- BONAP's Taxonomic Data Center
The Biota of North America Program maintains a searchable database of vascular flora. It can be searched by family, genera, or species. Geographic search terms are available and detailed down to county and zip code.
- Lady Bird Johnson Wildflower Center
The Lady Bird Johnson Wildflower Center maintains a Native Plants Database for North America that includes over 25000 species. Search options have habit, lifespan, light requirements, soil moisture, and bloom and leaf characteristics. Geographic search is at the state level.
- Missouri Botanical Garden Plant Finder
It has extensive descriptions of plants and advanced search features, including wildlife attractions, maintenance levels, uses, and other features. Geographic search is by zone, and native information is available only for Missouri.
- USDA PLANTS
The USDA's Plant List of Attributes, Names, Taxonomy, and Symbols provides information about the vascular plants, mosses, liverworts, hornworts, and lichens of the United States. This is a work in progress, but it already has robust search and filter features. Geographic search features are at the state or regional level. There is partial information on invasive and noxious species and native plants.