25th April 2020
by Peter Coles
It’s been four months since I last posted anything here – sincerest apologies. But I have been busy, despite the silence, and despite the lockdown. Here is a resumé of what I’ve been up to – and what mulberries have been up to – in London since the end of last year.
Midweek Mulberry virtual walk in Kensington Gardens
I had rescheduled a Midweek Mulberry walk for mid-April in and around Kensington Gardens, now that the wet and dark winter days have passed. But Covid 19 has put a stop to these, at least for a while. Not to be defeated, though, I thought I'd post some images and a discussion of what we might have seen.
Row of white mulberries along Mulberry Walk in Kensington Gardens
There are few better places in London to get up close to mature black mulberries (Morus nigra) as well as the much rarer (in the U.K.) white mulberries (Morus alba) than the park’s Mulberry Walk. On either side of the path, which runs along the wall forming the boundary between the Park and Palace Avenue, is a double row of mulberries – 14 white on the east side and 8 black on the west (wall) side.
Detail of Kesington Gardens from 2016 Royal Parks Management Plan
I understand that these mulberry trees are now part of the National Mulberry Collection, curated by Mark Lane, Garden Manager to the Queen at Buckingham Palace. Mark is not responsible for these trees, though, which come under the aegis of the Royal Parks and its Kensington Gardens team of arborists.
The white mulberries in Mulberry Walk are relatively recent – some are newly planted, others already 20 feet tall – but the black mulberries are all mature. I don’t have an exact date for when either might have been planted, but the black mulberries look as though they are 50 or so years old and are definitely post-war plantings, so no older than 75 years. If any readers have more information, please let me know and I’ll set the record straight.
During World War II parts of the Park were requisitioned for air raid schelters and 'Dig for Victory' allotments. In the 1970s Dutch Elm Disease also changed the landscaping, while storms in 1987 and 1990 damaged several avenues of trees. The second half of the 20th century has therefore seen some major tree (re)planting schemes and both rows of mulberrieshave been part of these.
Some Mulberry Botany
Unlike most of my Midweek Mulberry walks, this one was going to be oriented more towards the botany of mulberry trees. My idea was to lead a walk in each season – a Winter one for the buds, bark and overall shape; a Spring one for the flowers and leaves; a Summer one for the fruit; and an Autumn one for the striking, golden colour of the leaves.
As we couldn’t do either the Winter or the Spring walk, I thought I’d share a few photos of what we might have seen. If I still can’t lead a walk in the Summer – which would be a real shame – I’ll write another illustrated blog then.
In Winter it can be hard to tell a black mulberry from a white. For starters, though, almost all old U.K. mulberry trees are black, (M. nigra). Perhaps the only true veteran white mulberry (M. alba) in the U.K. is in the Oxford Botanic Garden, and dates back to the late 18th century. Mulberries in general are rare trees in Britain, and white mulberries very rare. In winter the only other tree they might be confused with is the Catalpa or Indian Bean Tree, which, from a distance, can also have the spreading, collapsed appearance of an old mulberry. But that’s about the only resemblance.
The buds of all mulberry species are alternate along the twig. Black mulberry buds are dark brown; white mulberries a slightly lighter shade.
Morus nigra buds (Photo Peter Coles)
The bark of both black and white mature mulberries is ridged, with furrows running up the stem, and has a slightly orange tint. The white mulberry is rather lighter in colour than the black.
Mulberry bark is ridged and has a slightly organge tint.
Left: Morus nigra (Photo: Peter Coles) Right: M. alba (Photo: Wikicommons)
Leaves and flowers
The 1st century AD Roman natural philosopher, Pliny the Elder, dubbed the mulberry (as it happens, the black mulberry)“the wisest of trees”, as it only puts forth its leaves when the risk of frosts has passed. But, claimed Pliny, when the leaves do emerge, they do so “in a single night and with a veritable crackling.”
I’m not so sure about the truth of either claim, but if ever there were a time to test his assertion about the noise, it would be in the new-found silence of London’s lockdown. In England the buds open in late March / early April, but with global heating leaf flushing is getting earlier. Most mulberries will already be starting to leaf by now.
