The Snake River Plain spans USDA hardiness zones 5a-7a — enough range to grow cool-season vegetables, hardy fruit, and warm-season crops that mature before the first hard frost.
A broad volcanic plain of deep ash-rich soils and long summer days, irrigated from the Snake River — the classic Idaho potato, hop, and sugar-beet country. On paper, potato, lentil, apple, and hop all suit these conditions — on the ground, soil, sun, and drainage make the final call.
The Snake River Plain spans Idaho. Its footprint follows the EPA Level III ecoregion boundary; the counties linked below are representative of the region, not an exhaustive list.
Your yard isn't all of the Snake River Plain.
The Snake River Plain spans USDA zones 5a-7a, but your parcel sits in exactly one — and slope, tree cover, and low spots nudge it further. Enter your address and we'll score 1,086 plants against your land's actual soil, sun, and frost.
We read public map data around Snake River Plain — soil, climate, flood, and parcel records. How we handle your address.
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The Snake River Plain — the short answer
The Snake River Plain: USDA zones 5a-7a, 133–205 frost-free days depending where in it you stand, in Idaho.
- USDA zones
- 5a-7a
- USDA PHZM 2023, aggregated over the footprint
- Shortest season here
- 133 days
- NOAA Regional Climate Centers ACIS, 1991-2020 — Teton County
- Counties
- 14
- US Census TIGER/Line 2025
- Region type
- EPA ecoregion
- Growable Ground growing-region registry
Region boundary: Growable Ground growing-region registry — curated county clusters, EPA Level III ecoregions, and town clusters drawn finer than any county. The season figure is this region's own record, measured across its 14 member counties, not a state or national average.
Hardiness Zone Range
The Snake River Plain is not one growing season
One answer for the Snake River Plain averages 14 counties whose growing seasons are 72 days apart — from 133 frost-free days in Teton County to 205 in Canyon County. That is the same region, measured the same way, in the same years. Which end of it your land sits nearer decides what finishes before the first hard freeze.
The middle half of 14 counties runs 150–189 days, with a median of 170 days — a 72-day span end to end.
Measured across 14 member counties, each carrying its own 28°F normal. NOAA Regional Climate Centers ACIS, 1991-2020. A member with no own record is absent from the range rather than counted as zero — nothing here is interpolated to the region. Your own site sits somewhere inside this range; a parcel report resolves where.
Where the line runs inside the Snake River Plain
The middle half of the Snake River Plain runs 150–189 frost-free days, and 8 of its 14 counties sit outside that — 4 on the short side, 4 on the long. A regional planting date describes the middle well and the ends poorly, which is worth knowing before you follow one.
Under 150 frost-free days
4 counties
- Teton County · 133 days
- Clark County · 142 days
- Madison County · 144 days
3 of 4 shown
The end of the region that sets the planting calendar — start seed indoors here and the season stretches to meet the crop.
150–189 frost-free days
6 counties
0 of 6 shown
The middle half of the region, and the part a single regional season describes well.
Over 189 frost-free days
4 counties
- Canyon County · 205 days
- Ada County · 205 days
- Payette County · 201 days
3 of 4 shown
Long enough for a second succession of a quick crop after the first comes out.
Each county is placed by its OWN 28°F frost-free normal (NOAA Regional Climate Centers ACIS, 1991-2020), the same figure its own guide page publishes. Elevation, slope and cold-air drainage move a site within its county as well — which is the part only your address resolves.
What Grows in the Snake River Plain
All 1 of the plants below that publish a season requirement clear even Teton County’s 133 frost-free days — so on season alone, this grid works at both ends of the region. The 72-day spread still decides how far past this list you can push, and how early you can start.
Plants matched to the Snake River Plain's USDA zones 5a-7a, ordered by how much hardiness margin each has across the region — the ones with room to spare at both ends of this band lead. Each links to its full growing profile.
