Yes — Strong Match
napa cabbage (zones 2-11) covers every zone Idaho contains (3b-8a), so hardiness is not what limits it anywhere in the state.
Napa Cabbage in Idaho — the short answer
Napa Cabbage in Idaho: hardy in zones 2–11, full sun, against a state median of ~160 frost-free days.
- Plant zones
- 2-11
- Manual horticultural correction (source not retained); NC State Extension and Missouri Botanical Garden, with the remaining rows from other published sources or Growable Ground compilation
- Idaho zones
- 3b-8a
- USDA PHZM 2023
- Frost window
- Apr 26 - May 17 – Oct 1 - Oct 17
- NOAA RCC ACIS 1991-2020, 28°F
- Shortest county season
- 94 days
- NOAA Regional Climate Centers ACIS, 1991-2020, county 28°F killing freeze
- Days to maturity
- 70 days
- Growable Ground Plant Database
Plant data: Growable Ground Plant Database, compiled from FAO ECOCROP, USDA PLANTS and university Extension sources — per-field provenance varies and is published with the dataset.
Your yard isn't the whole zone.
Napa Cabbage is grown as an annual, so your winter zone isn't the deciding factor — your frost-free window is. A typical Idaho site runs ~160 frost-free days, but that is a state median, not your yard: slope, trees, and low spots move the last-frost date across a single parcel. Enter your address and we'll score napa cabbage against your land's actual frost dates, sun, and soil.
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Idaho is not one climate
Idaho’s winter-low ladder runs across 44 counties, from zone 5 in Bear Lake County to zone 7 in Payette County. That is 20°F between the two counties’ average coldest night — the difference between napa cabbage overwintering in the ground and coming under cover.
The middle half of 44 counties runs 5.5–6.5 zones, with a median of 6 zones — a 2-zone span end to end.
Measured across 44 Idaho counties. USDA PHZM 2023, per county. Quartiles are order statistics — every figure shown is a value a real county recorded, not an interpolation. Your own site sits somewhere inside this range; a parcel report resolves where.
Where in Idaho Fits Best
Even within Idaho's zones 3b-8a, county microclimates differ enough to change what thrives. These counties carry the closest zone match for napa cabbage (USDA PHZM 2023):
Zone Comparison
Napa Cabbage Needs
- USDA Zones: 2-11
- Frost-Free Days: 40+
- Sun: Full Sun
- Mature size: 1.5 ft tall
- Picking window: ~14 days of harvest
- Drought tolerance: Low
Idaho Has
- USDA Zones: 3b-8a
- Last Hard Freeze (28°F): Apr 26 - May 17
- First Hard Freeze (28°F): Oct 1 - Oct 17
- Annual Rainfall: 8-35 inches
- Common Soils: Volcanic ash, Silt loam, Sandy loam
Plant Zone Range (zones 2-11)
Preferred Soil pH
Plant data: Growable Ground Plant Database, compiled from FAO ECOCROP, USDA PLANTS, and university Extension sources — per-field provenance varies and is published with the dataset. State data: USDA ARS PHZM 2023, NOAA Climate Normals, NRCS SSURGO.
When to Plant Napa Cabbage in Idaho
The frost window
Across Idaho, the last spring hard freeze (28°F) clears between Apr 26 and May 17, and the first fall hard freeze lands between Oct 1 and Oct 17 (NOAA Regional Climate Centers ACIS, 1991-2020). Counting from the latest last freeze to the earliest first freeze, that's a 137-day window you can count on — up to 174 days on a mild site in a kind year. That marks the hard freeze, not the last light frost, so tender transplants usually wait another 2-3 weeks.
When to start the seed
Those dates are when napa cabbage goes out, not when it starts. It is sown under cover about 4 weeks ahead, so counting back from Idaho's late-side last freeze of May 17 is what fixes your sowing date — and a yard that clears frost earlier than the state's late date starts earlier still.
Days to maturity vs. the window
At 70 days to maturity (Growable Ground Plant Database), counting from the last hard freeze it ripens with 67 days to spare even in Idaho's tightest freeze scenario — room for a later start or a second sowing.
Frost window: NOAA Climate Normals 1991-2020. Plant timing fields: Growable Ground Plant Database — frost-free days from FAO ECOCROP, days to harvest from university Extension production guides, and growing-degree-day and chill-hour minimums that are compilation estimates rather than published figures. Your site's own frost dates can run earlier or later than the state range — a parcel report pins them down.
