Beneath June’s lush green canopy, London’s trees tell stories—from the gardenia-scented false acacia (a Tudor import) to the purple Pissard plum shading royal parks. High above, tulip trees hide waxy blooms, while Indian bean trees stretch their late leaves toward the sun. But the real magic lies in the details: the warty twigs of silver birch, the jagged teeth of black mulberry leaves, the hidden brown tufts that reveal a true English lime.
Why did Britain’s native oaks evolve such different leaves? Which tree’s flowers smell like honey and coffee? Return June 17 to decode the arboreal secrets woven through London’s streets.
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Trees
June is when trees are at their greenest. Their leaves are now fully expanded and many are getting gradually deeper in colour and covering any gaps still left in the canopy. Even the leaves of the last trees to break bud such as ash, honey locust and the Indian bean tree, are all now fully expanded. Trees commonly seen in flower this month include the tree of heaven Ailanthus altissima, Indian horse chestnut Aesculus indica, Kentucky coffee tree Gymnocladus dioica, Caucasian wing nut Pterocarya fraxinifolia, medlar Mespilus germanica and the false acacia Robinia pseudoacacia, with its rich scent of gardenias.
Late magnolias and tulip trees Liriodendron tulipifera also have large, waxy flowers that can easily be missed as they are produced tantalisingly high on the trees. At the beginning of the month many laburnums and red horse chestnuts may still be in flower as well as holly, box, rowan and sycamore. Although not flowering, ‘purple trees’ now stand out in London’s streets and parks. These are mainly the Pissard plum Prunus cerasifera ‘Pissardii’, purple beech Fagus sylvatica purpurea, Norway maple Acer platanoides ‘Crimson king’ and purple sycamore Acer pseudoplatanus Atropurpurea, all of which have striking purple foliage.
This is also a month to examine tree leaves more closely as many species, cultivars and varieties are all much easier to identify from their leaves alone. The new growth on firs, spruces and yew trees all stand out as a fresher, lighter green against the old, dark foliage.
The leaves of our two native wild oaks are also now easy to separate, the sessile oak Quercus petraea having a distinct petiole and the English oak Q. robur having virtually none at all. Similarly, our native silver birch Betula pendula and downy birch B. pubescens are often confused. At this time of year the leaves of silver birch are more triangular and have a longer point than those of the downy birch, also the twigs of the former have warty glands and those of the latter are downy. Black mulberries may also now be separated from white mulberries.
The leaves of the former have more slender tips and much larger, almost jagged teeth along their edges. Lime trees can also generally be troublesome to separate. The native small-leaved lime Tilia cordata has brown tufts of hair in the axils of the veins on the underside of their leaves. Large-leaved limes T. platyphyllos have very large leaves, perhaps twice the size of most others.
Silver limes T. tormentosa have noticeably silvery undersides to their leaves and the rarer Caucasian lime T x euchlora does not have the signature heart-shaped leaf but looks more like a poplar leaf. The most common of all in London’s streets is the common lime or European linden T x europaea which tends to have more asymmetrical leaf bases than the rest.
