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Morus alba

White mulberry

White mulberry (Eng), morera, morera blanca (Spa), morera blanca, morer blanc (Cat), masustabe, marhugatze (Baq), moreira branca (Glg), amoreira-branca (Por).

Non-native

“Kublai Khan commanded the minting of money from the membrane found between the bark and trunk of the mulberry.”

‘The travels of’ Marco Polo

DESCRIPTION

A branching tree up to 18 m tall, with smooth grey bark when it is young, but which becomes thick, very cracked and brown or grey with age. The leaves are deciduous, simple, alternate, 3 to 22 cm long and somewhat narrower than they are wide. They are very variable in shape: oval, rounded or lobed, with two or more lobes, always with a toothed margin and long, somewhat hairy leaf stalks where you can see latex when they are broken. They are thin, usually finishing in a tip, heart-shaped at the base and commonly hairless. On the upper side they are shiny, and the underside may have a few hairs between the nerves. These features, together with long-stalked fruits, which when ripe are rather bland, and usually white, white-greenish or pinkish in colour (although they are occasionally red or black), differentiate this species from the related Morus nigra. The flowers are not very showy and are unisexual, i.e., they are divided into male and female. They are usually found on different plants, but sometimes they are separated on the same tree. The fruit should really be called an infructescence, because it is complex and each small ball is the true fruit. These group together to form a structure similar to a blackberry that is known in botany as a sorosis. The white mulberry, however, is completely different, because the blackberry is in the rose family (genus Rubus).

ECOLOGY

Mulberry trees are indifferent to soil type, though they grow best on deep, fertile substrates and less well on highly acidic ones. This species is very tolerant of pollution, severe pruning, and the rigors of cold and heat, provided that there is not a prolonged lack of water.

DISTRIBUTION

This is an oriental plant and is very difficult to pin down its exact natural range as it has been cultivated since ancient times and its seeds are easily transported by birds. It is believed to be native to central and eastern Asia: China, Korea, Mongolia, and northern India. However, it is not certain whether in Japan it is native, or an ancient introduction. It was introduced to the Mediterranean basin in the 6th century, brought to Constantinople by monks, for silkworm-breeding. Legend has it that the fruits arrived hidden in a few sticks of bamboo, because the Chinese kept the lucrative business of silk top secret.

On the Iberian Peninsula and the Balearic Islands it is frequently cultivated as an ornamental, mainly in the east, centre and south, and it was particularly important in Murcia and Granada, where it was grown for the production of silk. German geographer and traveller, Alexander von Humboldt, speaks of this species in his Journal in Spain: “Even before Murcia, I had come across a great number of mulberry trees. From time to time you can find the small boxes where the worms are kept. […] The mulberry trees here in Granada are called 'morales'”. This species has naturalized in many places, particularly in ditches, uncultivated fields and the vicinity of human settlements.