Growing Season Fit
The zone check says napa cabbage survives winter here. Whether the season is long enough — and warm enough — is a different question.
Frost-free days
Napa Cabbage wants 40+ frost-free days; a typical Idaho site sees ~160 (NOAA Regional Climate Centers ACIS, 1991-2020). That leaves comfortable headroom for succession planting.
Growing degree days
Napa Cabbage needs ~1300 GDD (base 50°F) to ripen. The state median runs ~1187 GDD (from PRISM 1991-2020 climate normals), so Idaho's typical season runs short on heat — pick a south-facing site and consider season extension.
GDD and chill-hour figures are computed from PRISM 1991-2020 monthly climate normals; frost-free days from NOAA Regional Climate Centers ACIS, 1991-2020. Each is the state median across its counties (P25/P75 span the within-state spread). Hardiness-zone range is USDA PHZM 2023.
Soil + Drainage Fit
Napa Cabbage likes near-neutral soil (pH 5-7). That's the common-ground band across Idaho's volcanic ash and silt loam — a soil test confirms it for your site. It will grow across that whole span, but it does best between pH 5.5 and 6.5 — worth knowing before you decide whether a Idaho soil test result is a problem or just a number. Drainage matters: this plant wants well (dry spells). If your Idaho site is heavier clay or sits in a low spot, raised beds or amendment with compost solve it.
Plant pH requirements: FAO ECOCROP and USDA PLANTS, with the remaining rows from other published sources or Growable Ground compilation. Drainage: FAO ECOCROP, with the remaining rows from other published sources or Growable Ground compilation. Idaho soil profile from USDA NRCS SSURGO. Site-specific verification: a 30-minute soil test from your local Extension lab.
Before you plant napa cabbage for food
Anything you grow to eat takes up what is in the ground it grows in, so what is on record near you is worth knowing before napa cabbage goes in. What follows is Idaho’s documented federal record at state scale — a screening signal, not a soil test, and not a statement about any one lot.
Safe to Grow Here?
What the federal record shows across Idaho — and how to grow with it.
We checked the federal record across Idaho — 21,100 documented sites across 8 of the 9 source types we track.
The most significant on record: 215 Superfund sites. Sites tracked in EPA's Superfund program — from assessment-stage CERCLIS entries to confirmed National Priorities List cleanup sites.
Idaho carries one of the heavier federal records we track — and that's not a verdict on your yard. Proximity to a documented site is information, not a diagnosis: nothing here says any particular parcel is affected. It does earn one concrete step — before food beds go in the ground, a professional soil test tells you exactly what you're working with, and raised beds with clean imported soil grow well almost anywhere in the meantime.
Severity Distribution
across Idaho
Highest-Severity Sites
A note from Gnorman
What an experienced grower watches for around here
In and around Idaho, two things run higher than the national average across Idaho — Mining (3,980 sites) and Nitrate (9,840 sites). Knowing it is half the work — and it's nothing a thoughtful grower can't plan for.
Mining: Mining sites — both historic and active — can leach heavy metals (arsenic, lead, cadmium, mercury) into soil and water for centuries after operations cease.
Nitrate: Nitrate contamination primarily comes from agricultural fertilizer runoff and failing septic systems.
Test soil for heavy metals (lead, arsenic, cadmium, mercury) — this is essential near any mining site.
Test well water for nitrate if you rely on a private well for irrigation (EPA standard: 10 mg/L).
Sources: EPA, USGS — 1.8M documented sites tracked nationwide across 9 federal source types.
What Else to Consider for Napa Cabbage in Idaho
Zone compatibility tells you about winter cold survival — but Idaho growers also need to think about:
Short growing season at higher elevations
Arid conditions require irrigation in most of the state
Cold winter snaps can reach -30F in mountain valleys
What to actually do about these — and the constraints that apply to every Idaho grower, not just napa cabbage — is covered on the Idaho growing guide.
Timing shifts within Idaho
Napa Cabbage needs about 40 days of frost-free season to complete its cycle. Even Valley County — Idaho’s shortest season at 94 frost-free days — clears that by 54 days, so season length isn’t the constraint anywhere in Idaho. What varies is your own parcel.
