Sources
Data sources and credits
Where every number on this site comes from, with dates and licenses.
USDA NRCS PLANTS Database
- What we use
- County distribution records (county distribution downloads), native status for the lower 48, Alaska, Hawaii and Puerto Rico (PLANTS map service), plant profiles (names, family, growth habit, duration) and plant characteristics.
- Where
- https://plants.usda.gov/
- License
- CC0 public domain dedication, per the PLANTS record in the data.gov catalog.
- Retrieved
- November 4, 2026
- Citation
- USDA, NRCS. 2026. The PLANTS Database (https://plants.usda.gov, 11/04/2026). National Plant Data Team, Greensboro, NC USA.
Kew’s World Checklist of Vascular Plants (WCVP)
- What we use
- Native or introduced status by state (WGSRPD level-3 areas), matched to PLANTS species by accepted name. A species is listed in a state only where WCVP records it as native there.
- Where
- http://sftp.kew.org/pub/data-repositories/WCVP/wcvp.zip (data file dated June 4, 2026)
- License
- WCVP README: “Licensed under http://creativecommons.org/licenses/by/3.0”.
- Retrieved
- November 4, 2026
- Citation
- Govaerts R. (ed.) (2026). WCVP: World Checklist of Vascular Plants. Facilitated by the Royal Botanic Gardens, Kew. Data file dated 2026-06-04, http://sftp.kew.org/pub/data-repositories/WCVP/ (retrieved 2026-11-04). Paper: Govaerts R. et al. (2021) The World Checklist of Vascular Plants, a continuously updated resource for exploring global plant diversity. Scientific Data 8, 215.
USGS US-RIIS
- What we use
- United States Register of Introduced and Invasive Species (US-RIIS) (ver. 2.0, November 2022). Species it lists as introduced in the lower 48, Alaska or Hawaii are left off the native lists there.
- Where
- https://doi.org/10.5066/P9KFFTOD
- License
- CC0 1.0 (USGS public domain dedication).
Hardiness zones by ZIP
- What we use
- The 2023 USDA Plant Hardiness Zone Map ZIP code table (a USDA ARS and Oregon State University product).
- Credit
- PRISM Group, Oregon State University, https://prism.oregonstate.edu, accessed November 3, 2026.
- Terms
- Free to reproduce and distribute with this citation. Plant zones on this site are our own estimate and are not the official USDA map.
ZIP codes, counties and the state map
- ZIP areas
- U.S. Census Bureau ZIP Code Tabulation Areas (2023 Gazetteer, 2020 ZCTAs) and the 2020 ZCTA-to-county relationship file. Public domain.
- Boundaries
- U.S. Census Bureau cartographic state boundaries, 2024 (1:20 million). Public domain.
Photo credits
Photographs are licensed stock images used for illustration on the matching plant pages. They are not records of where a plant grows.
- Purple coneflower (Echinacea purpurea) in bloom: Depositphotos, asset page, Standard license.
- Little bluestem (Schizachyrium scoparium) clump on a gravel bar: Shutterstock, asset page, Standard license.
- Butterfly milkweed (Asclepias tuberosa) in bloom: Depositphotos, asset page, Standard license.
The hero and spot illustrations are original artwork made for this site; they are decorative, not plant identification images.
Independent site
Natives by ZIP is an independent reference site. It is not affiliated with or endorsed by the USDA, NRCS, the Census Bureau, Oregon State University or any government agency.