much space.
Next time you’re in a London street, have a good look at the Planes around you. Their bark can be surprisingly bright when it is newly-exposed, and their fruits look like Christmas baubles. Some specimens can develop rather outlandishly stout trunks, which make them look like British equivalents of the succulent baobab tree. Some of the best ‘baobab planes’ grow by the Imperial War Museum. In the autumn, the thick fleshy leaves are flattened onto the roads into a screen print.
But there are so many other incredible street trees thriving amongst the Planes. A similarly pollution-tolerant tree that grows among the central London Planes is the Indian Bean Tree, Catalpa bignonioides. There are many in Parliament Square and on the parliamentary estate too: these trees have wonderfully gnarled bark that looks like an Arthur Rackham illustration. They have heart-shaped leaves, long, hanging seed pods and sweet-scented white candelabra blossoms, and their blooming often seems to coincide with periods of particularly bizarre behaviour amongst MPs.
Another intoxicatingly-scented street tree is the Mimosa, Acacia dealbata, which announces its presence long before you’ve seen it. This tender tree likes the warm microclimate of the city. It has acid yellow foamy flowers in late winter, and feathery, deeply-divided leaves. Flowering even earlier than this is the winter-flowering cherry, Prunus subhirtella. This sets up its stall in late autumn and you can find the delicate pink-white blooms all the way until February. It often looks so out of place in the grey streets that passers-by tend to assume that it is responding to climate change, rather than flowering at its natural time. The Prunus genus contains those normal spring-flowering candyfloss-style cherries, too, as well as early-flowering species like Blackthorn (Prunus spinosa) and Cherry Plum (Prunus cerasifera).
All these trees have to grow in rather challenging circumstances. They are often too far apart from one another to grow supportive root networks, which allow them to share food and warn one another of attacks from insects, humans or animals. The soil around them is repeatedly flattened by the pounding of hundreds of feet on the pavement hour after hour. In drought, they have to keep their wits about them to survive. And yet they grow into old age regardless.
Once you start noticing London’s street trees, it’s hard to stop. There’s a wonderful map here of the different species you might be able to find, and there’s even a blog, The Street Tree and two books (London’s Street Trees and London is a Forest, both by Paul Wood) dedicated to these tough plants. You can download apps from the Woodland Trust to help you identify trees. It’s often not just about the leaves and the bark, but the twigs and the way the buds are arranged on them, too. And when you do start looking at these features, you’ll realise that the Plane Tree may have beautiful bark, but so does the Spanish Chestnut, Castanea sativa, which looks like a cable-knit sweater. You’ll notice that cherry leaves in the autumn look like goldfish hanging along a rod, and that Hornbeans have beautifully ornate pale green spring flowers. Soon, you’ll wonder how on earth it was that you ever assumed that London was a plain city for trees. It’s far more than just Planes.