Aliens in the Backyard: Plant and Animal Imports into America

A Sow’s Ear from a Silk Purse: The Legacy of Sericulture

29 A Sow’s Ear from a Silk Purse The Legacy of Sericulture Despite four hundred years of effort, the American silk industry has never achieved the success its boosters dreamed it might. But efforts to establish it have introduced alien flora and fauna. Ironically, the species that silk boosters worked hardest to establish have thrived least, while less popular species and escapees have become the objects of massive government-sponsored eradication programs; programs that have, in turn, had untoward effects upon the native American landscape. The Chinese are generally credited with inventing silk culture. Chinese legend tells of an emperor’s wife who first taught people how to rear the silkworm (Bombyx mori) on the leaves of the white mulberry (Morus alba). As silk was enormously profitable, the Chinese jealously guarded the secrets of its manufacture, and Westerners, confusing silk with cotton, supposed it grew on trees. Two intrepid sixth-century Nestorian monks used a hollow cane to smuggle the first silkworm eggs out of China to Constantinople. From these few egg clusters descended the millions of silkworms that would be raised in Europe over the next twelve hundred years. Europeans did not know of the white mulberry , however, until the fourteenth century, contenting themselves with raising worms on the black mulberry, M. nigra, an acceptable but inferior food source for Bombyx.1 Cold and humid British winters prevented the English from establishing profitable silkworm farms. That eastern North America’s winters are far colder did not deter Virginia’s colonists when they discovered mulberries in the woods around Jamestown. “There was an assay made to make silke, and surely the wormes prospered excellently well until the master workman fell sick, during which tyme they were eaten with ratts.”2 Despite this inauspicious beginning, silk would remain an American get-rich-quick dream for the next three hundred years. King James I encouraged silk farming not only to promote luxury goods, but also to undermine Virginia’s love affair with tobacco. So intent was 30 Aliens in the Backyard he to stop cultivation of the noxious sotweed that he required new plantations to plant mulberries. Georgia’s promoters so favored silk that Savannah’s coat of arms to this day carries a silkworm on its crest. Benjamin Franklin urged the establishment of a silk factory in Philadelphia. And both George Washington and Thomas Jefferson planted mulberries on their plantations. At first boosters hoped that the American or red mulberry, Morus rubra, would prove useful. Native to much of eastern North America from New England south to Florida and west to Iowa and Texas, the red mulberry promised free food for the taking. Native Americans had long cultivated the tree in groves near their villages, harvesting the fruit to eat and using the fibrous inner bark to make garments. Indeed, the remnants of De Soto’s ill-fated sixteenthcentury expedition, taking their cue from Choctaw squaws, included ropes made from this bark and used to rig the vessels they built to travel back to Mexico. But Bombyx silkworms, although they will eat red mulberry leaves, do not like it, preferring those of their natural food tree, the white mulberry.3 In 1522 Cortez imported both Bombyx worms and M. alba to Mexico, making him perhaps the first person to introduce sericulture to the New World. English colonies in North America established groves of white mulberry following Jamestown’s founding nearly a hundred years after Cortez. Hopeful farmers also planted the black mulberry, M. nigra, but it proved too tender to survive New England winters. Farther south, though, escapees of both white and black mulberries naturalized. The white became rather common in the eastern United States, while the more tender black mulberry remained restricted to the warmer south. Today the white mulberry grows throughout the continental United States and Hawaii, outcompeting and hybridizing with the native red mulberry, which is actually in decline in some areas. Although watchdog groups classify the tree as moderately invasive, many consider it a weed. Nevertheless , it is still commercially available. The year 1776 replaced English speculators with American, and the boondoggle continued. Like all things American, it also grew in scope, setting the stage for the 1830s “mulberry mania.” William Robert Prince was the fourth generation to run the family’s nursery in Flushing, Long Island. A restless entrepreneur , Prince introduced osiers, sorghum, the Chinese yam, and merino sheep into the United States. He also helped found Sacramento, California, on a gold-prospecting...