Growing media as a pathway for alien plant introductions
The movement of growing media, either on its own or in association with plants for planting can be a pathway for pests. In 2025, inspections of 20 importing facilities in the Netherlands were conducted where potted plants were inspected and suspected plant contaminants were collected for further analysis. In addition, coco peat samples were collected from a known contaminated batch and sampled for the presence of alien plant species. Coco peat is often used as a growing media for potted plants, is also imported as a standalone commodity and can be an additional pathway of introduction of non-native plants. The survey resulted in the interception of a number of regularly detected species as contaminants of potted plants including Alternanthera philoxeroides (Amaranthaceae, EPPO A2 List), Humulus scandens (Cannabaceae, EPPO A2 List) and Lygodium japonicum (Schizaeaceae, EPPO A1 List). Two species Microstegium vimineum (Poaceae, EPPO A2 List) and Broussonetia papyrifera (Moraceae, EPPO List of Invasive Alien Plants) were recorded as a contaminant of potted plants for the first time. Parthenium hysterophorus (Asteraceae, EPPO A2 List) was identified as a contaminant of coco peat from Sri Lanka. These findings demonstrate the risks of contaminated growing media and emphasize the critical need to prioritize inspections of these overlooked pathways.
Sources
Van Valkenburg JLCH, Beyer JL, Piet LF (2026) Broussonetia papyrifera (L.) L’Hér. ex Vent., Microstegium vimineum (Trin.) A. Camus and Parthenium hysterophorus L. imported into the Netherlands via potted ornamentals or their coco peat substrate. EPPO Bulletin (early view). https://doi.org/10.1111/epp.70130