Mulberry, Morus

According to Romeyn Beck Hough’s 1907 Handbook of the Trees of the Northern States and Canada East of the Rocky Mountains, “The White Mulberry, in that its leaves furnish the most valuable food known for the silkworm, has the distinction of being the tree about which more has been written than any other tree. Upon its existence, too, depend the employment of vastly more people and capital than any other tree, and no other tree has been so extensively cultivated”.

Ironically, mulberry (Morus) trees are seen as trash trees now, at least in the U.S. Red Mulberry (Morus) is native to Ohio, but White Mulberry (Morus alba) from Asia is more aggressive and is the one most often seen today, especially in urban areas. 

Mulberry features

Like most trees found in Ohio, mulberry leaves and branches are arranged alternately. Branches and leaves, and in the winter, leaf scars, are not directly across from each other, but instead alternate left, right, left, right, along the length of a twig, like human footprints on a trail. In general, the leaves appear to be pinnately-veined, which is to say, that there is a single primary vein, with secondary veins attached at different points along its length. Palmately-veined leaves have multiple veins attached at the base. But at the base of each mulberry leaf are two lateral veins with secondary veins attached pinnately along their length. 

Leaves

What sets mulberries apart from most other trees is that they have multiple leaf shapes. A few other Ohio trees have multiple leaf shapes, such as Sassafras, whose leaves have four different shapes. But mulberry leaves, especially White Mulberry have lots of shapes, with some having no lobes, some having three, some having several lobes on one side of the central vein, and none on the other, and so forth. The leaves on younger shoots typically have more lobes.

Mulberry leaves typically have prominent teeth. The leaves are from 2 to 7 inches long, with Red Mulberry leaves, on average, larger than White Mulberry leaves. Red Mulberry leaves have dull top surfaces, and White Mulberry leaves are shinier. The differences in leaves are subtle, and because mulberries hybridize, pure Red Mulberry trees might one day be extinct. Mulberry leaves turn yellow in autumn. 

Fruit

Mulberry flowers appear as small yellow-green catkins. Mulberries are usually dioecious, having male and female flowers on separate trees, but they can be monoecious as well, and have both flowers on the same tree. The familiar fruits resemble blackberries, but they are not closely related. Each mulberry fruit is actually a collection of numerous small fruits, as is also true of strawberries, and of mulberries’ relative, the Hedge Apple (aka Osage Orange, Maclura ). Blackberries and raspberries are single fruits, each one emerging from a single flower.

The difference between Red, White, and Black Mulberries is not the color of their fruits, but of their buds in spring. All of their fruits turn reddish-black when ripe. M. nigra and our native M.  have superior fruit to M. alba. White Mulberry fruits grow in clusters, while Red Mulberry fruits are solitary. But mulberries can hybridize, so they might not be all of one or the other. Notice that white, unripe berries are poisonous. 

Bark

Mulberry trees can be recognized in winter by their bark and trunk characteristics. Mulberries sprout aggressively, often resulting in horizontal ridges on the trunk where shoots once emerged. Juvenile bark has a distinct orange color, and prominent lenticels, which are pores that apparently allow gases to move into or out of the trunk. The bark of mature trees is furrowed with a zig-zag pattern, with orange color often visible in the grooves. Mulberries also often feature purple sap oozing from wounds. (Numerous sources describe mulberries as having toxic white sap in the leaves and twigs. Presumably, the dark color is the result of oxidation). One other common trait characteristic of Mulberry is orange roots, also seen in its relative, Hedge Apple. 

Shape

And finally, mulberry trees have a somewhat distinctive shape, in that they often spread horizontally, with the branches bowing downward toward the ground. They also sometimes show numerous clusters of growth at the twig intersections. These are described as “witches’ brooms”, much like those associated with Hackberry (Celtis ). 

Mature Red Mulberry trees typically have a height of 60 feet and a trunk diameter of approximately 2.0 feet. White Mulberries are somewhat smaller. Ohio’s Champion Red Mulberry, located in Ross County, has a height of 54 feet, a trunk diameter of 4.5 feet, and a crown width of 78 feet. Monumental Trees reports a specimen in Kansas with a girth of 20.3 feet! According to the Columbus Street Tree Inventory, White Mulberry is the City’s 34th most common tree, putting it ahead of Black Walnut, Eastern White Pine, and Northern Catalpa. 

ID Summary

Mulberry trees usually have some leaves that are irregularly lobed, with teeth. The trunk often shows orange coloring and horizontal ridges from which shoots emerged. Dark, purple to black stains are often present below injuries. Raspberry-like fruits may be present in summer. 

Similar Trees

Mulberries resemble Sassafras in having irregularly-lobed leaves, but Sassafras leaves have only 4 shapes, while mulberries often have many, and only mulberry leaves have teeth. Sassafras typically have alternately-arranged green twigs. Unlobed mulberry leaves resemble Basswood, but Mulberry twigs have white sap. 

Mulberry trees like moist soil, but Red Mulberry prefers heavy shade, while White Mulberry prefers open sun. Consequently, Red Mulberries are most common in wooded areas, while White Mulberries are found in city-scapes. Red Mulberries are limited to the eastern U.S. (and Canada), but the more adaptable, and aggressive White Mulberries can be found in nearly every state. Lucy Braun’s Woody Plants of Ohio indicates that Red Mulberry is present in most of Ohio’s counties, but absent in several of the north central ones. 