Native Plants of the Snake River Plain
Plants the USDA PLANTS Database documents as native and present in this region’s state, kept only where the published hardiness range meets the Snake River Plain’s USDA zones 5a-7a — closest range match first. Presence is recorded by state, so a plant can be documented across the state and still be scarce in your corner of the region.
The ground across the Snake River Plain
The USDA soil survey maps this ground county by county. These are those records weighted by land area across 14 member counties — this region’s own profile, not a state figure.
The ground is predominantly Aridisols, at 46% of mapped acres, followed by Mollisols (41%), Entisols (9%) and Inceptisols (2%). Eight soil orders appear somewhere inside the footprint, which is the honest reason a regional soil answer only goes so far. The most extensive named soils are Pancheri, Gem, and Power.
85% of those acres are well drained, and another 4% somewhat excessively drained, 3% somewhat poorly drained. Topsoil pH runs 6.1–8.2 between the lowest and the highest county on record.
Soil order
Aridisols
Drainage
Well drained
Topsoil pH
6.1–8.2
Hydric soils
1%
Soil changes across a driveway, so which of these your own ground sits on is a parcel question rather than a regional one. Teton County holds the most wetland ground here, at 11% — soil types explained.
USDA NRCS SSURGO via Soil Data Access
What this means for growing in the Snake River Plain
The soil survey reads this ground county by county, and the readings above are those records summed across the Snake River Plain. Here is what they mean for a garden here — and the move an experienced grower makes about each one.
Drainage
From county records85% of the mapped acres across the Snake River Plain are well drained — ground that drains quickly. That is area-weighted across all 14 of its mapped counties.
The upside is soil you can work early in spring and roots that never drown; the cost is that fast-draining ground dries out fast and leaches nutrients away before plants can use them.
Work in compost and mulch to hold moisture and feed, and water more often in short doses than deep and rarely.
USDA NRCS SSURGO
Surface pH
From county recordsTopsoil across the Snake River Plain runs pH 6.1–8.2 — near neutral in seven of its 14 counties.
This is the range most vegetables prefer — one correction you probably do not have to make, which is genuinely good news for a new bed.
Keep it there with compost rather than lime or sulfur, and only amend if your own soil test says otherwise.
USDA NRCS SSURGO
Safe to Grow Here?
What the federal record shows across the Snake River Plain — and how to grow with it.
Across the Snake River Plain's 14 counties the federal record holds 7,996 documented sites, mostly Nitrate (4,926), Underground Storage Tanks (2,006) and Brownfields (574). The heaviest single county is Ada County, with 2,791.
That is a regional count, not a reading of any one lot — proximity to a documented site is information, not a diagnosis. Open the map outlined to the Snake River Plain to see which records sit where you actually grow.
Sources Checked
Summed across the 14 counties in the Snake River Plain
A note from Gnorman
What an experienced grower watches for around here
In and around the Snake River Plain, two things run higher than the national average across the 14 counties in the Snake River Plain — Nitrate (4,926 sites) and CAFO (144 sites). That's not a problem with your land — it's information about it.
Nitrate: Nitrate contamination primarily comes from agricultural fertilizer runoff and failing septic systems.
CAFO: CAFOs pose a different contamination profile than chemical sources.
Test well water for nitrate if you rely on a private well for irrigation (EPA standard: 10 mg/L).
Wash all produce consumed raw thoroughly, especially leafy greens grown near CAFOs.
Sources: EPA, USGS — 1.8M documented sites tracked nationwide across 9 federal source types.
Your land is one point inside the Snake River Plain
Everything above resolves to the Snake River Plain as a whole — a footprint whose own counties record seasons 72 days apart, and hardiness across zones 5a-7a. Your parcel sits at one point in that range, not in the middle of it. Slope, tree cover, a low spot that pools cold air, and what is in the soil are all resolved at the address, and none of them are visible at region scale. That is the honest boundary of this page, and the reason the next step is a reading of your own ground rather than a better regional average.