Morus nigra leaf opening (Photo: Peter Coles)
If you’re able to get out for an exercise walk and live anywhere near a mulberry tree (look at the map on this site to locate your nearest mulberry), now is a great time to see not only the first leaves emerging, but also the flowers.
Left: Morus nigra female flowers Right: Morus alba male flowers (catkins). Photos: Peter Coles
Mulberries don’t have flowers with petals, like cherry or apple trees; they have catkins. Most mulberry trees – in particular black mulberries – are monoecious, which is a fancy word that means that both male and female flowers are on the same tree. In Greek, mono means 'single' and oikos means 'house'. So they “share the same house”. Some mulberries are dioecious though (the fruit appear on separate trees). Once they have released their pollen, the mail catkins will shrivel and fall to the ground. The female flowers will go on to produce fruit, whether or not they have been fertilised. The 'berries' are technically called aggreate or compound drupes, as each little bobble contains a seed from a separate ovary.
If your mulberry never produces fruit (and isn’t a sapling) it might just be bad luck, but chances are it’s a male tree. And if you don’t like the fruit, or the purple mess they make, you’d be happier with a male black mulberry, if you can find one.
More on leaves
The coming weeks, as we segue into summer, will also be a great time to learn the difference between the leaves of white and black mulberry trees. This isn’t so easy as it might appear from textbooks and field guides. While the shape of the leaves of the two main species is generally different, there are many caveats. A far more reliable key is the feel of the leaves.
The leaves of the white mulberry are light green, glossy and smooth to the touch. Those of the black mulberry are matte and coarser, because of thousands of tiny hairs on the underside.
This difference could be the main reason why silkworms are said to prefer the leaves of white mulberries (their only food). In fact, the silkworm (Bombyx mori) co-evolved with the Chinese white mulberry, but experience has shown that they will grow very well on a diet of black mulberries, though the silk they produce will be less fine.
The shape of mulberry leaves is far less straightforward as a cue to identification. The leaves of the black mulberry on old wood are generally heart-shaped, with deeply serrated edges. Equivalent leaves on a white mulberry (M. alba) are more ovate, or at least have a flatter base, and are less deeply toothed. But even this difference isn’t always apparent, for two reasons.
The first is that, while black mulberries have almost no cultivars or variants, there are hundreds of different white mulberry taxa, with massively different leaves. The second reason is that the leaves of both M. alba and M. nigra can be deeply (and irregularly) indented or lobed. They can even look more like fig leaves than what we think of as a mulberry leaf. These indented leaves are quite common on new growth (especially suckers near the base of the tree) and on young trees. It’s possible to find 20 or more different leaf shapes on a single tree.
Different Morus alba leaf shapes can be found on the same tree.
Some M. nigra leaves can also be deeply incised, especially on young shoots at the base of the tree.
(Wkimedia Creative Commons)
I’ll discuss leaf shape in a summer blog, when the differences will be easier to see on the trees. But in the meantime you can also refer to my book, which also contains loads of information on the different mulberry taxa and their various migrations, as well as references to mulberries in art, myth, literature and medicine.
In a few days I'll post Part II of this Spring round-up, with a preview of some of the fascinating research I've been carrying out with colleagues in Chiswick and at Syon House.
In the meantime, if you can safely include a mulberry tree in your outdoor exercise, I hope this botanical introduction will be of some use. Take care.
Unless stated otherwise, all text and photos (c) Peter Coles
This blog post has been made possible by a research development grant from Goldsniths University, Department of Sociology to Peter Coles and Professor Les Back.
 The white mulberry was unknown to Pliny and only arrived in Italy in the early 15th century.
 See the Royal Parks Kensington Gardens Management Plan 2016 for an overview. https://www.royalparks.org.uk/__data/assets/pdf_file/0006/41766/Kensington-Gardens-Management-Plan-16-26.pdf
 (St James’s Park and Greenwich University’s Stephen Lawrence library grounds are two others place that spring to mind where you can find both species).