The Palouse spans USDA hardiness zones 6b-7a — enough range to grow cool-season vegetables, hardy fruit, and warm-season crops that mature before the first hard frost.
Rolling loess hills of the inland Northwest with deep wind-deposited silt soils — classic dryland wheat, lentil, and pulse country. A short list that earns its place here — potato, lentil, kale, and garlic — with any one site's soil, sun, and drainage making the final cut.
The Palouse spans Idaho and Washington.
Your yard isn't all of the Palouse.
The Palouse spans USDA zones 6b-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 The Palouse — soil, climate, flood, and parcel records. How we handle your address.
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The Palouse — the short answer
The Palouse: USDA zones 6b-7a, 185–216 frost-free days depending where in it you stand, across 2 states.
- USDA zones
- 6b-7a
- USDA PHZM 2023, aggregated over the footprint
- Shortest season here
- 185 days
- NOAA Regional Climate Centers ACIS, 1991-2020 — Latah County
- Counties
- 3
- US Census TIGER/Line 2025
- Region type
- County cluster
- 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 3 member counties, not a state or national average.
Hardiness Zone Range
The Palouse is not one growing season
One answer for the Palouse averages 3 counties whose growing seasons are 31 days apart — from 185 frost-free days in Latah County to 216 in Nez Perce 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 3 counties runs 192–208 days, with a median of 199 days — a 31-day span end to end.
Measured across 3 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 Palouse
The middle half of the Palouse runs 192–208 frost-free days, and 2 of its 3 counties sit outside that — 1 on the short side, 1 on the long. A regional planting date describes the middle well and the ends poorly, which is worth knowing before you follow one.
Under 192 frost-free days
1 county
- Latah County · 185 days
The end of the region that sets the planting calendar — start seed indoors here and the season stretches to meet the crop.
192–208 frost-free days
1 county
0 of 1 shown
The middle half of the region, and the part a single regional season describes well.
Over 208 frost-free days
1 county
- Nez Perce County · 216 days
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 Palouse
All 1 of the plants below that publish a season requirement clear even Latah County’s 185 frost-free days — so on season alone, this grid works at both ends of the region. The 31-day spread still decides how far past this list you can push, and how early you can start.
Plants matched to the Palouse's USDA zones 6b-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 Palouse
Plants the USDA PLANTS Database documents as native and present in all 2 states this region crosses, kept only where the published hardiness range meets the Palouse’s USDA zones 6b-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 Palouse
The USDA soil survey maps this ground county by county. These are those records weighted by land area across three member counties — this region’s own profile, not a state figure.
The ground is predominantly Mollisols, at 81% of mapped acres, followed by Alfisols (9%), Andisols (7%) and Inceptisols (2%). Six 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 Palouse, Athena, and Walla Walla.
78% of those acres are well drained, and another 16% moderately well drained, 5% somewhat poorly drained. Topsoil pH runs 5.8–7.2 between the lowest and the highest county on record. 4% of the footprint is classed prime farmland.
Soil order
Mollisols
Drainage
Well drained
Topsoil pH
5.8–7.2
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. Whitman County holds the most wetland ground here, at 1% — soil types explained.
USDA NRCS SSURGO via Soil Data Access
What this means for growing in the Palouse
The soil survey reads this ground county by county, and the readings above are those records summed across the Palouse. Here is what they mean for a garden here — and the move an experienced grower makes about each one.
Drainage
From county records78% of the mapped acres across the Palouse are well drained — ground that drains quickly. That is area-weighted across all three 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 Palouse runs pH 5.8–7.2 — near neutral in all three of them.
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 Palouse — and how to grow with it.
Across the Palouse's 3 counties the federal record holds 1,129 documented sites, mostly Underground Storage Tanks (608), Nitrate (314) and Brownfields (110). The heaviest single county is Whitman County, with 496.
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 Palouse to see which records sit where you actually grow.
Sources Checked
Summed across the 3 counties in the Palouse
A note from Gnorman
What an experienced grower watches for around here
In and around the Palouse, two things run higher than the national average across the 3 counties in the Palouse — CAFO (14 sites) and Nitrate (314 sites). Knowing it is half the work — and it's nothing a thoughtful grower can't plan for.
CAFO: CAFOs pose a different contamination profile than chemical sources.
