Morus nigra L.

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Credits

Tom Christian & Peter Coles (2022)

Recommended citation
Christian, T. & Coles, P. (2022), 'Morus nigra' from the website Trees and Shrubs Online (treesandshrubsonline.org/articles/morus/morus-nigra/). Accessed 2022-10-07.

Genus

Common Names

  • Black Mulberry
  • Common Mulberry
  • 黑桑 (hei sang)
  • Mûrier Noir
  • Schwarze Maulbeere
  • Zwarte Moerbei

Glossary

clone
Organism arising via vegetative or asexual reproduction.
androdioecious
With only male or only hermaphrodite flowers on individual plants.
endemic
(of a plant or an animal) Found in a native state only within a defined region or country.
indigenous
Native to an area; not introduced.
latex
Colourless or milky sap produced by some plants (e.g. many Apocynaceae Euphorbiaceae Moraceae).
monoecious
With male and female flowers on the same plant.

References

Credits

Tom Christian & Peter Coles (2022)

Recommended citation
Christian, T. & Coles, P. (2022), 'Morus nigra' from the website Trees and Shrubs Online (treesandshrubsonline.org/articles/morus/morus-nigra/). Accessed 2022-10-07.

Tree 6–12 m tall with a clean bole or branching almost from the base, the lowest branches disposed to layering. Main trunk deeply fissured, often with many burrs; bark grey to dark brown. Crown dense, spreading, often wider than the tree is tall; mature trees often leaning, eventually collapsing and layering to produce new upright stems. Branches and branchlets densely pubescent. Stipules lanceolate, 2–3 cm, pubescent. Leaves broadly ovate, entire or 2–5-lobed, 15–23 cm long on vigorous sterile shoots (4–12.5 cm on flowering shoots); upper surface conspicuously rough with short, flattened hairs, deep glossy green; lower surface pale, downy; base cordate; margin usually regularly, coarsely serrate; apex acute to short-acuminate; petiole to 2–6 cm, pubescent. Male inflorescences 1 per node, 2–4 cm, peduncle 0.5 cm; male flowers with ovate calyx lobes. Female inflorescences 1 per node, to 1.3 cm long; female flowers with ciliate, ovate calyx lobes, styles much reduced (<1 mm) stigmas branched. Syncarps maturing dark red, purple or blackish, elliptic to ovoid, 1–2.5 × 1–2 cm. (Wu, Zhou & Gilbert 2003; Razdan & Dennis Thomas 2021).

Origins and distribution

Morus nigra has been cultivated for so long that its original distribution has become obscure. It is commonly thought to be native to the region bordering the southern Caspian Sea (today’s Iran, Azerbaijan, and Turkmenistan), where it would originally have been an isolated component of temperate deciduous forests (Grieve 1931). It has long been valued in the region for its fruit, known as shah-toot or ‘king mulberry’ in Farsi and several local languages, in contrast to the smaller, stalked, white or dark purple fruit on some M. alba taxa, which were introduced from Eastern and Central Asia and known simply as ‘toot’ (Coles 2019).

M. nigra is widespread in the Eastern Mediterranean, where it has probably been cultivated since antiquity. Linnaeus (1753) believed the species to be native to southern Italy, and it featured in the writings of 1st century AD Roman natural philosopher Pliny the Elder (Pliny 1945) as well as being depicted in mosaics buried under ash when Vesuvius erupted in 79 AD (which also killed Pliny) (Coles 2019). A Black Mulberry features in the tale of Pyramus and Thisbe by the 1st century BC Roman poet Ovid, where the red juice of its fruit is tragically mistaken for blood, leading to the double suicide of the two eloping lovers. Interestingly, the author set the tale in Babylon, south of present-day Baghdad (Iraq), where M. nigra may also be indigenous.

Meanwhile, some authors (Browicz 2000) argue that Greece (or rather the Hellenic peninsula) is the ‘true’ home of the species, hence Morea (Μορέας), the medieval name for the Peloponnese peninsula, which is shaped like a mulberry leaf, but there is no definite support for this claim. Black Mulberry was once abundant there, however, its leaves sustaining a silk industry from the 6th – 13th centuries within the Byzantine empire (Muthesius 1989).

