Guides

Short guides to the USDA zone map, NOAA frost probabilities, and the extension calendars behind the planting windows. Each figure is tied to a named source.

• What changed in the 2023 USDA zone mapHow the 2023 Plant Hardiness Zone Map is built, what half-zones measure, and what the USDA said changed from 2012.
• Frost, freeze, and hard freezeNational Weather Service definitions of frost, freeze, and hard freeze, and how they differ from NOAA temperature thresholds.
• How frost-date probabilities workWhat the 10%, 50%, and 90% columns mean in the 1991–2020 NOAA climate normals, with Austin-Bergstrom as the worked example.
• Seed-starting timelineHow to count back from an outdoor planting window using a seed packet, with Texas A&M’s outdoor timing kept separate from indoor weeks.
• Protecting plants from a late frostWhat Iowa State Extension says about covers, and which crops Texas A&M times after the frost-free date.
• Fall vegetable garden timingHow Texas A&M’s fall planting chart uses regions, and how a first-frost date fits beside it.
• Garden microclimatesWhy a weather station a few miles away is not your backyard, using Oregon State’s notes on cold air and walls.
• Succession plantingThree succession methods from West Virginia University Extension, checked against Texas A&M’s planting windows and days-to-harvest ranges.
• Cool-season and warm-season cropsPenn State’s lists of cool-season and warm-season vegetables, and how a 32°F date sits next to them.
• Reading days to maturity on a seed packetWhat University of Maryland Extension says days-to-maturity count from, and how the fall calculator uses the number you type.