Botany
Weed of the Month
April, 2010: Broussonetia papyrifera, paper mulberry
Broussonetia papyrifera, paper mulberry
Photograph courtesy of Patricia Howell, Atlas of Florida Vascular Plants
Distinguishing Characteristics: This is a fast-growing, low-branching, bushy tree, occasionally reaching 50 feet in Florida. Like most plants in the Mulberry family, all parts exude a milky sap when damaged. The young twigs are conspicuously pubescent, with coarse, reddish, spreading hairs. Leaves are deciduous and alternate, or sometimes opposite as well, and generally ovate in shape, either unlobed, or variously and deeply lobed, particularly on vigorous growth. They have an uneven, broadly rounded or shallowly cordate base, an acuminate apex and a sharply serrate margin; the underside is densely pubescent with whitish or grayish hairs, especially when the leaves are young, and the upperside is roughened with stiff, forward-pointing hairs. Foliage texture is coarse, with leaves often as much as eight inches long and five inches wide. The greenish flowers are borne with the emerging leaves, the males in drooping catkins 2 - 4 inches long, and the females, on separate trees, in globose heads almost an inch in diameter. The female flowers mature into club-shaped, red-orange, sweet, fleshy fruits aggregated into spiky balls.
Broussonetia papyrifera, paper mulberry
Photograph courtesy of John Kunzer, Atlas of Florida Vascular Plants
Distribution: The paper mulberry is native to eastern Asia, but it has become widely naturalized, particularly in parts of southern Asia and in Latin America, and is occasionally invasive. It is widespread in the eastern half of the United States, from Massachusetts to Kansas, south to Texas and Florida, as well as in Hawaii. In the northern states, it is often killed to the ground during the winter.
Occurrence in Florida: This species is common along roadsides and in disturbed woodlands, mostly in the northern and central peninsula, with a few stations in the Panhandle and in South Florida.
Broussonetia papyrifera, paper mulberry fruit
Photo courtesy of Will Cook
Similar Species in Florida: The paper mulberry could easily be confused with our native Morus rubra, the red mulberry. The plants can be distinguished by the following characters. The red mulberry has leaves that are deeply cordate at the base and inconspicuously pubescent beneath; while the leaves of the paper mulberry are usually broadly rounded or shallowly cordate at the base, and conspicuously whitish or grayish pubescent beneath, at least when young. In addition, the twigs of the red mulberry are glabrous, or pubescent with a soft, fine fuzz, and the fruit clusters are deep red and elongate; while the paper mulberry has twigs pubescent with coarse, reddish, spreading hairs, and the fruit clusters are bright red-orange and globose.
Broussonetia papyrifera, paper mulberry
Photo courtesy of Will Cook
Means of Dispersal: Broussonetia produces suckers from the roots and often makes dense thickets. The brightly colored, fleshy fruits are attractive to birds which spread the seeds far from the parent plant. The seeds germinate readily a month or so after ripening.
Comments: This plant has been cultivated for millennia, particularly for its bark which was used to produce a high quality paper by both the Japanese and the Chinese, and a cloth known as tapa by the Polynesians. The leaves are occasionally used as a food for silkworms, and the sweet, fleshy fruits are also occasionally used as food for humans. These fruits are, however, a rarity in most parts of the world outside the natural range of the plant. Either by chance or accident, all of the trees introduced into the Pacific islands are male. And in Florida, either most of the plants are males, or the female plants do not often produce fruits. Yet enough seeds are set to allow the plant to become an invasive pest, and it is listed as a Category II Invasive by the FLEPPC. It is a conspicuous element of the vegetation of northern and central Florida, especially in the fall when its foliage takes on a sickly yellow color.
Further Information: Langeland, K.L., H.M. Cherry, C.M. McCormick and K.A. Craddock Burks. 2008. Nonnative plants in Florida’s natural areas. IFAS Communication Services, University of Florida, Gainesville. 193 pp.; http://en.wikipedia.org/wiki/Paper_Mulberry
Dr. Richard Weaver, Botanist
Florida Department of Agriculture and Consumer Services
Division of Plant Industry
1911 SW 34 Street
Gainesville, FL 32614
