Methodology

How GrowZone turns a ZIP code into a planting calendar.

GrowZone maps supported ZIP codes to a representative frost station and USDA hardiness zone, then applies crop-specific timing rules.

1. ZIP to representative station

Each supported ZIP is assigned to a representative station with last-frost and first-frost estimates. This is not a guarantee; it is a planning signal.

2. Station to crop windows

Each crop has timing rules for seed starting, transplanting, direct sowing, and harvest. Warm-season crops wait longer after frost than cool-season crops.

3. USDA and NOAA ingestion cadence

The production dataset is designed as a canonical ZIP x USDA-zone x frost-window table. USDA Plant Hardiness Zone GIS inputs are refreshed annually, or sooner when USDA publishes a new map release. NOAA/NWS climate-normal and representative frost-station inputs are recomputed before the February-May seed-starting peak and again before fall-planting content. Each generated page carries the current source/version date so stale data is visible instead of hidden.

4. Local verification

Gardeners should verify with local cooperative extension guidance, especially for unusual microclimates, high-value crops, or current-year weather anomalies.

5. Measurement

GrowZone reports canonical metrics through /api/metrics and partner API hooks. The metric keys are sessions, organicSessions, pageviews, indexedPages, emailSignups, affiliateClicks, affiliateRevenue, adRevenue, and rpm. GA4 is optional and never replaces the canonical metrics contract.