We're stepping out of Herne Hill for this blog, and making our way to the other end of the borough to have a look at a very special tree. It deserves our attention for two reasons. First, it's the 100,000th tree on Southwark council land (meaning pavements, housing estates and parks). That's more than any other London borough. And second, the tree officers have chosen a really distinctive species to mark this milestone: a giant sequoia (Sequoiadendron giganteum).
Well, we say 'giant', but at the moment it's just a baby by sequoia standards, only two or three metres high and around six years old, a fresh graduate from the tree nursery. In about 20 years it should reach about 13 metres (over 40 feet) in height and eventually - in urban conditions - grow to 50 metres (160 feet). Here it is at sunset on the day it was introduced to the public, on November 26, and on a cold, overcast afternoon in SE1 three weeks later:
Where can you see it?
Clearly a sequoia isn't something that would be suitable on the narrow pavements of Herne Hill, where its roots would rapidly chew up the roadway and its branches engulf the houses. But it's got loads of space to expand at its new home in Geraldine Mary Harmsworth Park, at the corner of St George's Road and Lambeth Road. Its nearest big neighbours there are actually the pair of huge naval guns that guard the entrance to the Imperial War Museum, the centrepiece of the park. Hop on the no. 3 bus if you fancy a visit.
Where do giant sequoias come from?
These amazing trees are native to the western flanks of the Sierra Nevada mountain range in California, where they grow in small, secluded groves. They were 'discovered' by white explorers, hunters and gold miners in the 1830s, 40s and 50s, although they were of course already known to the indigenous peoples. According to Hillier’s Manual of Trees and Shrubs, the tree is named after Sequoyah, a mixed-race Native American who invented the Cherokee alphabet. It's also colloquially known as the giant redwood, Wellingtonia or sierra redwood
They're among the longest-living trees in the world, capable of reaching an age of around 3,400 years, and the area they live in has been protected since 1890 as Sequoia National Park. One of the trees in the park - known as 'General Sherman' - is considered the world's largest living organism. It's around 87 metres (275 feet) tall and 31 metres (100 feet) around the base. Other sequoiadendrons in the region are taller (over 100 metres) and some have a bigger circumference, but it's the combined volume that makes the General unique. You can see more incredible statistics here.
Not content with just admiring or photographing these fantastic trees, for decades tourists in California have also been able to drive their cars through openings chopped into their trunks, like this one, the Chandelier Drive-Thru Tree in Leggett - one of three that unbelievably are still open for traffic. There were more of these chiselled-out sequoias at the height of 'Big Tree' mania early in the 20th century, but they soon fell down.
When did giant sequoias arrive in Britain?
While this is the first giant sequoia on public land in Southwark, it turns out that they're surprisingly popular throughout the UK, where they were introduced in 1853. Avenues of giant sequoias soon sprung up in the grounds of stately homes and specimen trees quickly spread to many ornamental parks and gardens. The New Scientist reported earlier in 2024 that they grow just as fast here as they do in their Californian mountain home and the biggest one - in Scotland - is already approaching 55 metres in height.
What do giant sequoias look like?
The Sequoiadendron is a conifer, a primitive and ancient form of tree that first emerged some 300 million years ago. As the name suggests, conifers bear woody cones to house their seeds, unlike modern trees which bear flowers and fruit. It's also evergreen, which may sound obvious except that some conifers, like the larch (Larix), do lose their leaves in autumn. The oval cones, about 6 cm long, stay on the tree in bunches until forest fires generate enough heat to force them open and release their seeds. Eucalyptus trees are similarly fire-adapted, reproducing with the help of wildfires.
In giant sequoias the fibrous, spongy, red-brown bark is thick enough that the tree can survive most fires, although its lower branches do get burnt off. However, when extreme fires are forecast some sequoias in the national park, including General Sherman, have in recent years been wrapped in protective aluminium foil.
Our very young tree has attractive, smooth, pinkish-brown bark with striking yellow markings. The scaly leaves, or needles, are grey-green on fresh shoots but get darker green as they age.
What else is there to see in Geraldine Mary Harmsworth Park?
The Imperial War Museum building originally housed Bethlem Royal Hospital for the Insane, the first psychiatric hospital in England, whose name became corrupted into 'bedlam', meaning ‘uproar and confusion’. But in 1930 the hospital moved to Beckenham, where it's now part of the South London and Maudsley NHS Foundation Trust, and the patient wings were knocked down to form the public park. The museum opened in the surviving central hospital block in 1936.
The park has a fine collection of trees but like many streets and green spaces in Southwark it’s dominated by London planes (Platanus x hispanica), including these terrific 'baobab planes' with their bizarrely swollen trunks resembling an African baobab tree (Adansonia). Click on the two photos for close-ups.
To celebrate its 100,000th tree the council held a reception inside the museum where Portia Mwangangye, the Cabinet Member for Leisure, Parks and Young People, said Southwark would be planting a total of 1,300 trees and 6,000 hedging plants across the borough in 2024-25. It had planted 290 tree species in the last five years.
Julian Fowgies, the Parks, Trees and Ecology Manager, told Herne Hill Tree Watch that
Southwark now had close to 20% tree cover, up from 17-18% five years ago. Its target is 24%.
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