The Willamette Valley spans USDA hardiness zones 8a-9a — enough range to grow cool-season vegetables, hardy fruit, and warm-season crops that mature before the first hard frost.
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. A short list that earns its place here — kale, douglas fir, garlic, and hazelnut — with any one site's soil, sun, and drainage making the final cut.
The Willamette Valley spans Oregon.
Your yard isn't all of the Willamette Valley.
The Willamette Valley spans USDA zones 8a-9a, 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 Willamette Valley — soil, climate, flood, and parcel records. How we handle your address.
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The Willamette Valley — the short answer
The Willamette Valley: USDA zones 8a-9a, 242–292 frost-free days depending where in it you stand, in Oregon.
- USDA zones
- 8a-9a
- USDA PHZM 2023, aggregated over the footprint
- Shortest season here
- 242 days
- NOAA Regional Climate Centers ACIS, 1991-2020 — Clackamas County
- Counties
- 9
- 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 9 member counties, not a state or national average.
Hardiness Zone Range
The Willamette Valley is not one growing season
One answer for the Willamette Valley averages 9 counties whose growing seasons are 50 days apart — from 242 frost-free days in Clackamas County to 292 in Multnomah 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 9 counties runs 256–284 days, with a median of 274 days — a 50-day span end to end.
Measured across 9 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 Willamette Valley
The middle half of the Willamette Valley runs 256–284 frost-free days, and 4 of its 9 counties sit outside that — 2 on the short side, 2 on the long. A regional planting date describes the middle well and the ends poorly, which is worth knowing before you follow one.
Under 256 frost-free days
2 counties
- Clackamas County · 242 days
- Marion County · 243 days
The end of the region that sets the planting calendar — start seed indoors here and the season stretches to meet the crop.
256–284 frost-free days
5 counties
0 of 5 shown
The middle half of the region, and the part a single regional season describes well.
Over 284 frost-free days
2 counties
- Multnomah County · 292 days
- Yamhill County · 290 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 Willamette Valley
Plants matched to the Willamette Valley's USDA zones 8a-9a, 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 Willamette Valley
Plants the USDA PLANTS Database documents as native and present in this region’s state, kept only where the published hardiness range meets the Willamette Valley’s USDA zones 8a-9a — 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 Willamette Valley
The USDA soil survey maps this ground county by county. These are those records weighted by land area across nine member counties — this region’s own profile, not a state figure.
The ground is predominantly Inceptisols, at 38% of mapped acres, followed by Mollisols (23%), Ultisols (23%) and Alfisols (8%). Nine 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 Bohannon, Klickitat, and Peavine.
71% of those acres are well drained, and another 11% moderately well drained, 8% poorly drained. Topsoil pH runs 5.1–6.1 between the lowest and the highest county on record. 17% of the footprint is classed prime farmland.
Soil order
Inceptisols
Drainage
Well drained
Topsoil pH
5.1–6.1
Hydric soils
9%
Soil changes across a driveway, so which of these your own ground sits on is a parcel question rather than a regional one. Linn County holds the most wetland ground here, at 16% — soil types explained.
USDA NRCS SSURGO via Soil Data Access
What this means for growing in the Willamette Valley
The soil survey reads this ground county by county, and the readings above are those records summed across the Willamette Valley. Here is what they mean for a garden here — and the move an experienced grower makes about each one.
Drainage
From county records71% of the mapped acres across the Willamette Valley are well drained — ground that drains quickly. That is area-weighted across all nine 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 Willamette Valley runs pH 5.1–6.1 — acidic in all nine of them.
Blueberries, potatoes, and rhododendrons thrive in it, but most vegetables start locking out nutrients below about pH 6.0 and grow pale and stunted no matter how much you feed them.
A measured lime application raises pH for the crops that need it — but test first, because the right rate depends on your own soil, not the county average.
USDA NRCS SSURGO
Safe to Grow Here?
What the federal record shows across the Willamette Valley — and how to grow with it.
