Data sources

PRISM Climate Group at Oregon State University / USDA-ARS

ZIP code to hardiness zone lookup, official zone temperature bands, and outdoor hardiness fit checks for catalog crops

Data pulled August 20, 2026

Michigan State University Extension

Place-backed frost midpoints for Michigan ZIPs in USDA zones 4a–6b. Outside Michigan, the same zone midpoints may appear only as a labeled zone proxy — not as Michigan Extension guidance for your state

Data pulled August 20, 2026

Virginia Cooperative Extension

Place-backed frost (Table 1) and crop×zone outdoor planting windows (tables 2–4) for Virginia ZIPs in zones 6a–8b. Not applied to other states that share the same USDA zone

Data pulled August 20, 2026 · Source updated August 24, 2026 (HTTP Last-Modified)

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NOAA National Centers for Environmental Information

Nationwide place-backed frost: 32°F / 50% last-spring (PRBLST) and first-fall (PRBFST) freeze dates from the nearest Climate Normals station to each ZIP/ZCTA. Primary outdoor calendar anchor for all states

Data pulled August 20, 2026 · Source updated August 22, 2026

Source was updated after our last pull — review needed.

U.S. Census Bureau

ZIP/ZCTA latitude–longitude used to join each ZIP to the nearest NOAA NCEI Climate Normals station when building the national frost table

Data pulled August 20, 2026 · Source updated September 10, 2025

Midwestern Regional Climate Center (cited by Virginia Extension SPES-673)

Optional Midwest/Northeast county exploration tool cited by Virginia Extension. Solanaceae uses NOAA NCEI station normals nationwide; MRCC remains a learn-more link for county nuance

Data pulled August 20, 2026

NC State Extension

Outdoor crop start dates for NC ZIPs: Eastern / Central / Western AG-756 calendars joined via Extension Gardener Handbook Fig. 9–1 Mountains / Piedmont / Coastal Plain county map (majority fill)

Data pulled August 20, 2026 · Source updated August 17, 2026

NC State Extension

County → Mountains / Piedmont / Coastal Plain for NC crop calendars (digitized choropleth with majority fill; split counties noted)

Data pulled August 20, 2026

Oregon State University Extension

County → Coast / Western valleys / High elevations / Columbia & Snake valleys for Oregon crop calendars (visual digitization; split counties noted)

Data pulled August 20, 2026 · Source updated December 20, 2024

Clemson Cooperative Extension

South Carolina home-garden hub; Piedmont / Coastal Plain planting dates come from HGIC Planning a Garden

Data pulled August 20, 2026 · Source updated August 24, 2026 (HTTP Last-Modified)

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Cooperative Extension frost-by-zone midpoints (MSU Extension, Virginia Cooperative Extension) on USDA PHZM zones

Fallback zone-proxy frost when the ZIP’s state does not have a place-matched Extension frost table wired. Place-backed paths use MSU (Michigan) or Virginia SPES-673 instead. Zones 1–3 and 9–10 are stepped estimates. Not NOAA station probabilities for your yard

Data pulled August 20, 2026

USDA Natural Resources Conservation Service

Species (and PLANTS infraspecific) scientific names, symbols, and profile links for each crop type

Data pulled August 20, 2026 · Source updated March 6, 2026

USDA Agricultural Research Service, National Plant Germplasm System

Botanical crop groups and infraspecific taxa (e.g. romaine vs butterhead lettuce) when more specific than the PLANTS species profile

Data pulled August 20, 2026

USDA National Agricultural Library

Curated links to Cooperative Extension planting, companion, and seed-start guides used throughout the planner

Data pulled August 20, 2026 · Source updated August 24, 2026 (HTTP Last-Modified)

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West Virginia University Extension (linked by USDA NAL)

Companion and antagonist plant pairs, plus keep-apart spacing (foes at least two to three rows apart ≈ 3 ft edge-to-edge on the bed grid)

Data pulled August 20, 2026

University of Minnesota Extension (linked by USDA NAL vegetable gardening)

