As part of ongoing work on the Flora of the Southeastern United States (Weakley & Southeastern Flora Team 2022a) and related projects, as well as for general floristic, conservation, and scientific work in eastern North America, it is essential to document taxonomic and nomenclatural changes and significant distribution records. Here we describe three new species (in Rhynchospora, Sabulina, and Solidago), describe a new section (in Trichostema), make new combinations to treat taxa at appropriate ranks in appropriate genera and with appropriate nomenclatural application based on types (in Lycopodioides, Moeroris, Morella, Nellica, Tamala, and Trichostema), and propose the lumping of two species, resulting in a change in name and nativity status (in Sisyrinchium). These new combinations (rank changes, or generic transfers to apply newly accepted generic concepts to taxa that do not have corresponding available names at the appropriate rank) are needed to accurately reflect current taxonomic understanding of the regional flora. In the course of doing so, we discuss and address various nomenclatural issues, including typifications, and clarify characters and identification of difficult groups (providing new keys) in the regional flora. We also report significant new distribution and naturalization records in many genera, in New Jersey (taxa in the genera Anthriscus, Calibrachoa, Chaenomeles, Dichanthelium, Diplotaxis, Ditrichia, Dysphania, Erigeron, Eucommia, Eupatorium, Lepidium, Malus, Montia, Nepeta, Persicaria, Picea, Psammophiliella, Pulmonaria, Quercus, Silphium, Verbascum, Verbena, Vicia), in the Coastal Plain of Alabama and Mississippi (taxa in the genera Baptisia, Clematis, Coreopsis, Galium, Matelea, Mirabilis, Poterium, Rhynchospora, Silphium, and Symphyotrichum), in southern Indiana (taxa in the genera Andropogon, Brunnichia, Echinacea, Landoltia, Montia, Persicaria, and Solidago), and in North Carolina, Virginia, and likely other states (Euphorbia).