The days are getting shorter and the nights are getting chilly, but it's too early to say for sure that summer is almost over. If you think back to last September, the 10th was the hottest day of the year (peaking at 33.5° C) and the month as a whole was the joint hottest September on record. And some of our trees are still flowering even as August has come to a close.
We're going to take up the flower story where we left off in May, at the end of the traditional blossom season, and focus on some species that you might otherwise overlook. The trees are listed according to when their flowers appeared, first to last.
EARLY MAY Laburnum
There's a little laburnum on a strip of grass outside Sunray Gardens that puts on a pleasing display of bright yellow colours in late spring despite its slightly hostile environment. The site is near where the old phone box used to stand, next to the pedestrian crossing leading to Charter School. The soil here is very shallow and there's solid concrete not too far down. There was a second laburnum here but it died in 2020 and collapsed in a strong wind the following year. There's now a ginkgo (Ginkgo biloba) in its place, and if anything can flourish here it will be one of those.
The laburnum is, perhaps surprisingly, a member of the pea family (Leguminosae) along with garden peas, runner beans, horticultural staples like brooms, lupins and sweet peas, wild plants like gorse, and a few other trees that you'll find in Herne Hill: the honey locust, Judas tree, mimosa, false acacia, Japanese pagoda tree and Persian silk tree (we'll be looking at the last two later on in this blog).
What do these very different species have in common?
Roots with nodules that can 'fix' nitrogen, transferring it from the atmosphere to the soil, where it works as a natural fertiliser
Very distinctive flowers
Seeds in long pods
And, for the trees at least, compound leaves that are 'pinnate', meaning that each leaf is made up of 'leaflets' arranged on either side of a central stem. In some cases, like the mimosa and the silk tree, each leaflet is further divided into micro-leaflets called 'pinnules' which give the foliage a feathery look.
The flowers of the laburnum are typical of the pea family. There are five petals arranged in a way that's unique to peaflowers: one upright, two forming small wings, and two at the bottom joined together to hide the reproductive organs.
They tumble down in a cluster known as a 'raceme', a spike with many individual flowers growing on short stalks coming off a central stem. There's a simple sketch of a raceme here, on the very useful treeguideuk.co.uk website.
Just one caveat before you go out and plant a laburnum in your garden: its beauty is deceptive. Every part of the laburnum is poisonous to human and animals.
LATE MAY: Holm oak
The very fine holm oak (Quercus ilex) at the junction of Elmwood Road, Beckwith Road and Half Moon Lane is a big, dark presence for most of the year, its dense evergreen leaves giving a cooling shade to people using the popular bench below. For a few weeks in late spring, though, the tree lit up with sprays of pale yellow male catkins that transformed the scene.
The fertilised females are now producing a crop of small, pale green, pointy-
headed acorns, but our big deciduous oaks - the Turkey oak and English oak in the green space off Sunray Avenue - look like they'll be barren for the second year running. 2022 was a 'mast year' when oaks and the related beeches produced masses of seed (acorns and beech nuts) and they can take a long time to recover from that effort.
Holm oaks aren't native to Britain, but like other introduced species such as sycamore, common horse chestnut and sweet chestnut they've become naturalised, which means they spread readily in the countryside. Their dark, glossy leaves can sometimes have spines along the edges, which explains the botanical name (Quercus = oak, Ilex = holly).
LATE MAY: Indian horse chestnut
It's unusual to see the well-loved common horse chestnut (Aesculus hippocastanum) being planted these days. They have a lot of health problems and many of them have been removed in Dulwich and Herne Hill.
One of the preferred substitutes is the related Indian horse chestnut (Aesculus indica), which has been shown to be resistant to the very damaging horse chestnut leaf miner. The pretty white flowers grow in stiff, upright clusters that botanists call panicles. They're different from racemes like those of the laburnum (above) in one important sense: rather than having single flowers growing out from a central stem they have other little multi-flowered racemes, as this diagram shows. Each of these mini-racemes has its own cluster of stalks and flowers.
But the flowers do take a long time to get going. By April this year the common horse chestnut and the resistant red horse chestnut (Aesculus x carnea) were already covered in their familiar 'candles'. But all the Indian horse chestnut had to show for a few weeks were naked, skeletal flower spikes. The buds finally opened in late May.
The flowers and foliage of the Indian horse chestnut are undeniably attractive, but could their dark, shiny nuts one day replace the old-fashioned conker in the hearts of British schoolchildren?
There’s more information about flower clusters, including panicles and racemes, at https://www.treeguideuk.co.uk/inflorescences/.
