Whitman County, in Washington, sits in USDA hardiness zone 7a — a zone band wide enough that plant choice, not possibility, is the interesting question.
Expect apple, cherry, hop, and grape to be strong candidates here; the deciding factors on any one parcel stay local — soil, sun, and drainage.
Whitman County lies within the Palouse and the Columbia Basin — a regional growing area with its own character.
Grounded in USDA PHZM 2023 · Growable Ground suitability scoring · NOAA 1991–2020 Climate Normals
Whitman County holds more than one microclimate.
Soils and elevations shift across Whitman County, so your frost dates and drainage aren't the county average. Enter your address and we'll score 1,112 plants against your land's actual soil, sun, and frost.
We read public map data for this spot — soil, climate, flood, and parcel records. How we handle your address.
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Quick Facts
USDA Zones
7a
Last Hard Freeze (28°F)
Mar 15
County normal — light frosts run a few weeks later
First Hard Freeze (28°F)
Nov 12
County normal — light frosts arrive a few weeks earlier
County Area
1.4M acres
Hardiness Zone Range
Zone maps are averages across Whitman County. Your yard's slope, trees, and frost pockets shift what actually grows — see your land's exact reading.
Soil in Whitman County
Across Whitman County, the ground is predominantly Mollisols, where Palouse, Athena, and Walla Walla are the most extensive named soil series. The soil is generally well drained with a silt loam surface. Topsoil pH runs about 6.5–7.2, neutral. Rainfall drains through hydrologic group B soils.
Soil order
Mollisols
Drainage
Well drained
Prime farmland
6%
Hydric soils
1%
Soil still varies lot by lot — soil types explained.
What Grows in Whitman County
Plants matched to Whitman County's USDA zones 7a — each links to its full growing profile.
Is it too late to plant in Whitman County?
Rarely: the season closes in stages, not all at once, and each stage has its crops. Cool-season crops can go in from around Feb 15; tender transplants wait until two to three weeks after the last 28°F hard freeze, which lands near Mar 15 (NOAA 1991–2020 climate normals); and from midsummer, planting counts back from the first fall freeze around Nov 12 — long-season crops need about 90 days of runway, quick greens only 30. Here the season winds down slowly: late sowings, a real autumn harvest, and garlic in the ground before the first hard freeze.
Growing Challenges in Washington
What an experienced grower plans around here — each one has a move.
Extreme rain divide: 90+ inches west, 6 inches east of Cascades
Plant to your side of the Cascades, not to the state — your exact spot's rainfall decides the whole plan.
East side requires irrigation — no rain from June through September
With no summer rain, drip lines and deep mulch are the growing season — set them up before June.
Slug and root rot pressure on the wet west side
Raise the beds, bait the slugs, and water mornings only — the wet-side trio that keeps roots and leaves healthy; extension has the details.
Short seasons at elevation in the Cascades and northeast corners
In the short-season corners, fast varieties plus a cold frame or tunnel reliably close the gap.
For cultivar selection, pest pressure, and planting-time guidance specific to Washington, the WSU Extension is the authoritative local source.
Safe to Grow Here?
What the federal record shows across Whitman County — and how to grow with it.
We checked the federal record across Whitman County — 496 documented sites across 7 of the 9 source types we track.
The most significant on record: 1 Superfund site. Sites tracked in EPA's Superfund program — from assessment-stage CERCLIS entries to confirmed National Priorities List cleanup sites.
There's a meaningful federal record across Whitman County — worth a look before you plant food, not a reason to hold back from growing. Proximity to a documented site is information, not a diagnosis of any one yard. A soil test before new food beds is the sensible precaution here, and the map shows exactly which sites sit where, so you can see what's actually near you.
Sources: EPA, USGS — 1.8M documented sites tracked nationwide across 9 federal source types.
Environmental Intelligence
Understanding what's nearby helps you make informed decisions about where and how to grow.
Sources Checked
across Whitman County
Severity Distribution
across Whitman County
Highest-Severity Sites
A note from Gnorman
What an experienced grower watches for around here
In and around Whitman County, two things run higher than the national average — Nitrate (144 sites) and Underground Storage Tanks (307 sites). It's not cause for alarm — it's worth knowing, and there's a sensible way to grow around it.
Nitrate: Nitrate contamination primarily comes from agricultural fertilizer runoff and failing septic systems.
Underground Storage Tanks: Underground storage tanks are the single most common source of soil contamination near homes and gardens.
Test well water for nitrate if you rely on a private well for irrigation (EPA standard: 10 mg/L).
Use raised beds with imported soil — this eliminates the primary soil-contact pathway.
Check your specific parcel in Whitman County
Get exact proximity distances to contamination sources for your specific parcel — plus soil, sun, drainage, and 1,112 plant recommendations.
