Zizotes milkweed, Asclepias oenotheroides
May go by these names: Zizotes milkweed, Hierba de Zizotes, Longhorn milkweed, Side-cluster milkweed, Primrose milkweed, Lindheimer's milkweed
Click the link above or the image below to be connected to the product page of an affiliate source of Zizotes seeds. Austin Native Seeds has a limited supply of fresh Zizotes seeds on their Etsy Store page as of February 3, 2020.
View Zizotes milkweed observations on iNaturalist
View Zizotes milkweed plant information at Wildflower.org
View Zizotes milkweed plant information at Plants.USDA.gov