The Walla Walla Valley spans USDA hardiness zone 7a — a zone band wide enough that plant choice, not possibility, is the interesting question.
Expect kale, potato, douglas fir, and garlic to be strong candidates here; the deciding factors on any one parcel stay local — soil, sun, and drainage.
The Walla Walla Valley spans Oregon and Washington.
Your yard isn't all of the Walla Walla Valley.
The Walla Walla Valley spans USDA zones 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 Walla Walla Valley — soil, climate, flood, and parcel records. How we handle your address.
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The Walla Walla Valley — the short answer
The Walla Walla Valley: USDA zones 7a, 208–222 frost-free days, across 2 states.
- USDA zones
- 7a
- USDA PHZM 2023, aggregated over the footprint
- Frost-free season
- 208–222 days
- NOAA Regional Climate Centers ACIS, 1991-2020
- Counties
- 2
- 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. Where a region publishes no measured season, no season figure is shown.
Hardiness Zone Range
What Grows in the Walla Walla Valley
Plants matched to the Walla Walla Valley's USDA zones 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 Walla Walla Valley
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 Walla Walla Valley’s USDA zones 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 Walla Walla Valley
The USDA soil survey maps this ground county by county. These are those records weighted by land area across two member counties — this region’s own profile, not a state figure.
The ground is predominantly Mollisols, at 65% of mapped acres, followed by Andisols (21%), Aridisols (5%) and Inceptisols (4%). Seven 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 Walla Walla, Ritzville, and Limberjim.
92% of those acres are well drained, and another 3% excessively drained, 1% moderately well drained. Topsoil pH runs 6.5–7.2 between the lowest and the highest county on record. 3% of the footprint is classed prime farmland.
Soil order
Mollisols
Drainage
Well drained
Topsoil pH
6.5–7.2
Hydric soils
0%
Soil changes across a driveway, so which of these your own ground sits on is a parcel question rather than a regional one. Umatilla 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 Walla Walla Valley
The soil survey reads this ground county by county, and the readings above are those records summed across the Walla Walla Valley. Here is what they mean for a garden here — and the move an experienced grower makes about each one.
Drainage
From county records92% of the mapped acres across the Walla Walla Valley are well drained — ground that drains quickly. That is area-weighted across all two 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 Walla Walla Valley runs pH 6.5–7.2 — near neutral in all two 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 Walla Walla Valley — and how to grow with it.
Across the Walla Walla Valley's 2 counties the federal record holds 1,018 documented sites, mostly Underground Storage Tanks (660), Nitrate (154) and Brownfields (133). The heaviest single county is Umatilla County, with 608.
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 Walla Walla Valley to see which records sit where you actually grow.
Sources Checked
Summed across the 2 counties in the Walla Walla Valley
A note from Gnorman
What an experienced grower watches for around here
In and around the Walla Walla Valley, two things run higher than the national average across the 2 counties in the Walla Walla Valley — CAFO (16 sites) and Underground Storage Tanks (660 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.
Underground Storage Tanks: Underground storage tanks are the single most common source of soil contamination near homes and gardens.
Wash all produce consumed raw thoroughly, especially leafy greens grown near CAFOs.
Use raised beds with imported soil — this eliminates the primary soil-contact pathway.
Sources: EPA, USGS — 1.8M documented sites tracked nationwide across 9 federal source types.
Your land is one point inside the Walla Walla Valley
Everything above resolves to the Walla Walla Valley as a whole — a footprint spanning USDA zones 7a. Your parcel sits in exactly one of them. 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 Walla Walla Valley Average
Walla Walla Valley Average
- ●USDA Zones 7a, averaged across Walla Walla Valley
- ●One soil character for all of Walla Walla Valley
- ●State-average frost dates
YOUR Parcel
- ✓Your exact zone, not Walla Walla Valley's 7a
- ✓Your SSURGO soil type & pH
- ✓Your sun exposure, cast in 3D
See MY Growing Report
Read your parcel in the Walla Walla Valley
Pull a site-specific report for your exact address in the Walla Walla Valley — soil, sun, drainage, frost risk, contamination, and scored plant recommendations.