Your Lot vs the Snake River Plain Average
Snake River Plain Average
- ●USDA Zones 5a-7a, averaged across Snake River Plain
- ●One soil character for all of Snake River Plain
- ●State-average frost dates
YOUR Parcel
- ✓Your exact zone, not Snake River Plain's 5a-7a
- ✓Your SSURGO soil type & pH
- ✓Your sun exposure, cast in 3D
See MY Growing Report
Read your parcel in the Snake River Plain
Pull a site-specific report for your exact address in the Snake River Plain — soil, sun, drainage, frost risk, contamination, and scored plant recommendations.
Three things about your lot that Snake River Plain averages can't show:
We read public map data around The Snake River Plain — soil, climate, flood, and parcel records. How we handle your address.
25+ data sources read at your address, not the Snake River Plain average
How we know this about the Snake River Plain
The boundary: an EPA Level III ecoregion (an area sharing climate, soils, and vegetation). Growing regions have no official boundary, so this footprint is our published one, and every figure on this page was measured over the counties inside it rather than borrowed from the state around it.
The datasets: hardiness from the USDA ARS Plant Hardiness Zone Map 2023, aggregated across the footprint; the growing season from NOAA Regional Climate Centers ACIS 1991–2020 28°F normals, read at each member’s own record; boundaries from US Census TIGER/Line 2025; the contamination record from the federal sources named in that beat above; the soil from the USDA NRCS SSURGO survey, read at each member county’s own record and weighted to this footprint by land area. Where a member carries no record of its own, it is absent from the figure rather than filled in.
Common questions about the Snake River Plain
What hardiness zone is the Snake River Plain?
The Snake River Plain spans USDA hardiness zones 5a-7a, aggregated from the USDA Agricultural Research Service Plant Hardiness Zone Map 2023 across the region's counties. Zones reflect average annual extreme minimum temperatures from 1991–2020 data.
How long is the growing season in the Snake River Plain?
Measured between 28°F hard freezes, the Snake River Plain's counties mostly run 150 to 189 frost-free days, median 170 (NOAA Regional Climate Centers ACIS, 1991–2020, over 14 member counties). That 39-day spread is the honest read — no single season describes 14 counties, and each county guide below carries its own.
When does frost risk end in the Snake River Plain?
Across the Snake River Plain, the middle half of member counties see their last 28°F hard freeze between Apr 18 and May 6 (median Apr 30), and their first fall freeze between Oct 4 and Oct 24. Those are hard freezes, not the last light frost: tender transplants wait for about May 21, and elevation decides which end of a 18-day spread you garden in.
What grows well in the Snake River Plain?
The Snake River Plain's conditions suit plants such as Potato, Lentil, Apple, Hop, Cherry. What actually thrives on any one site still turns on its specific soil, sun, and drainage — we score each plant against the real conditions at your address.
How is the Snake River Plain defined?
The Snake River Plain's footprint follows an EPA Level III ecoregion — a boundary drawn where climate, soils, and vegetation actually change rather than where a state line falls. It covers 14 counties, and the counties linked on this page are representative of the region, not an exhaustive list.
Which states does the Snake River Plain cover?
The Snake River Plain spans Idaho. Each state's full growing guide is linked on this page.
What other growing regions cover the same states?
Columbia Basin, Eastern Idaho (Upper Snake River Valley), Magic Valley, Idaho Panhandle (North Idaho), Treasure Valley, and Central Idaho Mountains share at least one state with the Snake River Plain. Growing regions overlap and interlock — a single address can sit inside more than one, which is why the precise read is always the parcel, not the region.
What this page reads at the Snake River Plain’s own scale
6 of the readings below were taken at the Snake River Plain's own scale — the zone 5a-7a band across its footprint, a median 170-day season across its 14 counties and 7,996 documented federal contamination records across its 14 counties, 2,791 of them in Ada County alone; one is borrowed from a wider read, named and linked below.
