Cyperus entrerianus (Boeckler) (deeprooted sedge, deeproot sedge, woodrush flatsedge) has become naturalized throughout the Texas coastal prairie ecoregion and is now found throughout much of the southeastern United States. Originally from Argentina, its successful naturalization is linked to its rapid growth, morphological plasticity, and generalized habitat requirements, but little work has focused upon its seed biology or ecology. Research was conducted to quantify phytomorphological variability, develop seed yield prediction models, and quantify germination requirements for C. entrerianus to aid in future control and management efforts of this exotic invasive sedge, particularly those focused upon seedbanks. Cyperus entrerianus phytomorphology, seed production, and seed germination were extremely variable among study areas, and provide evidence for its successful naturalization. Although plants varied morphologically, spike cluster area and inflorescence diameter explained much of the variation in seed biomass production. Seed yield prediction models will be useful in monitoring seed production throughout its naturalized range. We estimated that 1300–3100 kg ha⁻¹ seeds could be produced in monotypic stands, although germination rates varied among study areas as well. Seeds collected from larger plants in sites that produced more seeds showed germination rates > 85%. Seeds exposed to imbibition and chilling treatments had reduced germination, although no seed treatments (imbibition, chilling, combinations thereof) depressed germination rates below 63%. Immediate and short-term control and management efforts should focus upon interruption of seed production, via aboveground plant removal, but long-term efforts must target seedbank management. Although seed longevity is not known, seedbank depletion and subsequent integrated management using herbicides and prescribed fire will be required for local and large scale control efforts.