Germination of Invasive Plant Seeds after Digestion by Horses in California

Quinn, Lauren; Kolipinski, Mietek; Coelho, Vania; Davis, Bonnie; Vianney, John-Mary; Batjargal, Orgiltuya; Alas, Monika; Ghosh, Sibdas

A study with the goal of establishing the ability of seeds to germinate from horse feces using a unique method that removed any potential contamination. Using a unique sterile design intended to eliminate outside seed contamination of horse feces, we investigated whether weed seeds germinate after digestion by horses. Feces were collected from selected National Parks and other locations in central and northern California. All potted fecal samples were irrigated and grown in an enclosed sterile nursery environment. Thirty-two plant species emerged from these fecal samples, 24 of which were not native to California. None of these were identified on the California Department of Agriculture’s Noxious Weed List, which is used as a basis to certify equine feed as weed free. However, seven of the non-native species are identified as moderately invasive on the California Invasive Plant Council’s (Cal-IPC) list. These species are: Hirschfeldia incana, Hordeum marinum, Lolium multiflorum, Mentha pulegium, rumex acetosella, Trifolium hirtum, and Vulpis myuros. In addition, the following four non-native plants are listed at the limited invasiveness level on the Cal-IPC list: Hypochaeris glabra, Lythrum hyssopifolium, Medicago polymorpha, and poa pratensis. Because we did not survey invasive plant cover in locations from which we sampled, we cannot guarantee that species identified in our samples would have also germinated in the field. Out results add to a growing body of literature documenting germination of seeds after passing through the digestive system of horses and suggest that the current list of noxious weeds certify weed-free feed for equines should be comprehensive.

Germination of Invasive Plant Seeds after Digestion by Horses in California

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