The past couple of weeks have really brought home the power and immediacy of global heating. We've seen torrential rainfall here, wildfires all over southern Europe and stark headlines warning of a bleak future. The Met Office confirmed that Britain is already in the grip of climate change and pointed out that the 10 warmest years since records began have all occurred since 2002.
A few days later the UN’s IPCC report made clear that melting ice caps and rising sea levels are going to be with us for generations to come even if we keep the rise in temperature since the pre-industrial period to 1.5 degrees.
Like any national emergency, this one needs to be met with urgent change from ordinary citizens as well as from national and local government. That’s where you, the volunteers of Herne Hill Tree Watch, come in. The trees we nurture will capture carbon from the atmosphere, provide shade and cooling, restore threatened wildlife and protect against flooding.
We now have to keep up the rate of new planting, safeguard our mature street trees against loss and choose species that are fast-growing, adaptable to a more extreme climate and friendly to birds and insects.
Trees lost in 2021
We’ve lost quite a few trees recently, but none by neglect. Here’s the list we’ve come up with, in order of street name, but please let us know if we’ve missed any. Most of these (apart from the birch and sweet gum) were mature trees and we’d been monitoring their health for some time.
53/55 Casino Avenue, on the grass verge: a hybrid cockspur thorn (Crataegus x lavallei).
83 Casino Avenue, also on the grass verge: a rowan (Sorbus aucuparia).
Elmwood Road: a young Himalayan birch (Betula utilis jacquemontii) at the corner of Wyneham Road, outside 20 Elmwood. This had been getting exactly the same care as the other young birches on the street. It was cut down in early August after it unluckily died.
101 Herne Hill: a London plane (Platanus x hispanica). This was felled a few months ago and the stump removed.
1/3 Holmdene Avenue: a hawthorn (Crataegus monogyna). This was cut down in April due to extensive basal decay.
18/20 Holmdene Avenue: a newly-planted sweet gum (Liquidambar styraciflua 'Worplesdon'). The stem was snapped in July 2021.
15 Wyneham Road: a rowan (Sorbus aucuparia 'Joseph Rock'). This is to be removed. It died from silver leaf fungus and structural damage.
We’re hoping to get agreement with the council on a programme for replacing these and other lost trees in the coming November-March planting season. There are also eight trees which had been scheduled for planting in 2020-21 but missed the deadline. Those should all be carried forward.
Cleaner Greener Safer locations
You’ll recall that we were awarded funds totalling £17,000 from Southwark’s Cleaner Greener Safer fund to use this winter on planting 30-plus trees in new locations. Together with our street leaders we’ve identified potential planting sites for all of these and we’ll publish a list on the website shortly. We’ll let you know by a separate email when this is out and ask for your comments.
So there should be four planting streams in 2021/22:
Replacements for trees lost in recent years.
Scheduled trees that were held over from last season.
New trees funded by our CGS awards.
Other trees planned by the council, including the 10 Yoshino cherries in Winterbrook Road that we reported on last month.
Late summer blossom
There’s not much in the way of blossom at this time of year, although the little Persian silk tree (Albizia julibrissin) on the corner of Half Moon Lane and Village Way is just beginning to display its fragile, feathery, pink and white flowers. It’s definitely worth a visit, but for the full Albizia experience you should walk down to the Crown and Greyhound in Dulwich Village to marvel at the big silk tree on the grass verge outside the pub.
Another favourite of ours, the vivid pink hibiscus (Hibiscus resi) at 31/33 Beckwith Road, is also blooming beautifully this year, but there are two more hibiscus trees on Delawyk Crescent, outside no. 45. Their abundant flowers look a little paler, with a blueish tinge, and they’re at their peak right now. Try to see them before they fade.
At the top of Casino Avenue, meanwhile, the young Chinese privet (Ligustrum lucidum) planted last winter outside 27 Herne Hill is also coming into bloom. Its fragrant creamy flowers, in upright clusters known as panicles, should stay on the tree until January, setting off the glossy evergreen leaves. They'll be followed by little black berries.
There are three more tall Chinese privets on Milkwood Road, on the narrow pavement behind Pizza Express, that are already in full flower. They’re relatives of the native common privet (Ligustrum vulgare) that was a mainstay of suburban front garden hedges all over Britain before many of them made way for parking spaces or more exotic shrubs.
Great trees of Herne Hill: Indian bean tree
You might have been lucky enough in July to catch the stunning blossom on Herne Hill’s three Indian bean trees (Catalpa bignonioides), all of them on grass verges in the Sunray Estate. There was a spectacular display on the one outside 113 Sunray Avenue, just up from St Faith’s church.