Three things about your lot that Walla Walla Valley averages can't show:
We read public map data around The Walla Walla Valley — soil, climate, flood, and parcel records. How we handle your address.
25+ data sources read at your address, not the Walla Walla Valley average
How we know this about the Walla Walla Valley
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 Walla Walla Valley
What hardiness zone is the Walla Walla Valley?
The Walla Walla Valley spans USDA hardiness zones 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 Walla Walla Valley?
Measured between 28°F hard freezes, the Walla Walla Valley's counties mostly run 212 to 219 frost-free days, median 215 (NOAA Regional Climate Centers ACIS, 1991–2020, over 2 member counties). That 7-day spread is the honest read — no single season describes 2 counties, and each county guide below carries its own.
When does frost risk end in the Walla Walla Valley?
Across the Walla Walla Valley, the middle half of member counties see their last 28°F hard freeze between Mar 28 and Apr 1 (median Mar 30), and their first fall freeze between Oct 30 and Nov 2. Those are hard freezes, not the last light frost: tender transplants wait for about Apr 20, and elevation decides which end of a 4-day spread you garden in.
What grows well in the Walla Walla Valley?
The Walla Walla Valley's conditions suit plants such as Kale, Potato, Douglas Fir, Garlic, Western Red Cedar, Hazelnut. 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 Walla Walla Valley defined?
The Walla Walla Valley is defined here as a curated cluster of 2 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 Walla Walla Valley cover?
The Walla Walla Valley spans Oregon 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, Willamette Valley, Oregon Coast (Maritime Cool-Summer Strip), Puget Sound Lowlands, and Columbia Gorge share at least one state with the Walla Walla Valley. 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 Walla Walla Valley’s own scale
5 of the readings below were taken at the Walla Walla Valley's own scale — the zone 7a band across its footprint, a median 215-day season across its 2 counties and 1,018 documented federal contamination records across its 2 counties, 608 of them in Umatilla County alone; one is borrowed from a wider read, named and linked below.
Measured here
- The USDA hardiness band 7a aggregated across all 2 counties in the footprintUSDA PHZM 2023
- The boundary itself — the 2 counties this region is curated fromGrowable Ground subregion registry
- The 28°F season across the footprint — the middle half of its 2 counties run 212 to 219 frost-free days, median 215NOAA Regional Climate Centers ACIS, 1991-2020
- The federal contamination record over the whole footprint — 1,018 documented federal contamination records across its 2 counties, 608 of them in Umatilla County aloneEPA, USGS and USDA federal site records
- The soil order mix across the footprint — 65% Mollisols, topsoil pH 6.5–7.2, area-weighted across its 2 mapped countiesUSDA NRCS SSURGO
Inherited from a wider read
- The candidate plant list — all 2 member states' curated sets, merged and filtered to zones 7afrom Oregon and Washington
What this page can’t tell you
- Which end of the 7-day range your ground sits at — 212 days at one extreme, 219 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 Walla Walla Valley
State growing guides
Counties in this region
Other growing regions across Oregon 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.
Oregon's broad maritime valley pairs deep alluvial soils with cool wet winters and dry summers — the heart of the state's hazelnut, berry, and Pinot country.
Unlike the inland Willamette Valley captured by the broad Pacific Northwest region, the Oregon coast runs the opposite constraint: persistent marine fog holds summer heat so low that tomatoes, peppers, melons, and sweet corn rarely ripen — yet the same maritime air delivers a 263–308-day frost-free season (per county_data.json) where brassicas, greens, and other cool-season crops thrive nearly year-round. Curry County's south-coast banana belt around Brookings (zone 9b, the mildest winters in Oregon) anchors the U.S. Easter lily bulb district. Lead a coastal grower to plan for cool-season abundance and short-season or greenhouse strategies for heat-lovers — not the inland valley's frost-limited but heat-rich pattern.
The maritime lowland ringing Puget Sound — EPA's Puget Lowland ecoregion across Island, Kitsap, Mason, San Juan, and Thurston counties — where mild marine winters hold USDA zones 8a-9a and a long 227-to-300-day frost-free season.
A river canyon cut through the Cascades where wet marine air gives way to high desert in forty miles — pear, cherry, and apple orchards at the west end, vineyards and dryland ground at the east.