Across Idaho’s 44 counties the frost-free season runs from 94 days in Valley County to 216 days in Nez Perce County — a spread of 122 days, which is why a single statewide planting date misleads. The median Idaho county sees 160 frost-free days, leaving napa cabbage about 120 days of slack on a typical parcel — room for a second sowing where the season runs long.
County last-freeze dates and frost-free day counts: NOAA Regional Climate Centers ACIS (1991-2020), county 28°F freeze (earlier than the folk 32°F "last frost"). Napa Cabbage's 40-day requirement: USDA PLANTS / Growable Ground plant database (minimum frost-free days). A parcel report resolves your address's own frost dates.
Pollinator + Wildlife Value
Napa Cabbage draws honeybees and native bees (moderate value, Growable Ground Plant Database). Planting it near vegetable beds can lift fruit set on neighboring crops. Outdoors, napa cabbage can only work that bloom inside Idaho's frost window — roughly 160 days, opening after the last 28°F freeze (Apr 26 - May 17) and closing at the first (Oct 1 - Oct 17), per NOAA Regional Climate Centers ACIS, 1991-2020.
Idaho Cooperative Extension
For Idaho-specific cultivar recommendations, planting calendars, and pest pressure for napa cabbage, the canonical source is University of Idaho Extension. Their fact sheets carry the local trial data we can't generalize across 50 states.
Is Napa Cabbage native to Idaho?
No — the USDA PLANTS Database lists Napa Cabbage as introduced rather than native in the Lower 48, so it is not part of Idaho's native flora. It grows here as a garden plant; pairing it with a few Idaho natives keeps local pollinators fed too.
Looking for plants that belong here? The Idaho growing guide lists USDA-documented natives for the state.
Native-range data: USDA PLANTS Database state-distribution records, accessed 2026-07-01.
Common Questions About Growing Napa Cabbage in Idaho
When can I plant Napa Cabbage in Idaho?
Idaho's last spring hard freeze (28°F) clears between Apr 26 and May 17, and the first fall hard freeze lands between Oct 1 and Oct 17 (NOAA Regional Climate Centers ACIS, 1991-2020). Time outdoor planting to after the last hard freeze for your specific site — a further two to three weeks for anything tender — and count back from those dates for transplant scheduling.
Can Napa Cabbage mature before first frost in Idaho?
Yes — Napa Cabbage matures in 70 days (Growable Ground Plant Database), and Idaho's dependable hard-freeze-free window runs 137 days (NOAA Regional Climate Centers ACIS, 1991-2020), leaving 67 days of margin. Plant once the last hard freeze has passed — two to three weeks later for anything tender — and it ripens ahead of the first fall freeze.
What hardiness zone is Napa Cabbage grown in across Idaho?
Idaho spans USDA hardiness zones 3b-8a (USDA ARS PHZM 2023). Napa Cabbage carries a range of zones 2-11, so the overlap zones are where outdoor growing is most reliable.
How many frost-free days does a typical Idaho site have?
A typical Idaho site sees ~160 frost-free days per year (derived from NOAA Regional Climate Centers ACIS, 1991-2020). Napa Cabbage needs 40+ frost-free days, so check whether your local microclimate runs above or below the state average before settling on a planting date.
Is Napa Cabbage native to Idaho?
No — the USDA PLANTS Database lists Napa Cabbage as introduced rather than native in the Lower 48, so it is not part of Idaho's native flora. It grows here as a garden plant; pairing it with a few Idaho natives keeps local pollinators fed too.
How should I amend the soil for Napa Cabbage in Idaho?
Napa Cabbage prefers pH 5-7 and well (dry spells) drainage (FAO ECOCROP). That sits in the common-ground band across Idaho soils — a 30-minute soil test from a local Extension lab confirms it for your specific site.
Will Napa Cabbage actually grow on my specific land in Idaho?
State-level zone + climate data is a sketch. A Growable Ground parcel report scores napa cabbage against your address's exact soil pH, drainage, sun, and frost-date data drawn from USDA SSURGO, NOAA, and PRISM — not state averages.
Check your specific parcel in Idaho
State-level data is a sketch. Your Growable Ground report scores napa cabbage against your parcel's exact soil, sun, drainage, and frost data — not zone averages.
Three things about your lot that Idaho napa cabbage averages can't show:
We read public map data around Idaho — soil, climate, flood, and parcel records. How we handle your address.
25+ data sources read at your address, not the Idaho napa cabbage average
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