Research-backed companion planting practice (space sharing, three sisters mutual support, and insect-management notes) alongside the WVU Friend or Foe chart

Data pulled August 20, 2026 · Source updated August 24, 2026 (HTTP Last-Modified)

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Rutgers New Jersey Agricultural Experiment Station

Typical between-row vegetable spacings used to interpret WVU’s two-to-three-rows keep-apart guidance as about 3 ft of clear bed space

Data pulled August 20, 2026

USDA National Agricultural Library

Corn, bean, and squash companion relationship

Data pulled August 20, 2026 · Source updated August 24, 2026 (HTTP Last-Modified)

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Oregon State University Extension

Table 1 outdoor planting date ranges by four Oregon growing regions for OR ZIPs matched via digitized EC 871 region map

Data pulled August 20, 2026 · Source updated August 24, 2026 (HTTP Last-Modified)

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Kansas State University Research and Extension

Statewide primary bar planting windows for most of Kansas (earliest week of each dark primary bar); MF312 tomato southeast / east-central / northwest transplant dates via NCEI last-spring frost band

Data pulled August 20, 2026 · Source updated May 2, 2024

University of Illinois Extension

North / Central / South Illinois outdoor planting tables; region join from NCEI last-spring frost vs ISWS regional median bands

Data pulled August 20, 2026 · Source updated August 24, 2026 (HTTP Last-Modified)

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Iowa State University Extension

Central Iowa baseline outdoor planting dates with ±1 week offsets for NASS crop reporting district county roster (Northern / Central / Southern Iowa)

Data pulled August 20, 2026 · Source updated August 24, 2026 (HTTP Last-Modified)

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Alabama Cooperative Extension System

North / Central / South Alabama outdoor planting tables via USDA Ag Statistical District county roster (ANR-1165 / ANR-0063)

Data pulled August 20, 2026 · Source updated May 29, 2025

Oklahoma State University Extension

Southeast / Northeast / West–South / West–North warm-season planting quadrants via OHCE Extension district county roster

Data pulled August 20, 2026

University of Wisconsin Division of Extension

Southern Wisconsin baseline outdoor planting dates with cited ± week offsets for Central and Northern bands via NCEI last-spring frost

Data pulled August 20, 2026

University of Nebraska–Lincoln Extension

Eastern / Central / Western Nebraska outdoor planting tables; region join from NCEI last-spring frost vs UNL regional frost-map bands

Data pulled August 20, 2026 · Source updated August 24, 2026 (HTTP Last-Modified)

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University of Maryland Extension

Central Maryland outdoor planting baseline with ±1–2 week shift from NCEI frost-free growing-season length (early / central / late bands)

Data pulled August 20, 2026 · Source updated August 24, 2026 (HTTP Last-Modified)

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University of Georgia Cooperative Extension

Middle Georgia baseline outdoor planting dates with ±2 week North / South offsets via NCEI last-spring frost band

Data pulled August 20, 2026 · Source updated March 25, 2024

University of Arkansas System Division of Agriculture

Statewide Arkansas outdoor planting date ranges (earliest day of each published warm-season range)

Data pulled August 20, 2026

University of California Cooperative Extension / Master Gardener Program

Partial outdoor planting months for CA ZIPs in explicitly named coastal counties (Monterey north, SLO south) and Imperial County; earliest day of first month in each range

Data pulled August 20, 2026 · Source updated August 24, 2026 (HTTP Last-Modified)

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Clemson Cooperative Extension Home & Garden Information Center

Explicit Piedmont and Coastal Plain county lists and Table 1 outdoor planting date ranges for South Carolina ZIPs matched to those counties

Data pulled August 20, 2026 · Source updated August 24, 2026 (HTTP Last-Modified)

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Mississippi State University Extension

Figure 2 planting Areas 1–5 (county map digitization) and Tables 6–7 outdoor planting dates for Mississippi ZIPs

Data pulled August 20, 2026 · Source updated August 7, 2025

University of Missouri Extension

Figure 1 North / Central / South planting regions (county map digitization; Ozark Plateau uses North dates per publication text) and Table 2 outdoor planting dates for Missouri ZIPs

