Laundry washing increases dispersal efficiency of cloth-dispersed propagules.
Due to increased human mobility, cloth-dispersed propagules can be transported over long distances, which would not have been bridged otherwise. We studied a potentially important component of human-mediated seed dispersal by assessing the effects of laundry washing on the dispersed propagules. We studied the germination of 18 species, which have morphological adaptations for epizoochory and are commonly dispersed by people. We tested six treatments (washing with water, soap nut or detergent, at 30°C or 60°C) compared to an untreated control. Washing intensity was the most significant factor affecting germination. Washing at 30°C was neutral for 14 species, suppressed one species and supported three species. Washing at 60°C decreased seedling numbers of half of the studied species. The intensive washing treatments at 60°C significantly decreased the synchrony of germination. We showed that people are not purely transporting propagules from one location to another, but via the laundry cycle, we can also influence the fate of the transported propagules by affecting germination potential, seedling fitness and germination dynamics. These results have new implications for understanding the early stages of biological invasions and call for improved biosecurity measures in nature reserves subjected to a growing pressure of tourism.