There is some confusion regarding the presence of the species in Middle Eastern Antiquity. The Greek συκάμινος (sykaminos) of the New Testament of the Christian bible is usually translated into English as ‘mulberry’ but is likely to refer to another Moraceous species endemic to this region, the sycomore-fig (Ficus sycomorus) (Hehn 1891).

The discovery of mineralized M. nigra pips in Roman archaeological sites in Europe suggests that Black Mulberry was introduced into Gaul (southern France) and southern England around the 1st century AD, and parts of northern Europe and Scandinavia during the Roman occupations up until the 5th century AD (Lodwick 2017; Livarda 2008). It is not clear, though, whether the Roman colonisers cultivated the tree, or simply consumed its fruit, for example in syrups. The fragile fruit does not travel as it disintegrates soon after harvesting and cannot easily be dried. This was immortalised by William Shakespeare in his tragedy, Coriolanus (written around 1609): ‘humble as the ripest mulberry / which does not hold the handling’. As a rule, to consume fresh mulberries, one has to have a mulberry tree to hand. The earliest evidence for M. nigra cultivation in France dates to the 4th century AD, in the region of Languedoc (Durand et al. 2016).

There is more solid evidence for the cultivation of M. nigra (for its fruit) in northern Europe after the 11th century, although there is some confusion over nomenclature, as the Old English name ‘morbeam’ refers to both the mulberry and the blackberry (Rubus fruticosus) (Coles 2019). The Middle English word ‘murrey’ was used for the purple colour of the Black Mulberry fruit, from the French mûre, which also refers to both the Black Mulberry and the Blackberry. The 16th century herbalist John Gerard includes the Black and White mulberries in his Herbal (Gerard 1597, chapter 131).

M. nigra was introduced to the Iberian Peninsula from Syria by conquering Arabs during the 8th century along with techniques for raising silkworms for silk (sericulture) (Martínez 2000). The leaves of Black Mulberry, like other Morus species, exude a milky latex when cut, which may contribute to the elasticity of the silk thread that the silkworm (Bombyx mori caterpillar) spins around itself in order to metamorphose into a moth. Although the wild silk moth (Bombyx mandarina) evolved in China in symbiosis with M. alba – the leaves of which were its sole source of food – the domesticated silk moth, Bombyx mori, will adapt to a diet of M. nigra leaves if necessary. Indeed, M. nigra leaves sustained sericulture in the Middle East, Italy, the Iberian Peninsula, and France until M. alba was introduced from East and Central Asia in the early 15th century (Zanier 2019).

From the 11th century there are records of Black Mulberry growing in infirmary orchards of medieval monasteries in Europe and Britain (Coles 2019). The English naturalist and apothecary William Turner (1509–68) is credited with planting Black Mulberries at Syon House near London, while he was physician to Edward Seymour, Duke of Somerset, between 1547–52. Several ancient, layering mulberry trees survive there today, lending some support to this claim, and records exist of the purchase of Black Mulberries for Syon in 1604. The house was a requisitioned monastery dating back to the mid-15th century, so the present trees could even pre-date Turner’s time, although there is so far no evidence for this. Syon’s mulberries are possibly the oldest Black Mulberries in England, although a veteran tree in the village of Groton Winthrop (Suffolk) is claimed to have been planted around 1550.

The watershed for widespread planting and cultivation of M. nigra in Britain (probably alongside M. alba) came with King James VI & I’s 1607 edict calling on the landed gentry to plant mulberry trees in order to sustain an English silk industry based on home-grown, rather than imported, silk thread. James hoped to imitate successful sericulture ventures in Italy, Spain and France, where millions of (mostly White) mulberries had been planted in the 15th and 16th centuries (Coles 2019). When plantsman John Tradescant (1570–1638) purchased Black Mulberries in 1611 for the gardens at Hatfield House (UK), he travelled to nurseries in Leiden (Netherlands) and Paris) (Coles 2019). Mulberries purchased for Syon House in 1604 came from a nursery in Twickenham, while Loddiges nursery in Hackney (London) was the main source of mulberries planted in the 18th and 19th centuries (Coles in prep.).

