Bagged Commercial Soils are an Avenue for Regional Dispersal of Weedy Plant Species

The spread of weedy plant species is a constant and increasing problem in the United States. A number of weed seed dispersal mechanisms are recognized, but one that may not have received attention is the potential for movement via the production and distribution of bagged soils for commercial sale. Our objective was to test the most common and inexpensive soils available at gardening supply stores in South Carolina for the presence of weeds. We identified 80 species or genera from 20 families in 19 different soil products. Most of the species were ubiquitous and many are restricted to the southern states, but some species are locally uncommon. We suggest the movement of different genotypes, even of common weeds, may create new evolutionary potential that could have long-term consequences for local adaptation of these species. The constant influx of weed seeds also creates propagule pressure and could contribute to further spread. We recommend commercial soil producers and distributors take steps to reduce the densities of viable weed seeds in their products.