About PlantingCalc
PlantingCalc provides free gardening calculators powered by USDA hardiness zone data, NOAA frost dates, and agricultural extension research. Every tool on this site is designed to help home gardeners make data-driven decisions—from soil preparation to harvest timing.
Our Data Sources
- USDA Plant Hardiness Zone Map (via phzmapi.org) — determines your growing zone by ZIP code
- NOAA Frost Date Normals — average first and last frost dates for accurate planting windows
- University Agricultural Extension Publications — peer-reviewed spacing, fertilizer, and watering guidelines
- Plant-Harmony Companion Planting Database — research-backed companion and antagonist plant pairings
Why Trust Our Calculators
- Real government data — USDA zones and NOAA frost dates, not guesswork
- Open-source plant databases — transparent, verifiable information
- Transparent methodology — every calculation explains how it works
- Regularly updated — data refreshed to reflect the latest USDA and NOAA releases
Who We Are
Built by gardeners and data analysts who believe everyone deserves access to the same planning tools professional growers use.