James’s project soon petered out, leaving a legacy of isolated 400-year-old, mostly Black Mulberries in the grounds of some Jacobean and Tudor houses today, where they have been retained for their landscape value and inimitable fruit (M. alba, conversely, was probably grubbed out in most English locations). Examples of surviving early 17th century trees include those at Charlton House (London), and several Cambridge and Oxford Colleges (e.g. Christ’s College, Cambridge; Balliol and Merton Colleges, Oxford).

When James transferred his sericulture venture to the new colony of Virginia in the 1620s it was M. alba that was imported and planted en masse (Marsh 2020). Silkworms had found the leaves of the native red mulberry M. rubra unpalatable. Although M. nigra may have been planted at the same time as part of this early venture, it is not known if any trees have survived. Old black-fruited mulberries in North America are often M. alba. Some of the fruit from these varieties is very palatable and of similar appearance to that of M. nigra, but not so juicy, lacking its uniquely tart flavour, and having a longer stalk (making them easier to pick). M. nigra will not hybridize with native M. rubra and is therefore not a threat, unlike M. alba which has become an invasive alien species in North America.

Uses

All parts of Black Mulberry have medicinal properties, appearing in herbal pharmacopoeia over the past 2000 years; more recently its fruit has been dubbed a ‘superfood’ on account of its high levels of protein, fibre, vitamins and antioxidants (Razdan & Dennis Thomas 2021) but difficulties regarding mass production and storage have prevented it going mainstream. A syrup made from the fruit can be used as a gargle to sooth sore throats, as well as a mouthwash to treat ulcers. A tisane made from the leaves and root bark has been used as a vermicide. Fresh mulberries, which have a pleasant mix of tartness and sweetness, are used to flavour and colour sherbets, sorbets and meat dishes. A kind of molasses, known locally as pekmez, is commonly made from Black Mulberry fruit in the Caucasus (including present-day Turkey, Armenia, and Azerbaijan) (Coles 2019).

The timber of the Black Mulberry is valued by wood-turners and cabinet makers for the swirling grain patterns produced by its many burrs, which can be used for veneers. A number of small functional household items (treens) were made from wood salvaged from a Black Mulberry tree that grew in the garden of the English playwright, William Shakespeare, at New Place, Stratford-upon-Avon after it was felled in 1756 by the then owner who disliked visitors coming to see it (Bowe 2015) – though the clone survives in gardens as ‘Shakespeare’.

Cultivation

Pliny the Elder suggested Black Mulberry had been ‘neglected by the wit of man’ (Pliny 1945). He was referring to the almost complete lack of Black Mulberry varieties, despite millennia of cultivation, with differences essentially limited to the size of their fruit. Bean, too, commented that this is ‘a very unusual circumstance in a tree so long cultivated’ (Bean 1981). This phenomenon could be related to the species’ very large number (22) of duplicate sets of its 14 chromosomes (known as polyploidy), which may also be a factor in the occurrence of both dioecious and monoecious individuals – and even a capacity to change gender in maturity (Comai 2005).

Nevertheless it has long been popular for its fruits and latterly as a shade tree and an ornamental. Pliny the Younger wrote that he planted one in the garden of his villa in
Laurentum, near Rome, in the 1st century AD. Black Mulberry was also a tree of choice for the English landscape gardeners Fanny Wilkinson and Gertrude Jekyll in the late 19th and early 20th centuries (Coles 2019). In modern Britain the two most common M. nigra cultivars are ‘Chelsea’ (also known as ‘King James’) and ‘Shakespeare’. Neither differs meaningfully from the type; both were named because the original trees were of great age and had historic associations, but it is a moot point whether this merits the use of cultivar names. There is no comparable tradition, for example, of naming ancient yews or oaks, and were such a fashion initiated it would soon muddle the cultural histories of these great trees with a glut of unnecessary and unhelpful names. Those few M. nigra cultivars that are said to differ (marginally) in fruit size or flavour probably do so on account of environmental factors in their place of origin, and not because of any inheritable characteristic.