Three things about your exact spot that zone averages miss:
We read public map data for this spot — soil, climate, flood, and parcel records. How we handle your address.
25+ data sources analyzed in seconds
Your Specific Parcel Matters
Whitman County Average
- ●USDA Zones 7a
- ●Generic soil type for the area
- ●State-average frost dates
YOUR Parcel
- ✓Your exact hardiness zone
- ✓Your SSURGO soil type & pH
- ✓Your sun exposure, cast in 3D
See MY Growing Report
Read your parcel in Whitman County
Pull a site-specific report for your exact address in Whitman County, Washington — soil, sun, drainage, frost risk, and scored plant recommendations.
Three things about your exact spot that zone averages miss:
We read public map data for this spot — soil, climate, flood, and parcel records. How we handle your address.
25+ data sources analyzed in seconds
Key Growing Facts for Whitman County, Washington
- USDA Hardiness Zones: 7a (USDA PHZM 2023)
- Last Hard Freeze (28°F): Mar 15 (county normal, NOAA 1991–2020 Climate Normals — light frosts can follow for a few weeks)
- First Hard Freeze (28°F): Nov 12 (county normal, NOAA 1991–2020 Climate Normals — light frosts can arrive a few weeks earlier)
- Days Between Hard Freezes: ~242 (county normal, NOAA 1991–2020 Climate Normals)
- County Land Area: 1.4M acres (US Census TIGER 2025)
Zone data: USDA ARS Plant Hardiness Zone Map 2023. Climate data: NOAA NCEI. County boundaries: US Census TIGER/Line 2025.
Frost dates here are the Whitman County average. Low spots and tree cover move them by days on any one yard — see your exact frost windows.
Frequently Asked Questions
What hardiness zone is Whitman County, Washington?
Whitman County sits in USDA hardiness zone 7a, per the USDA Plant Hardiness Zone Map 2023. Zones reflect average annual extreme minimum temperatures from 1991–2020 weather data.
Is it too late to plant in Whitman County?
Rarely: the season closes in stages, not all at once, and each stage has its crops. Cool-season crops can go in from around Feb 15; tender transplants wait until two to three weeks after the last 28°F hard freeze, which lands near Mar 15 (NOAA 1991–2020 climate normals); and from midsummer, planting counts back from the first fall freeze around Nov 12 — long-season crops need about 90 days of runway, quick greens only 30. Here the season winds down slowly: late sowings, a real autumn harvest, and garlic in the ground before the first hard freeze.
When does frost risk typically end in Whitman County?
The last hard freeze (28°F) in Whitman County typically lands around Mar 15, per NOAA 1991–2020 climate normals — an earlier marker than the light-frost dates many planting charts quote. That marks the hard freeze, not the last light frost — light frosts can still bite for a few more weeks, so tender transplants usually wait another 2–3 weeks.
How long is the growing season in Whitman County?
Measured between 28°F hard freezes, Whitman County sees about 242 frost-free days — roughly Mar 15 through Nov 12, per NOAA 1991–2020 climate normals. Tender crops get a somewhat shorter practical window, since lighter frosts reach a few weeks past the hard-freeze dates on both ends.
What vegetables grow in Whitman County?
Whitman County's zone 7a supports a wide range — strong performers include Apple, Cherry, Hop, Grape, and Blueberry. What actually takes on any one site comes down to its soil, sun, and drainage, and we score each plant against the real conditions at your address.
Which hardiness zone is Whitman County, really?
Officially, Whitman County sits in USDA zone 7a (USDA PHZM 2023) — but a zone is a 30-year average of winter's coldest night across an area, and it can't see any one yard. A south-facing slope, a tree line, or a low frost pocket can shift a single site by half a zone either way, which is why neighboring gardeners often quote different numbers. We read the conditions at your exact address — soil, sun, slope, and frost — and score 1,112 plants against what's actually there.
Is the soil safe to grow vegetables in Whitman County?
The federal record around Whitman County is a meaningful one — 496 documented sites — so a soil test before new food beds is a sensible precaution here, not a reason to hold back from growing. Remember that proximity to a documented site is information, not a diagnosis of any one yard; the contamination map shows exactly what sits where.
Just moved to Whitman County — what should I know before planting?
Start with three facts. Whitman County sits in USDA zone 7a, which sets what survives winter; the last 28°F hard freeze typically clears around Mar 15, with about 242 frost-free days to work with (NOAA 1991–2020 climate normals); and 496 documented sites sit on the federal record here, so a soil test before food beds is the smart first step. From there, matching plants to your actual soil and sun is the fun part.
Everything on this page is a Whitman County average. Your yard writes its own version — we read soil, sun, drainage, and frost at your exact address. Try it for 14 days — no card required.
Will It Grow Here?
Zone fit is the first question — each answer below reads Washington's frost window, season length, and soil profile against the plant's real requirements.