Black mulberry (Morus nigra)

Black mulberry (Morus nigra) is a deciduous flowering tree native to southwestern Asia and the Iberian Peninsula. Black mulberry has been cultivated for a very long time in Europe and China for its edible fruit. It was imported into Britain in the 17th century with hope it would be useful in cultivating silkworms. However, silkworms prefer the white mulberry.

I. Appearance and Characteristics

Morus nigra, called black mulberry (not to be confused with the blackberries that are various species of Rubus), is a species of flowering plant in the family Moraceae that is native to southwestern Asia, where it has been cultivated for so long that its precise natural range is unknown.

Morus nigra is a deciduous tree growing to 12 metres (39 feet) tall by 15 m (49 ft) broad. The leaves are 10–20 centimetres (4–8 inches) long by 6–10 cm (2–4 in) broad – up to 23 cm (9 in) long on vigorous shoots, downy on the underside, the upper surface rough with very short, stiff hairs. Each cell has 308 chromosomes in total, and exhibits tetratetracontaploidy (44x), meaning that its genome contains seven chromosomes, and each cell has 44 copies of each.

The fruit is a compound cluster of several small drupes that are dark purple, almost black when ripe, and they are 2.5 cm (1 in) in diameter. Black mulberry is richly flavoured, similar to the red mulberry (Morus rubra) rather than the more insipid fruit of the white mulberry (Morus alba). Mulberry fruit color derives from anthocyanins.

Sometimes other mulberry species are confused with black mulberry, particularly black-fruited individuals of the white mulberry. Black mulberry may be distinguished from the other species by the uniformly hairy lower surface of its leaves.

II. How to Grow and Care

Sunlight

Black mulberry thrives in conditions where it can receive full sunlight, which is crucial for optimal growth and fruit production. The intensity of the light should be high, with the plant benefiting from long durations of direct exposure. However, black mulberry also exhibits a tolerance for partially shaded environments, though this may result in reduced vigor and lesser fruit yield. To capitalize on its light adaptability, black mulberry should be positioned outdoors where it receives unfiltered sunlight for the majority of the day. While it can endure some shade, especially during the hottest parts of the year, consistent full sun is key for its health and productivity.

Watering

Black mulberry thrives in a well-hydrated environment, indicative of its origins where it benefits from consistent moisture. It exhibits a preference for regular watering, aligning with its need for a stable water supply to support its growth. For optimal health, black mulberry should be watered once every two weeks. As an outdoor plant that often graces gardens, black mulberry’s ability to adapt to various climate zones makes it a versatile choice for gardeners looking to add both foliage and fruit interest while considering regional water availability.

Fertilizing

To augment growth and fruiting, fertilize black mulberry in early spring with balanced nutrition fertilizer, specifically a granular, all-purpose blend. Apply monthly during the growing season, abiding by the manufacturer’s suggested amount, which typically ranges around 1-2 cups per plant, depending on size. Cease fertilization in late summer to prepare black mulberry for dormancy. Fertilizing black mulberry is crucial for bolstering root strength, foliage density, and optimizing berry yield.

Critical: avoid over-fertilization to prevent root burn and excessive vegetative growth at the expense of fruit production. As growth phases shift, adjust fertilizer concentration accordingly. Usage of gloves and ensuring even distribution can enhance fertilizer efficiency and safety.

Pruning

Pruning is crucial for maintaining health and promoting fruit production; annual pruning of dead or overcrowded branches helps prevent disease spread and encourages good air circulation.

Propagation

Black mulberry thrives best when propagated through cuttings. Gardeners should select healthy, disease-free stems for the best chance of rooting success. The cuttings, ideally semi-ripe and with several leaf nodes, can be planted in well-drained soil mixed with rooting hormone to

encourage development. Providing consistent moisture and warmth will help to establish strong roots, and once rooted, black mulberry can be transplanted to its final location where it will mature into a fruit-bearing tree.

Transplanting

The optimal time to transplant black mulberry is during late spring to early summer, as the mild weather supports root establishment. Choose a sunny location with well-draining soil. Ensure the spot accommodates black mulberry’s mature size to avoid future stress.

III. Uses and Benefits

The fruit is edible and the tree has long been cultivated for this property. Both the tree and the fruit are known by the Persian-derived names toot (mulberry) or shahtoot (شاه توت) (king’s or “superior” mulberry), or, in Arabic, as shajarat tukki. Often, jams and sherbets are made from the fruit in this region.

The fruit has been present in the Southern Levant since antiquity. In the Books of Maccabees, it is noted that the Greeks used the fruit to provoke their war elephants in preparation for battle against Jewish rebels during the Maccabean Revolt in the 2nd century BCE. The fruit is also mentioned in the Mishnah and later rabbinic texts. In the 9th century CE, Al-Kindi referenced the fruit as having healing seeds, while Ibn Badis, writing in the 11th century, noted its use in the production of ink.

In Europe, the largest-documented local concentration of black mulberries may be found in the vineyards of Pukanec in Slovakia, which contain 470 black mulberry trees.

The black mulberry was imported into Britain in the 17th century in the hope that it would be useful in the cultivation of silkworms (Bombyx mori). It was unsuccessful in that enterprise because silkworms prefer the white mulberry. However, the plantings have left a legacy of large and old trees in many country house gardens and it was listed in the Award of Garden Merit of the Royal Horticultural Society until 2013. It was much used in folk medicine, especially in the treatment of ringworm.