Bean (1981) was a fan of Black Mulberry, writing ‘It is not much planted now, but nothing gives to a garden fortunate enough to possess it a greater sense of old-world charm and dignity than a rugged old mulberry standing on a lawn’. This old-world charm can be achieved rather quickly in favourable conditions. Mulberries are difficult to age and can trip up the most august dendrologists: Alan Mitchell infamously fell victim to a Black Mulberry at East Bergholt Place in Suffolk, ‘which he estimated to be 300 years old. It had, in fact, been planted precisely sixty-four years earlier, on the day that the owner was born’ (Clarke 1988)! With this cautionary tale ringing in our ears, contemporary dendrologists would be well advised not to dwell too long on the subject of ageing mulberries in the absence of documentary evidence. Measuring them is rather easier, but consulting the records for M. nigra in databases such as monumentaltrees.com and the Tree Register do not betray any particular pattern; the tallest on record are approaching 15 m, the largest are over 5 m girth, but the ultimate stature of a tree will depend on local factors.


'Black Beauty'

Smaller than typical for the species, usually only to c. 5 m, with good-flavoured fruits (Hatch 2021–2022). Its origin is unclear.


'Black Persian'

Reportedly slightly more drought resistant than most clones, with large black fruits (Hatch 2021–2022).


'Charlton House'

Descended from a tree planted by order of James VI & I at Charlton House between 1608–1611 (as part of a sericulture plantation), where a single, gnarled black mulberry survives today. It was designated one of fifty ‘Great British Trees’ by the Tree Council in 2002 (moruslondinium.org). It isn’t clear whether material sold under this name represents the same clone, though it seems likely.


'Chelsea'

Synonyms / alternative names
Morus nigra 'King James'
Morus nigra 'King James I'

This cultivar’s selling point is its pedigree: the original tree was planted in what became the Chelsea Physic Garden, London, during the reign of King James VI & I (1566–1625). It had to be removed during the Second World War to make way for an air-raid shelter (romanticised accounts suggest it was damaged in a bombing raid; they also suggest King James himself had planted it). Cuttings were taken prior to its removal and the original tree’s descendants are now the most popular clone of Black Mulberry offered for sale in the UK (moruslondinium.org; Frank P Matthews 2022). Many nursery catalogues embellish this tree’s credentials, suggesting large fruit and early cropping, but such factors really depend on the environment where the tree is grown; in truth the use of a cultivar name is to preserve a tangible link to history.


'Jerusalem'

Propagated from a tree growing near the city of Jerusalem by Israeli nurseryman Omer Hochberg c. 2004. It was introduced to the UK by Hochberg’s friend, John Richards, who commissioned one hundred grafts, establishing the selection in cultivation where it remains commercially available (Andrews, Feltwell & Lane 2012). Both the leaves and fruits are reportedly larger than in typical forms (Edwards & Marshall 2019).


'Kaester'

Selected in Los Angeles in 1971 for its large, very sweet fruits produced in abundance (Hatch 2021–2022).


'Kokuso'

A Korean cultivar with fruits of average size, but very sweet, almost seedless and produced over a long season (Hatch 2021–2022). Several improved forms are known, all invoking some permutation of ‘Kokuso’ in their name.


'Noir of Spain'

Synonyms / alternative names
Morus nigra 'Everbearing'

A shrubby form of the species selected for its short, plump, superbly flavoured fruit. The leaves are particularly large (Hatch 2021–2022).


'Schatzenburg'

A name listed by Bolscher & van der Wurff (1998) with no further details as to its origin. It remains commercially available from several European nurseries.


'Shakespeare'

Another cultivar named for its pedigree; ‘Shakespeare’ is a descendant of a tree that grew in the garden of the playwright William Shakespeare in Stratford in the early 17th century, from which cuttings were taken in the 1750s when the tree was felled by the owner, who was annoyed by tourists coming to see it (Coles 2019).