Uses

Mulberry lumber has a Janka hardness of 1,680 lbf and a density of 0.69 g/cc, according to the Wood Database, compared to the median of my list of 73 Ohio trees of 1,075 lbf and 0.64 g/cc. Red Mulberry has good working properties and has a pleasant, orange color, but due to its scattered distribution and small size, it has little commercial value. Red Mulberry resists decay, and was widely used for fence posts. Its durability also made mulberry wood useful for small parts of wooden ships, including “tree nails”, or dowels. Historically, Red Mulberry wood was also favored for making caskets. The USDA Plants Database indicates that, “White Mulberry wood is valued for sporting goods due to its durability, flexibility, and elasticity. It is used mainly for tennis and badminton rackets, hockey sticks, furniture, agricultural implements, and house and boat building materials.” 

Mulberries have been cultivated for thousands of years because of their association with silk. Mulberry leaves, usually White Mulberry, were harvested several times per year and fed to silkworms (Bombyx mori). The leaves were often made more accessible by the practice of pollarding, which consisted of cutting the trees to a height of 3 or 4 feet and harvesting the shoots. Some claim that White Mulberry pollards still line the roads in southern France.

According to the website Edible Wild Food, in 1624 the legislature of Virginia required every male resident to plant at least four white mulberry trees to promote a North American silk industry. Initially, the Settlers fed the silkworms local Red Mulberry leaves, but the silkworms apparently didn’t like them. White Mulberry trees were then imported, with only slightly more success, leaving us with no silk industry, but countless White Mulberry trees. White Mulberries are also pollarded for use as cattle fodder. According to Noel Kingsbury’s Hidden Histories, Trees, “Mulberry foliage is not favored only by silkworms; the leaves are equally good for feeding livestock. their use as cattle fodder is growing across the world, especially the warmer climates the tree prefers”. 

Mulberry fruits are eaten whole, and used to make pies, jellies and jams, wines, and aperitifs. However, they have a short shelf life and are generally unavailable in fresh form. Red and Black Mulberries have the best fruit, while White Mulberry fruits are often described as “insipid”. In the interest of avoiding artificial coloring, mulberry fruits have been used as a source of red color in food. 

Mulberry trees are sometimes used in landscaping, but some cities ban their planting because of the extreme allergic reaction many people have to their pollen. In fact, usually only males produce pollen, but the females are disliked for their fruit, which seldom goes to use in this country, and which causes purple stains, often dropped by birds. The iNaturalist website states that, “The white mulberry is scientifically notable for the rapid plant movement involved in pollen release from its catkins. The stamens act as catapults, releasing stored elastic energy in just 25 µs. The resulting movement is approximately 350 miles per hour (560 km/h), over half the speed of sound, making it the fastest known movement in the plant kingdom.”

According to the Native American Ethnobotany Database, many or most of the Natives used Red Mulberry for food, but infusions made from root bark were also used for medicinal purposes, including:

• Urinary aid,
• Anthelmintic (worm removal),
• Antidiarrheal,
• Purgative,
• Stimulant,
• Panacea,
• Emetic (to induce vomiting).

The Natives also used mulberry wood to make bows, as is true of the related Hedge Apple.

Mulberry leaves, bark, roots, berries, and sap are used in traditional Chinese medicine. The toxic sap blocks the metabolism of sugars in many animals, but this property leads to its potential use for treating diabetes. 

According to A History of Packaging, Paula Hook and Joe E. Heimlich, “Sheets of treated mulberry bark were used by the Chinese to wrap foods as early as the first or second century B.C.” The Paper Mulberry (Morus papyrifera), native to Asia, was used to make bark cloth. 

Numerous varieties of birds and mammals feast on mulberry fruits. Deer and rabbits consume the leaves, and beavers consume mulberry bark. 

The ancient Roman poet Ovid relates a story in which the lovers Pyramus and Thisbe, from rival families, agreed to meet beneath a mulberry tree. But Thisbe encountered a lioness, and dropped her cloak as she fled. Pyramus found the cloak, and believing that Thisbe had been killed, committed suicide, followed by Thisbe’s suicide when she found him dead. The gods changed mulberry fruits to red to honor their love. The story has been retold many times, including Shakespeare’s Romeo and Juliet, and more recently, the Broadway play and movie, West Side Story. Unfortunately, in the recent versions, the mulberry tree was written out of the story. 

According to Fred Hageneder’s The Meaning of Trees; Botany, History, Healing, Lore, in some Chinese traditions, k’ong-sang, the World Tree at the center of the universe is a mulberry. The tree is hermaphroditic, because it dates back to before the separation of yin and yang, male and female. 

Mulberry trees have little commercial value in the West today, and people curse their pollen and staining fruits. But for nearly 2,000 years, mulberry trees fueled trade on the Silk Road, connecting China to Egypt, Greece, and Rome. The road was a conduit for the exchange of not just goods, but art, music, mathematics, science, philosophy, religion – and genes. Our history and culture would look very different without the mulberry.