How we source data

Everything on this site is built from public data and published horticultural references. We do not copy text from other gardening sites — where a fact comes from a copyrighted source, we work from more than one reference and write it ourselves.

Outside the US: the ZIP, state, zone and region lookups use US government datasets, so they only cover the United States. The crop culture data, the calculators, the garden planner and the “My frost dates” calendar mode work anywhere in the world — use your own local average frost dates, which your national or regional gardening body publishes.

USDA PLANTS Database Public domain	Botanical names, families, and plant characteristics used on crop pages.
USDA Plant Hardiness Zone Map (2023) Public domain	The winter temperature bands and zone definitions used on zone pages and in the zone selector.
NOAA / NCEI freeze–frost date normals Public domain	The 32°F spring and fall frost "normals" behind the state averages and the calendar maths.
US land-grant Cooperative Extension planting guides Used as factual reference, written in our own words	Crop-by-crop sowing depth, spacing, germination temperature, days to maturity, and the week offsets relative to frost. Figures follow standard Cooperative Extension ranges; the core crops have been cross-checked against more than one state source, and the newer additions and the fruit chill/pollination data are on a rolling review.

Review cycle

Crop and guide pages carry a “last reviewed” date. We re-check the crop dataset and any guidance affected by changing recommendations at least once a year, and sooner if a source is updated.

Found an error?

If a date or figure looks wrong for your area, tell us on the contact page with your location and source. Corrections are the fastest way this gets better.