(Cox 1945, Spongberg 1990). Among the species they introduced into the U.S. horticultural trade are some notorious plant invaders. George Rogers Hall collected Lonicera japonica (Japanese honeysuckle) (Spongberg 1990). Thomas Hogg reputedly introduced Pueraria lobata (kudzu) (Spongberg 1990), the scourge of disturbed land in the southeastern United States (Westbrooks 1998). Even if Hogg was the first purveyor of kudzu, he probably was not the last; it was available directly from Japan in the 1890s and also appears among the accession records of the U.S. Plant Introduction Service (Mack 1991).
The attractions that drew 19th century plant collectors to China remain: a diverse flora in a variety of environments that are similar to large swaths of North America and western Europe (Qian and Ricklefs 1999). In a sense, the work of the early collectors was interrupted. As China became increasingly unstable politically early in the 20th century, western plant collectors suspended their operations (Spongberg 1990, Mack 2001). As a result, there was little or no exportation of horticultural species or plant collecting by westerners until recently (Valder 1999). Collections of crop species, such as soybean, however, have been extensive in recent years.
Resumption of large-scale sustained trade with the West means that Chinese horticultural material can and will once again be exported in quantity. Seventy-five years of little or no opportunity for plant exportation from mainland China by western horticulturists has created much pent-up enthusiasm for new horticultural species from the temperate world’s last great unexplored natural repository. The recently published The Garden Plants of China begins, “Nowadays it is possible once more to visit most parts of China, to repeat and extend the journeys of the famous plant explorers of the past, and to collect many beautiful plants not previously brought into cultivation or, in many cases, even known” (Valder 1999). Such unbridled enthusiasm could substantially increase the number of species arriving into the United States without appropriate attention to the potential for these immigrant species to become invasive.
Economic signs are clear that trade with China is burgeoning. In the last decade, the value of agricultural imports from China has more than doubled—to $758 million in 1999 (USDA/ERS/FATUS 2001). This trade will probably increase. In November 2001, China hosted its first international exhibition in Beijing to promote the export of Chinese seed and germplasm. The increase in trade creates opportunities for the introduction not only of plants, but also of pathogens, such as those associated with crop species, and of insects, such as the Asian long-horned beetle, which arrived in wood packing material.
Almost all nonindigenous plants, arthropods, and pathogens in the United States were transported in the United States by humans. Natural introductions