General: Mulberry family (Moreaceae). White mulberry is an introduced, small to medium sized shrub or tree. The leaves are alternate, simple, serrate or dentate, ovate to broad ovate, and two to seven inches long (Dirr 1990). The flowers are small, greenish, crowded in clusters, and hanging in catkins. The fruit is blackberry like, typically white but sometimes pinkish violet, insipid and so plentiful it litters lawns and pavements (Taylor 1965). The bark is light brown to gray and smooth, becoming divided into narrow scaly ridges.
Distribution: Morus alba is a Chinese tree, cultivated throughout the world wherever silkworms are raised. It is occasionally cultivated in Japan, Europe, North America, and Africa. In Michigan, white mulberry is frequent in urban environments in the southern half of the Lower Peninsula, occasionally in the northern half of the Lower Peninsula and the Upper Peninsula (Barnes & Wagner 1981). This species is naturalized in the urban environment and rare in disturbed forest communities (Ibid.). For current distribution, please consult the Plant profile page for this species on the PLANTS Web site.
White Mulberry is a common tree that has been found throughout Illinois (see Distribution Map); it probably occurs in every county. This tree is especially abundant in urban areas. It was introduced from Asia as a food plant for the Chinese Silkworm (Bombyx mori) during the 19th century. Habitats include disturbed open woodlands, savannas and thickets, woodland borders, fence rows, powerline clearances in wooded areas, river banks, vacant lots, and unmowed waste areas. Sometimes White Mulberry is cultivated as a landscape tree, although this is less common than in the past.
Shrubs or trees, 3-10 m tall. Bark gray, shallowly furrowed. Branches finely hairy. Winter buds reddish brown, ovoid, finely hairy. Stipules lanceolate, 2-3.5 cm, densely covered with short pubescence. Petiole 1.5-5.5 cm, pubescent; leaf blade ovate to broadly ovate, irregularly lobed, 5-30 × 5-12 cm, abaxially sparsely pubescent along midvein or in tufts in axil of midvein and primary lateral veins, adaxially bright green and glabrous, base rounded to ± cordate, margin coarsely serrate to crenate, apex acute, acuminate, or obtuse. Male catkins pendulous, 2-3.5 cm, densely white hairy. Female catkins 1-2 cm, pubescent; peduncle 5-10 mm, pubescent. Male flowers: calyx lobes pale green, broadly elliptic; filaments inflexed in bud; anthers 2-loculed, globose to reniform. Female flowers: sessile; calyx lobes ovoid, ± compressed, with marginal hairs; ovary sessile, ovoid; style absent; stigmas with mastoidlike protuberance, branches divergent, papillose. Syncarp red when immature, blackish purple, purple, or greenish white when mature, ovoid, ellipsoid, or cylindric, 1-2.5 cm. Fl. Apr-May, fr. May-Aug.
Greenhouse experiments show variable germination rates, with germination generally improving with cold stratification (, review by ), and variable results after ingestion by wildlife [12,85]. Wild-collected white mulberry seeds showed high germination rates (92.3%) in greenhouse trials where seeds were exposed to indirect sunlight and fluctuating temperatures from June to October. Germination rates were lower (78.3%) for seeds that had been ingested by box turtles prior to germination trials . Another study found that dormancy of white mulberry seeds varies; seeds from the same cohort may exhibit seed coat dormancy, embryonic dormancy, or both. Seeds exhibiting all 3 types of dormancy showed improved germination following both cold stratification and digestion by American robins. Seeds had germination rates of 45.8% when just digested by American robins and 68.8% when digestion by American robins was combined with 90-day cold stratification. In contrast, control seeds with no treatment had a germination rate of 34.0% while those only exposed to cold stratification had a germination rate of 55.2%. Scarification of control seeds with a 15-minute sulfuric acid treatment reduced germination rates .
A forestry handbook from India reports that white mulberry seeds take 35 days to germinate , though one review reports an expected germination rate of 73% to 84% 8 to 12 days following 60-day stratification in sand .
The scientific name of white mulberry is Morus alba L. (Moraceae) [44,72]. In North America, white mulberry hybridizes with the native red mulberry (M. rubra) ([18,153,171,174], review by ). Both species are highly variable and frequently confused with each other . Numerous white mulberry cultivars occur in North America ([11,32,41], review by ).
Shrubs or trees , to 15 m. Bark brown tinged with red or yellow, thin, shallowly furrowed, with long, narrow ridges. Branchlets orange-brown or dark green with reddish cast, pubescent or occasionally glabrous; lenticels reddish brown, elliptic, prominent. Buds ovoid, 4-6 mm, apex acute to rounded; outer scales yellow-brown with dark margins, glabrous or with a few marginal trichomes; leaf scars half round, bundle scars numerous, in circle. Leaves: stipules ovate to lanceolate, 5-9 mm, pubescent; petiole 2.5-5 cm, short-pubescent. Leaf blade ovate, often deeply and irregularly lobed, (6-)8-10 × 3-6 cm, base cuneate, truncate, or cordate, margins coarsely serrate to crenate, apex acute to short-acuminate; surfaces abaxially glabrous or sparingly pubescent along major veins or in tufts in axils of principal lateral veins and midribs, adaxially glabrous to sparsely pubescent. Catkins: peduncle and axis pubescent; staminate catkins 2.5-4 cm; pistillate catkins 5-8 mm. Flowers: staminate and pistillate on same or different plants. Staminate flowers: sepals distinct, green with red tip, ca. 1.5 mm, pubescent; filaments ca. 2.7 mm. Pistillate flowers: ovary green, ovoid, slightly compressed, ca. 2 mm, glabrous; style branches divergent, red-brown, 0.5-1 mm; stigma papillose. Syncarps red when immature, becoming black, purple, or nearly white, cylindric, 1.5-2.5 × 1 cm; achenes light brown, ovoid, 2-3 mm.
A forestry handbook from India lists white mulberry seeds as viable for 720 days . Tests at a nursery in Nebraska found that, while white mulberry seeds remained viable for at least a year when stored in cool, sealed conditions, they deteriorated rapidly upon removal from storage .
White mulberry seeds have been found in soil samples even when mature plants are not present in extant vegetation, though the seeds were not always viable. White mulberry was absent from aboveground vegetation but present at low density in the soil seed bank in deciduous forests in Bronx, New York, with viable seeds occurring at a soil depth of 0 to 4 inches (0-10 cm) . White mulberry seeds were detected in 32% of soil samples taken from a woodlot in southern Ontario in November, occurring in samples at a density of 334.8 seeds/m². These seeds were not viable in seedling emergence trials . In west-central Iowa, white mulberry seeds were present in the seed bank in coniferous woodland, deciduous shrub, tallgrass prairie, and midgrass prairie plant communities. Neither the viability of these seeds nor white mulberry's presence in the aboveground vegetation were reported . In southeastern Arizona, white mulberry was found in the soil seed bank of a riparian deciduous forest but was not found in extant vegetation .
Introduced into the U.S. and it is considered invasive by several sources. Please consult the Plants Web site and your State Department of Natural Resources for this plant’s current status, such as, state noxious status and wetland indicator values.