Data sources

• USDA ARS 2023 Plant Hardiness Zone Map — ZIP-to-zone data via the PRISM Climate Group (public domain)
• NOAA 1991–2020 U.S. Climate Normals, supplemental freeze/frost products (public domain)
• UMD Extension — When to Plant Vegetables (central Maryland calendar)
• Cornell Cooperative Extension Albany — first planting dates

All data was retrieved 2026-10-04. Site generated from the compiled dataset; every date on this site traces to those files.