Nitrate: Nitrate contamination primarily comes from agricultural fertilizer runoff and failing septic systems.
Wash all produce consumed raw thoroughly, especially leafy greens grown near CAFOs.
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.
Your land is one point inside the Palouse
Everything above resolves to the Palouse as a whole — a footprint whose own counties record seasons 31 days apart, and hardiness across zones 6b-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 Palouse Average
Palouse Average
- ●USDA Zones 6b-7a, averaged across Palouse
- ●One soil character for all of Palouse
- ●State-average frost dates
YOUR Parcel
- ✓Your exact zone, not Palouse's 6b-7a
- ✓Your SSURGO soil type & pH
- ✓Your sun exposure, cast in 3D
See MY Growing Report
Read your parcel in the Palouse
Pull a site-specific report for your exact address in the Palouse — soil, sun, drainage, frost risk, contamination, and scored plant recommendations.
Three things about your lot that Palouse averages can't show:
We read public map data around The Palouse — soil, climate, flood, and parcel records. How we handle your address.
25+ data sources read at your address, not the Palouse average
How we know this about the Palouse
The boundary: a cluster of neighboring counties. 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 Palouse
What hardiness zone is the Palouse?
The Palouse spans USDA hardiness zones 6b-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 Palouse?
Measured between 28°F hard freezes, the Palouse's counties mostly run 192 to 208 frost-free days, median 199 (NOAA Regional Climate Centers ACIS, 1991–2020, over 3 member counties). That 16-day spread is the honest read — no single season describes 3 counties, and each county guide below carries its own.
When does frost risk end in the Palouse?
Across the Palouse, the middle half of member counties see their last 28°F hard freeze between Apr 5 and Apr 15 (median Apr 8), and their first fall freeze between Oct 24 and Oct 29. Those are hard freezes, not the last light frost: tender transplants wait for about Apr 29, and elevation decides which end of a 10-day spread you garden in.
What grows well in the Palouse?
The Palouse's conditions suit plants such as Potato, Lentil, Kale, Garlic, Western Red Cedar, Apple. 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 Palouse defined?
The Palouse is defined here as a curated cluster of 3 neighboring counties that share a growing character. Growing regions have no official boundary, so this footprint is our published one — every county in it is named on this page.
Which states does the Palouse cover?
The Palouse spans Idaho and Washington. Each state's full growing guide is linked on this page.
What other growing regions cover the same states?
Pacific Northwest, Columbia Basin, Snake River Plain, Eastern Idaho (Upper Snake River Valley), Magic Valley, and Idaho Panhandle (North Idaho) share at least one state with the Palouse. 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 Palouse’s own scale
6 of the readings below were taken at the Palouse's own scale — the zone 6b-7a band across its footprint, a median 199-day season across its 3 counties and 1,129 documented federal contamination records across its 3 counties, 496 of them in Whitman County alone; one is borrowed from a wider read, named and linked below.
Measured here
- The USDA hardiness band 6b-7a aggregated across all 3 counties in the footprintUSDA PHZM 2023
- The boundary itself — the 3 counties this region is curated fromGrowable Ground subregion registry
- 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 3 counties run 192 to 208 frost-free days, median 199NOAA Regional Climate Centers ACIS, 1991-2020
- The federal contamination record over the whole footprint — 1,129 documented federal contamination records across its 3 counties, 496 of them in Whitman County aloneEPA, USGS and USDA federal site records
- The soil order mix across the footprint — 81% Mollisols, topsoil pH 5.8–7.2, area-weighted across its 3 mapped countiesUSDA NRCS SSURGO
Inherited from a wider read
- The candidate plant list — all 2 member states' curated sets, merged and filtered to zones 6b-7afrom Idaho and Washington
What this page can’t tell you
- Which end of the 16-day range your ground sits at — 192 days at one extreme, 208 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 Palouse
State growing guides
Counties in this region
Other growing regions across Idaho and Washington
The maritime Northwest west of the Cascade crest — mild, wet winters and dry summers behind berries, tree fruit, and lush cool-season gardens. (Union of the west-side ecoregions.)
A dry basalt plateau of loess soils in the inland Northwest where irrigation turns arid ground into apple, cherry, hop, and wine-grape country.
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.
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.