Bunched together in cone-shaped heads, the glorious white flowers are marked with purple and yellow inside.
The enormous leaves of the bean tree are impressive too: heart-shaped with a pointed tip, they can reach 25 cm (10 inches) in length.
If you missed the blossom you can still enjoy looking at the catalpas’ exotic-looking fruit. These long, thin capsules, like bean pods, are just emerging and will hang on the branches most of the winter, rattling in the wind. You’ll be able to see them best if you visit one of the pretty cul-de-sacs off Casino Avenue - the one that’s nearest to the top of the road. Outside no. 35 stands a magnificent Indian bean tree, big, wide and low-hanging, that’s already bearing the aubergine-coloured fruit that will grow up to 40 cm (16 inches) long.
It’s a very stately specimen in a fine setting, and low enough that you can see the leaves, fruit and flowers close up when they’re in season.
And if you stand underneath the shady leaf canopy you’ll appreciate the bean tree’s size and strength.
In the next cul-de-sac down the hill stands the third Herne Hill bean tree, outside no. 87. This little one was only planted in May this year but still managed to produce a few clusters of flowers.
How trees are named
The beanpod-like fruit explains the ‘bean’ in the Indian bean tree’s common English name and the ‘Indian’ refers to the Native American people in the south-eastern United States where it originated. But colloquial names can be misleading. The hop hornbeam isn’t a true hornbeam, for example, the witch hazel is nothing like a hazel and the false acacia is self-evidently not a genuine acacia.
If you ask Americans to show you a sycamore they’ll point to what we call a plane tree. And if you want to buy a Davidia involucrata, the tree with brilliant white leaf-like bracts that had a brief and unhappy life at the Half Moon Lane end of Elmwood Road, you’ll find nurseries list it as dove tree, handkerchief tree, pocket handkerchief tree or ghost tree.
If you’re serious about trees you’ll soon get to learn the official botanical name. It will help you navigate tree guides, identify trees on the street or in the wild and get to know their close relatives. And it’s the same name all over the world, which is vital for growers, planters, environmentalists, researchers and commercial operators who all work across international borders.
The bean tree’s official name, Catalpa bignonioides, is a bit of a mouthful but it makes a good starting point for learning about the naming convention. The first word of a botanical name - in this case Catalpa - is what's called the genus. There are eight recognised catalpa trees in the genus, so Bignonioides is what distinguishes this one from the other seven. Together, the two names make up the species.
There can also be a third name to describe a cultivated variety, so if you spot an Indian bean tree with bright yellow-green leaves that will be a Catalpa bignonioides ‘Aurea’. And in tree books you’ll also discover that the genus Catalpa in turn is just one of 79 genera in the wide Bignoniaceae family of related flowering plants.
This naming system is known as botanical Latin, but in fact there's not much classical Latin about it. The bean tree, introduced into gardens in 1726, was given its botanical name by Thomas Walter, an 18th century British-born botanist who lived and worked in South Carolina. Catalpa is derived from ‘Catawba’, a local Native American tribe, while bignonioides, using the Greek suffix ‘-oides’, indicates ‘resembling a Bignonia’, a type of flowering plant. Bignoniaceae, then, means a family of Bignonia-like genera.
Species names can commemorate an individual, like this one, refer to the place where the tree originated or the habitat it grows in, or describe the leaves, flower, colour, shape or fragrance.
So where does the ‘Bignon’ bit come from? Well, the genus Bignonia was first named in 1694 by the French botanist and plant collector Joseph Pitton de Tournefort in honour of his patron Jean-Paul Bignon, the royal librarian to Louis XIV. And this takes us full circle: Tournefort himself was one of the pioneers of botanical classification, or taxonomy, where every plant is grouped into species, genus and family.
This system, expanded and refined by the Swedish naturalist Carl Linnaeus in 1735, is precisely the one we still use today. Every single plant fits into it. Among our more common native trees, the English oak species is Quercus robur, within the genus Quercus (the oaks) and the family Fagaceae, which encompasses a thousand species of beeches, oaks and chestnuts. They’re all linked by the nuts that they bear.
The silver birch is Betula pendula, its genus is Betula (the birches) and its family is known as the Betulaceae. Other members are the alders, the hornbeams and the hazels, and what they have in common is male catkins and female flowers on the same tree.
The Rosaceae family includes the cherries, plums, almonds, apricots and peaches (the genus Prunus), the apples (Malus), the pears (Pyrus), the whitebeams and rowans (Sorbus) and the hawthorns (Crataegus). Roses are part of the same family too, and the feature that connects them all botanically is the structure of the flowers.
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