Riley, L.E.; Klocke, A. 2018. Propagation protocol for production of container (plug) Penstemon deustus Dougl. ex Lindl. plants 164 ml (10 in³) container. Native Plant Network. U.S. Department of Agriculture, Forest Service, National Center for Reforestation, Nurseries, and Genetic Resources. http://npn.rngr.net/propagation/protocols [Accessed 2020 June 5].