LATE MAY: tulip tree
The tulip tree (Liriodendron tulipifera) is an increasingly common sight on our wider residential roads. It's from the same ancient tree family (Magnoliaceae) as the magnolias and like them has primitive features dating back 95 million years to the Cretaceous period. It's not just the extraordinary four-lobed leaves, squared off on top, which are unlike any other tree on earth.
The flowers, too, are one of a kind. They unfold pale yellow, green and orange in early summer, dotted around the high crown of the tree in ones, part-obscured by the foliage and difficult to spot unless you can get close up with a zoom lens.
The pretty flowers eventually develop into green fruit composed of layers of stacked-up samaras, each samara an airborne transportation system for the single seed cargo they carry. In winter, when the samaras have all blown away, the woody bones of the fruit remain among the bare branches for months.
MAY TO JULY: Himalayan birch
Every tree produces flowers, but not all of them are the kind that you might see arranged in a vase. The birch family (Betulaceae) - birches, alders, hornbeams and hazels - reproduce with catkins instead and are all 'monoecious', meaning that the male and female catkins grow on the same tree. The males, clusters of tiny flowers, appear first in twos or threes at the ends of the bare shoots, but once their flowers open in springtime and early summer to release their pollen they turn brown and fall. The pollen can travel long distances, which may explain why birches are 'pioneer' trees that rapidly populate bare soils.
The smaller, less conspicuous green females only increase in size once they've collected pollen brought in on the wind. The white-barked Himalayan birch (Betula utilis jacquemontii) shown here is the most widely planted of our many birches in Herne Hill. Over late summer its female flowers develop into dark brown fruits that look like miniature pine cones, full of seeds that bluetits love to peck at. Each 'cone' dries out and curls open up in the autumn, letting go of masses of seeds that fly away on little wings. The empty cones can remain on the tree for months, side by side with the new season's male catkins.
EARLY JUNE: Limes
The whiskery white flowers of our limes are modest little things, but they make up for their limited charms in two ways: first, with their sweet fragrance, one of the signals that summer's really arrived, and second, by covering the trees in riotous profusion in June. And it's not just the flowers: even when they've faded away the jolly dangling seed balls and the pale yellow bracts (modified leaves shaped like tiny skateboards) persist right through August.
Whether it's the native large-leaved lime (Tilia platyphyllos) pictured below, or the exotic Mongolian lime (Tilia mongolica) with its deeply cut leaves, all the lime species on our streets put on a great show. By autumn, the dried-out bracts will help the seeds fly away on the wind and keep the show on the road for future generations. And in the meantime we can watch the six new limes planted this season as they grow to maturity.
JUNE TO AUGUST: Hibiscus
Two new hibiscus (sometimes known as Rose of Sharon) were planted towards the Half Moon end of Elmwood this year, making three altogether on the same street. Each of these Elmwood trees is the Hibiscus 'Resi' cultivar, which carries long-lasting pink, lilac or mauve flowers in summer. Hibiscus is originally a tropical tree or shrub, but the varieties grown here are hardy and seem to appreciate our recent hot weather.
Nurseries grow hibiscus as a hedging plant, a shrub or a standard tree (one with a single stem), although from our experience the stems do lean a lot as they mature and need to be supported by stakes for a long time. They'll never grow to more than four or five metres high.
There are two more 'Resi' on Delawyk Crescent, on the grass at the side of no. 45, and at 31-33 Beckwith Road stands an older hibiscus that produces exceptional wine-coloured blooms. We think it's a Hibiscus syriacus ‘Woodbridge’. It was still putting on a fine display in the first week of September when the other hibiscus trees in the area had already lost their flowers.
JULY: Indian bean tree
We covered the big Indian bean trees of Casino Avenue and Sunray Avenue in some detail in August 2021 and three years later they can still amaze us when their prolific panicles of big white flowers emerge in July. And when the flowers fade, remarkable seed pods (the 'beans' of the common name) take their place, olive green at first then dark brown and growing to up to 40 cm long until they split open in spring to drop their seeds. They're probably the last tree to come into leaf, not long before the flowers themselves.
Our most magnificent bean tree is at the end of the the top cul-de-sac on Casino, outside nos. 33-35, and until June there was another further down the road, on the corner at 85-87. It was a pretty yellow-leaved type called Catalpa bignonioides 'Aurea', only planted in 2021 but knocked over by high winds on June 16 this year. The tree officers say it will be replaced like-for-like.
JULY: Pride of India
Another new flowering tree is the Koelreuteria paniculata (Pride of India or Golden rain tree) planted in March on the traffic island outside Brockwell Park after winning a public vote. It will never be as big as the sycamore that it replaced, but it does offer pretty red and yellow flowers in spring, attractive lobed leaves and extraordinary seed-bearing fruit in the autumn.