Measured here
- The USDA hardiness band 5a-7a aggregated across all 14 counties in the footprintUSDA PHZM 2023
- The boundary itself — the EPA Level III ecoregion its 14 counties sit inside, drawn where climate and soils changeEPA Level III Ecoregions
- The growing character that makes this region distinct from the states it crossesGrowable Ground subregion registry
- The 28°F season across the footprint — the middle half of its 14 counties run 150 to 189 frost-free days, median 170NOAA Regional Climate Centers ACIS, 1991-2020
- The federal contamination record over the whole footprint — 7,996 documented federal contamination records across its 14 counties, 2,791 of them in Ada County aloneEPA, USGS and USDA federal site records
- The soil order mix across the footprint — 46% Aridisols, topsoil pH 6.1–8.2, area-weighted across its 14 mapped countiesUSDA NRCS SSURGO
Inherited from a wider read
- The candidate plant list — its state's curated sets, merged and filtered to zones 5a-7afrom Idaho
What this page can’t tell you
- Which end of the 39-day range your ground sits at — 150 days at one extreme, 189 at the other, decided mostly by elevationfrost dates explained →
- Which of those soils your own ground sits on — the survey maps them county-wide, and they change across a drivewaysoil types explained →
- The soil pH, drainage, sun hours, and frost pockets on one specific lotwhy one lot differs from the next →
Explore the Snake River Plain
State growing guides
Representative counties
Other growing regions across Idaho
A dry basalt plateau of loess soils in the inland Northwest where irrigation turns arid ground into apple, cherry, hop, and wine-grape country.
Eastern Idaho's Upper Snake River Valley is the cold, high-elevation head of the same volcanic plain that gives Boise its 7a warmth — but here the growing reality inverts. At roughly 4,500–6,000 ft, Idaho Falls, Pocatello, and Rexburg sit in USDA zones 5a–5b with about 130–165 frost-free days at the population centers (shorter still in the outlying mountain valleys like Bear Lake and Caribou), running 1.5–2 zones colder and 40–70 days shorter than the Treasure Valley downstream. Routine late-May frosts make this short-season, cold-hardy, high-desert growing — the mirror image of the plain's warm western end that the broad Snake River Plain page averages away.
The irrigated heart of south-central Idaho, where Snake River canal water — the "magic" that turned high desert into cropland after the 1905 Milner Dam and the Carey Act land tracts — feeds a tight 6a–6b band on volcanic-ash soils at roughly 3,700 feet. Cooler and far more uniform than the wider Snake River Plain that runs from balmy Boise (7a) to the frosty eastern plain (5b), this is Idaho's dairy, sugar-beet, dry-edible-bean, and malting-barley heartland, with the Snake River Canyon and Shoshone Falls cutting straight through it.
Forested, lake-and-mountain far-north Idaho — nothing like the arid Snake River Plain or the treeless Palouse wheat prairie to the south. Big glacial lakes (Pend Oreille, Coeur d'Alene) buffer both spring frost and summer heat across a humid-continental, higher-precipitation belt of cedar-and-hemlock forest soils. Expect USDA zones 6a–6b and a cool, wet-spring season of roughly 148–187 frost-free days (verified county climate data), with last frosts into mid-May in the northern valleys — a short, moist window the southern-Idaho and Palouse pages can't describe.
Idaho's Boise-anchored growing corridor: the warm valley floor around Ada and Canyon counties reaches roughly 200 frost-free days at USDA zone 7a, while the Boise and Owyhee foothills that ring it run up to a full zone colder on a markedly shorter season.
Idaho's shortest growing season: the central Rockies high country runs just 94 frost-free days at Valley County (McCall), 104 at Custer (Stanley/Challis), and 110–117 across Idaho and Lemhi (Salmon) — a full 30–50 days shorter than the Wood River Valley one range south (Blaine, 143 days), with cold-air pooling that can drop frost into any summer month. At 4,000–6,500 ft in USDA 5a–6a, growers here lean on season extension, short-season and short-day varieties, and careful frost-pocket siting rather than fighting the calendar.