Plant naturalizations and invasions in the Eastern United States: 1634-1860.
Plant immigrants to North America arrived from Europe with the first human immigrants, products of the intense incentive early colonists felt to transplant European agriculture into the Western Hemisphere. Among early deliberate and accidental introductions were species that would soon become naturalized in eastern North America: Artemisia absinthium, Hyoscyamus niger, Plantago lanceolata, and Taraxacum officinale. The naturalized flora grown as species for food, forage, seasonings, and medicine were imported, cultivated, and escaped the bounds of cultivated fields. Importation of what has become the most common category of naturalized species, erstwhile ornamentals, had a modest beginning by the mid-seventeenth century. The first recorded invasion, the spread and proliferation of Linaria vulgaris in the Mid-Atlantic colonies, was recognized by the mid-eighteenth century, and Berberis vulgaris was rampant in southern New England before 1800. Botanical records, including published floras, became much more common in the first decades of the nineteenth century and revealed a naturalized flora in the U.S. that was quite similar in composition to the agricultural weed flora of Western Europe. Many ruderals and agricultural weeds were widespread in the eastern U.S., but probably not invasive by 1860, and included Bromus secalinus, Cynoglossum officinale, Galium aparine, and Senecio vulgaris. Other alien species had, however, become invasive by the 1840s, such as Echium vulgare in Virginia. Species that were to form devastating invasions in the United States from 1860 onward (e.g., Bromus tectorum, Euphorbia esula, Lonicera japonica, and Melaleuca quinquenervia) had either not arrived by 1860, were undetected, or were not reported as having escaped from cultivation. Growth of the naturalized flora and the subsequent number of invasive taxa was certainly facilitated, and probably sparked, by the enormous growth of railroads and rail-borne commerce in the late-nineteenth century.