The biggest Koelreuteria in the neighbourhood is in the grounds of Judith Kerr School, one of the many large and beautiful trees there that are covered by TPOs (tree protection orders). You can see it from over the fence outside 2 Village Way.
Its branches glow yellow in July when the flowers are at their peak, turn red in August when the papery seed-containing capsules develop, and ripen to dark brown in October. There's another Pride of India just inside the railings of Sunray Gardens at the end of Elmwood Road
JULY TO AUGUST: Southern magnolia
We looked at the glorious spring-flowering magnolias back in May, when the delicate petals had already been scattered by the wind. A month or so later, the only evergreen among this family of trees - the Southern magnolia (Magnolia grandiflora) - began a long flowering season that can sometimes run until the beginning of winter. Only a few flowers will show at any one time, but there will always be fat new buds ready to unfurl.
The fragrant white, silky-looking blooms measure up to 25 cm across but can be hard to pick out among the glossy, leathery leaves. Because magnolias evolved millions of years ago, before bees existed, they're pollinated largely by flightless beetles that eat the pollen.
There's just one Southern magnolia on public land in Herne Hill, on the lawn to the right of the Pynnersmead flats, next to St Paul's church on Herne Hill. But in summertime you can see a bigger one in flower, in the back garden of a house on Holmdene Avenue that's visible from the corner of Warmington Road and Howlett's Road.
When the flower dies off it leaves behind a very unusual ancient fruit, known as a follicetum. It looks a bit like an old-fashioned shaving brush to start with but soon develops a thick, whiskery husk housing bright bright red-orange seeds (Creative Commons licence: Coastside2, CC BY 3.0). In the autumn the husk falls away, leaving the seeds to be dispersed by birds and animals. (Creative Commons licence: Pmsyyz, CC BY-SA 3.0).
JULY TO AUGUST: Japanese pagoda tree
Here's the second of our trees from the pea family: the Japanese pagoda tree or Styphnolobium japonicum. Until a few years ago, when it was reclassified, this interesting tree was called Sophora japonica - much more pronounceable but botanically inaccurate. It actually originates from China, not Japan, but that's a detail we can overlook. Holmdene Avenue, which has the pavement and road width, is the local stronghold of these fast-growing, shade-giving, drought-tolerant trees that will withstand climate change well. The creamy-white flowers look like those of the laburnum, although they grow in spiky panicles, not tumbling racemes.
AUGUST: Persian silk tree
Our third member of the pea family is the Persian silk tree (Albizia julibrissin). We've paid a lot of attention to this tiny tree over the past six years, partly because of its stunning flowers but also because it seems to stumble from crisis to crisis. In 2024 it had its third infestation of scale insects in June, although of a different, smaller variety than the previous two attacks in 2022 and 2023. Once again they clothed the branches and kept them almost bare until the feathery leaves finally grew. This time round, they unexpectedly also sprouted from the base of the tree. Does that mean this Peter Pan tree is finally growing up? We're not sure. After all, its stem is still only about an inch (2.5 cm) in diameter.
Now what distinguishes the Albizia as a pea tree? It's not the fragile, silky, fan-shaped flowers that finally showed up in August this year - pink and white on the Herne Hill tree, red and white on the Dulwich Village Tree, both pictured below. It's not the way the flowers grow in racemes like the laburnum when there are enough of them. That's not a feature that's limited to Leguminosae.
But the pinnate leaves are one clue, and the other is the little peapods that the silk tree bears when the flowers have gone.
SEPTEMBER: Crape myrtle
In the coming week or two, keep your eyes open for panicles of pink flowers on the four new crape myrtles (Lagerstroemia indica 'Rosea') planted here in February and March. There are two on Danecroft Road (at nos. 28 and 68-70), one on Elfindale Road (at 85) and a fourth on Frankfurt Road (at 16-18).
By September 3 they weren't showing any sign of blooming, and it's possible that these new starters might in fact be too young to flower yet. Their bark, though, was peeling nicely to uncover shades of pale brown beneath.
Meanwhile the more mature crape myrtle on Crossthwaite Avenue outside Anijh Supermarket, just over the postcode boundary with SE5, had begun putting out flower spikes with plentiful buds (above). Here's what it looked like in full bloom in mid-September 2023.
There's a sixth local crape myrtle in the Delawyk Crescent estate, just behind the front lawn at the side of no. 54, but it's never really thrived. Have a look at these pictures on the Van den Berk nursery website to get a flavour of what to expect from these young trees in the next few years - not just flowers to cheer us up as summer draws to a close, but terrific bark colour and lovely autumn leaves too.
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