Data pulled August 20, 2026

University of Florida IFAS Extension

North / Central / South outdoor planting date columns (Table 1); regions prefer the SFYL gardening region county map, with Census ZCTA latitude vs State Road 40 / 70 corridor proxies as fallback (VH021 footnote)

Data pulled August 20, 2026

Ohio State University Extension

Zone 6a warm-season transplant outdoor starts after May 15; adjust 1 week earlier for 6b and 1 week later for 5b

Data pulled August 20, 2026 · Source updated August 24, 2026 (HTTP Last-Modified)

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University of Idaho Extension

Table 1 outdoor transplant / direct-sow ranges by USDA zones 3–4 / 5–6 / 7; earliest day of each range for Idaho ZIPs

Data pulled August 20, 2026

University of Rhode Island Cooperative Extension

Statewide half-month outdoor transplant / direct-sow marks for Rhode Island (frost anchors May 15 / October 15)

Data pulled August 20, 2026

University of Delaware Cooperative Extension

Statewide outdoor planting date ranges for Delaware (Suggested Garden Plan / HG-34 lineage); earliest day of each range

Data pulled August 20, 2026 · Source updated August 24, 2026 (HTTP Last-Modified)

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LSU AgCenter

North / South outdoor planting date table for Louisiana; region join from P3761-A (USDA 8a/8b → North/Central; 9a/9b → South)

Data pulled August 20, 2026

Texas A&M AgriLife Extension

Table 1 average fall planting dates by Texas gardening Regions I–V; Table 3 maps those regions to USDA hardiness zones. Spring outdoor dates use Home Vegetable Gardening Guide Table 8 weeks after frost-free date anchored to NCEI last-spring frost

Data pulled August 20, 2026 · Source updated December 15, 2025

University of Kentucky Cooperative Extension

Figure 20.8 Western / Central / Eastern planting regions (high-confidence county digitization) and Table 20.15 earliest/latest outdoor planting dates

Data pulled August 20, 2026

Michigan State University Extension

Month-by-month outdoor planting lists for Lower Peninsula (Zone 6a base) and Upper Peninsula (Zone 4b base), with cited USDA zone week offsets; peninsula join uses Michigan’s 15 Upper Peninsula counties

Data pulled August 20, 2026

University of Minnesota Extension (USDA NIFA / cited by USDA NAL)

Indoor seed-start lead times before outdoor planting for vegetables and flowers

Data pulled August 20, 2026 · Source updated August 24, 2026 (HTTP Last-Modified)

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Virginia Cooperative Extension

Fall succession into the same beds after spring crops finish—count back from first frost (days to maturity + fall factor) without building a separate fall garden map

Data pulled August 20, 2026 · Source updated March 20, 2026

University of Minnesota Extension

Indeterminate tomatoes keep flowering and ripening until cold weather; determinate types finish in about four to six weeks — used to treat tomato harvest as a range through frost

Data pulled August 20, 2026 · Source updated August 24, 2026 (HTTP Last-Modified)

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Virginia Cooperative Extension

Relay / succession planting notes for short-yielding crops such as cucumbers (about two weeks from one planting) that support finite harvest windows rather than until-frost picking

Data pulled August 20, 2026 · Source updated August 24, 2026 (HTTP Last-Modified)

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University of Minnesota Extension

Typical yield-per-plant ranges for household planning, plus harvest-window lengths after first ripe fruit (e.g. indeterminate tomatoes 8–10 weeks, field cucumbers ~3 weeks, bush beans 3–4 weeks)

Data pulled August 20, 2026 · Source updated August 24, 2026 (HTTP Last-Modified)

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U.S. Census Bureau

ZIP/ZCTA → county of largest land overlap for Extension region lookup (ZCTA is not always identical to USPS ZIP)

Data pulled August 20, 2026 · Source updated August 24, 2026 (HTTP Last-Modified)

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Zippopotam.us (city and state only)

City and state labels shown with your ZIP code

Data pulled August 20, 2026 · Source updated August 24, 2026 (HTTP Last-Modified)

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