20-May London’s May Trees: Secrets of the Urban Canopy
Summary
As spring deepens, London’s trees transform into living theatres of colour, scent, and motion. Lime trees shed delicate bud scales, creating fleeting pools of russet and gold beneath their boughs, while beeches unfurl silky new leaves so bright they seem lit from within. Conifers like Scots pine and giant redwoods release clouds of pollen—some grains even equipped with tiny “balloons” to ride the breeze. And in parks and woodlands, purple beeches, cherry trees, and smoke bushes flaunt their boldest hues before summer softens their shades.
Yet beyond the spectacle lie secrets. The ash tree, revered as the “Venus of the Woods,” was once believed to repel snakes and banish demons. Elms, Europe’s most enigmatic trees, defy identification with their tangled histories of cloning and hybridisation—though Battersea Park hides rare survivors, like the disease-defying Camperdown elm. Meanwhile, hornbeams and hazels dangle catkins like nature’s own decorations, and willow seeds drift through the air like slow-motion snow.
Article
Trees
May sees more trees coming into flower, others coming into leaf and some even fruiting or dropping their seeds. Lime trees all over London start the month losing their bud scales but by the end of the month they will have flowered and we will even see their fruits. Under many trees sufficient coloured bud scales will fall to form temporary pools of colour. Some birds even incorporate these delicate scales into their nests. In beech woods, such as Burnham beeches, the trees drop russet-coloured scales from their long, pointed buds. Then they may drop some protective leaves and finally the spent flowers. The leaves, when they first unfurl, are a bright, translucent green with silky hairs. Most of these hairs will be lost as the leaves gradually get darker and greener.
The new growth on many evergreen trees, such as holm oak, is now distinctly paler than the old leaves. Spruces stand out for the same reason. Scot’s pine, yews and giant redwoods are all now shedding copious amounts of pollen. When a branch is tapped, a shower of pollen can often be the surprising result. Clouds of pollen may even be seen drifting from conifer plantations. In the case of Scot’s pine, the pollen grains each have two minute balloons to help them on their journey. By the end of the month, most trees will have shed their pollen. Others, such as cherries, smoke trees, sumacs and maple cultivars are producing a range of red and bronze leaves which will later turn to green. The so-called ‘purple trees’ e.g. purple beech Fagus sylvatica purpurea, Prunus cerasifera ‘Pissardi’ and the various dark forms of maple, are all now showing their best leaf colour. Later, the intensity of purple will fade.
The most noticed seeds this month are those of willows, aspens and poplars which produce the slow-moving clouds of cotton seeds we sometimes see on warm, windless days. Elms and some maples are also covered in seeds, often brightly coloured in the case of Japanese maples. Different willows are still producing new catkins, although most are now seen spent in large numbers under the trees. Hornbeams and hazels produce catkins before their leaves, whereas birch, beech and oak produce them at the same time.
Ash trees have often been singled out for their beauty in May. Their fresh, green leaves are translucent and almost lime green and very late to unfurl. The tree is called the ‘Venus of the woods’ and her assistant Cupid made his darts from its wood. In one mythology, man was created from a piece of ash. Pliny believed an adder would rather go through fire than pass over an ash twig and in Scotland the sap was collected and fed to babies to expel demons. The wood, which will burn in the green, is said to smell of violets.
It is a brave field naturalist that attempts to identify an elm as they are justly regarded as the most difficult trees to identify in Europe. The reason for this is their natural promiscuity, readiness to hybridise and above all their propensity to form long-lived often isolated clones. As a group they have largely given up reproducing by seed in favour of suckering. Suckers from even a hedgerow elm can go on over time to form quite large populations of genetically identical elms. However, every now and again a seedling is produced which naturally is slightly different from both its parents. This can then go on to sucker and form a brand new slightly different clone. In places such as Buff wood in Cambridgeshire this process has continued resulting in 29 different clones being identified in the wood making it a mecca for elm enthusiasts.
When attempting to identify an elm it is important to only examine mature, fully opened foliage. Then you need to note the size and shape of the leaves, whether or not they are rough or smooth, how long the leaf stalk is and how prominent is the leaf tip. Other useful characters could include the shape of the tree, the size of any basal lobes on its leaves, to what degree the leaves are serrated and the presence or absence of any rusty-coloured hairs.
Fortunately, there are just two very common elms in London i.e. the Wych elm Ulmus glabra and the English elm U. procera. The Wych elm, a mature specimen of which can be found in Battersea Park, has large broad leaves over 7 cms in length which are rough to touch, have a long point and virtually no leaf stalk. It rarely suckers. In comparison the English elm suckers freely. It has smaller, darker leaves that are less than 7 cms in length and much more circular in outline. This is the elm that suffered most with Dutch elm disease so most are now dead and we just see the suckers that have survived, usually covered in a corky growth.
Other than these two native elms you occasionally come across two other rarer elms that have usually been planted. These are the Smooth-leaved elm U. carpinifolia and the Dutch elm U. x hollandica. Like many elms the Smooth-leaved elm is highly variable but its smaller leaves (less than 7 cms) which are longer, thinner and smoother than other elms can often help to mark it out. Dutch elms are hybrids between Wych elms and Smooth-leaved elms and come in many different forms. Their characteristics like many hybrids are often intermediate between their two parents. They may have large leaves like a Wych but not particularly rough to touch like a Smooth-leaved elm. There are a number of different types. For instance the Huntingdon elm U. x hollandica Vegeta is a clone typically found in the Huntingdon area and well-known for its broad fan-shaped crown.
A good specimen can be found in the Meadow area of Battersea Park. This tree has become much more widely planted due to its greater resistance to Dutch elm disease. Two other forms are the bright yellow U. x hollandica ‘Dampieri aurea’ which can be found near the Lido in Hyde park and a weeping form U. Hollandica ‘Wentworthii’ pendula which can be found in South Park Gardens in Wimbledon.
Two other elms worth seeking out are the Cornish elm U. stricta and the Camperdown elm U. glabra ‘Camperdownii’. The Cornish elm is best identified as a mature tree which is vase-shaped with steeply ascending branches reaching up to a narrow crown. It can be found in Regent’s park. The Camperdown elm is a weeping sport of a Wych elm first discovered in a forest near Dundee.
A handsome specimen of this can be found by the river in Battersea park which is though to have avoided the high flying beetle Scolytus scolytus responsible for Dutch elm disease on account of its small size. Over the centuries elm timber has had many uses. It was used to feed livestock and bed them down. Cowsheds were then made of it as it resisted constant kicking from the livestock. Later it was used to make water-pipes, hedges and the central hub of cartwheels. It was also a preferred wood for coffins and any switches made of it were though to confer good luck on the riders.
