25th October 2018
Morus Londinium’s Peter Coles finds all the main species of mulberry at Kew – Black, White, Red… and even the Paper Mulberry … which isn’t strictly a mulberry.
Morus Londinium’s ongoing survey of UK mulberry trees– with over 550 entries to date and still growing – has shown that there’s probably a Black Mulberry (Morus nigra) not far from you – at least if you live in Greater London. Some of the trees are over 200 years old and a few may even date from the 17th century. If you want to find a White Mulberry (Morus alba), it’s quite a lot harder. There are several in London, but they tend to be under 30 years old and are often bunched together – such as those in Kensington Palace Gardens or the ones planted for the millennium around the Dreadnought Building of Greenwich University. Finding a Paper Mulberry (Broussonetia papyrifera) is even harder, although there are a few planted as street trees in Hackney (e.g. Kynaston Road). But if you want to find a Red Mulberry (Morus rubra) you’ll be very hard pushed.
Fortunately, the incomparable Royal Botanical Gardens, Kew has examples of each species in at least early maturity. It took me a while to find them when I went there recently, but if you enter by Victoria Gate, most of the trees are more or less straight ahead (i.e. walk north west).
The oldest of Kew’s Morus (mulberry) specimens is a black mulberry, just beyond an information post on the way to Pagoda Walk from Victoria Gate. There is an unsubstantiated claim (see Maud Grieve's A New Herball) that the tree was grown from a slip taken from Shakespeare's mulberry tree in Straford-upon-Avon, But the Bard's tree was felled by its cantacerous new owner, the Rev. Francis Gastrell, around 1756, while the gardens at Kew only began to be laid out in earnest a few years later, after 1759. It is possible that slips from the felled Shakespeare tree were taken and grown on somewhere else, of course.
Pliny the Elder described Morus nigra as having been ‘neglected by the wit of man’, as there are hardly any significantly different cultivars or varieties. Black Mulberry varieties differ essentially only n the size and shape of their fruit, which ripens here in July and August. For many, this brief summer window of opportunity for foraging fresh black mulberries is eagerly awaited, even if it is a messy business.
Kew’s venerable Black Mulberry leans over at an angle, as is typical of the species. A more upright specimen can be found near to the tree-top walk. The leaves on old wood are heart-shaped and rough to the touch. On new shoots they can be very different shapes, though – even on the same branch – with indentations more like those found on M. alba leaves. Contrary to popular belief, silkworms will feed happily on the young leaves of M. nigra, albeit producing a coarser silk than when they are fed onM. alba leaves.
Kew has several White Mulberries, representing a few of the dozens of taxa. There are a couple of young M. alba beside the Minka House and Bamboo Garden.
Nearer to Victoria Gate, a mulberry grove features a very nice example of Morus cathayana (alongside Morus rubra, Morus nigra, Broussonetia papyriferaand B. kazinoki).
When I visited in early October, the ground beneath the trees was carpeted with purple crocuses. M. cathayana is native to China and is considered a distinct species, though closely related to M. alba. Its leaves are not so glossy as M. alba and are almost felt-like to the touch.
The real trump card in Kew’s mulberry collection is its Morus rubra, or Red Mulberry. A native of the eastern and central United States, where it grows in deciduous lowland forests and can reach a great height, the species has never taken to the British climate. The American naturalist, William Bartram, found them growing wild on his treks through Georgia and the Carolinas in the late 18th century. As the British botanist William Jackson Bean (curator of Kew in the early 1920s) noted: ‘In my experience [the red] mulberry thrives the worst of those here mentioned. At Kew it always has an unhappy appearance, and I do not know of good trees elsewhere.’ It doesn't look too unhappy to me, and I was certainly happy to find it.
When James I tried to start a silk industry in his new colony of Virginia in the early 1600s, having failed at home, the first efforts used the native M. rubra leaves to feed the silkworms. But this soon proved unsuccessful - the leaves are too tough for hatchling silkworms – and white mulberries were imported and cultivated, eventually forcing the native red mulberry onto the endangered species list.
The Paper Mulberry is no longer classified as a mulberry (its Latin name was once Morus papyrifera), although it is a member of the Moraceae genus (like the fig, whose leaves it resembles in shape).
It has rough, often concave leaves and very distinctive red fruit, which were visible on Kew’s tree when I visited in early October. They look more like flowers than fruit and are 'drupes'. They are sweet to the taste.
The Paper Mulberry is most celebrated for a bast made from its bark. This is pounded and used to make paper, including the first paper money – invented in China – and a kind of cloth known as tapa, notably in the Pacific Islands. Next to the B. papyriferais stands the closely related Broussonetia kazinoki, native to China, Japan and Korea.