Across the Willamette Valley's 9 counties the federal record holds 11,183 documented sites, mostly Underground Storage Tanks (6,204), Brownfields (3,348) and Toxics Release Inventory (632). The heaviest single county is Multnomah County, with 3,488.
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 Willamette Valley to see which records sit where you actually grow.
Sources Checked
Summed across the 9 counties in the Willamette Valley
A note from Gnorman
What an experienced grower watches for around here
In and around the Willamette Valley, Superfund runs higher than the national average — 140 sites across the 9 counties in the Willamette Valley. It's not cause for alarm — it's worth knowing, and there's a sensible way to grow around it.
Superfund: Superfund sites represent the most severe contamination in the federal system.
Commission professional soil testing before any food production (test for heavy metals, VOCs, and SVOCs).
Sources: EPA, USGS — 1.8M documented sites tracked nationwide across 9 federal source types.
Your land is one point inside the Willamette Valley
Everything above resolves to the Willamette Valley as a whole — a footprint whose own counties record seasons 50 days apart, and hardiness across zones 8a-9a. 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 Willamette Valley Average
Willamette Valley Average
- ●USDA Zones 8a-9a, averaged across Willamette Valley
- ●One soil character for all of Willamette Valley
- ●State-average frost dates
YOUR Parcel
- ✓Your exact zone, not Willamette Valley's 8a-9a
- ✓Your SSURGO soil type & pH
- ✓Your sun exposure, cast in 3D
See MY Growing Report
Read your parcel in the Willamette Valley
Pull a site-specific report for your exact address in the Willamette Valley — soil, sun, drainage, frost risk, contamination, and scored plant recommendations.
Three things about your lot that Willamette Valley averages can't show:
We read public map data around The Willamette Valley — soil, climate, flood, and parcel records. How we handle your address.
25+ data sources read at your address, not the Willamette Valley average
How we know this about the Willamette 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 Willamette Valley
What hardiness zone is the Willamette Valley?
The Willamette Valley spans USDA hardiness zones 8a-9a, 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 Willamette Valley?
Measured between 28°F hard freezes, the Willamette Valley's counties mostly run 256 to 284 frost-free days, median 274 (NOAA Regional Climate Centers ACIS, 1991–2020, over 9 member counties). That 28-day spread is the honest read — no single season describes 9 counties, and each county guide below carries its own.
When does frost risk end in the Willamette Valley?
Across the Willamette Valley, the middle half of member counties see their last 28°F hard freeze between Feb 17 and Mar 10 (median Feb 25), and their first fall freeze between Nov 22 and Nov 30. Those are hard freezes, not the last light frost: tender transplants wait for about Mar 18, and elevation decides which end of a 21-day spread you garden in.
What grows well in the Willamette Valley?
The Willamette Valley's conditions suit plants such as Kale, Douglas Fir, Garlic, Hazelnut, Grape (Pinot Noir), Blueberry. 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 Willamette Valley defined?
The Willamette Valley is defined here as a curated cluster of 9 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 Willamette Valley cover?
The Willamette Valley spans Oregon. Each state's full growing guide is linked on this page.
What other growing regions cover the same states?
Pacific Northwest, Columbia Basin, Oregon Coast (Maritime Cool-Summer Strip), Columbia Gorge, Northeast Oregon Mountain Valleys, and Central Oregon (High Desert) share at least one state with the Willamette 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 Willamette Valley’s own scale
6 of the readings below were taken at the Willamette Valley's own scale — the zone 8a-9a band across its footprint, a median 274-day season across its 9 counties and 11,183 documented federal contamination records across its 9 counties, 3,488 of them in Multnomah County alone; one is borrowed from a wider read, named and linked below.
Measured here
- The USDA hardiness band 8a-9a aggregated across all 9 counties in the footprintUSDA PHZM 2023
- The boundary itself — the 9 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 9 counties run 256 to 284 frost-free days, median 274NOAA Regional Climate Centers ACIS, 1991-2020
- The federal contamination record over the whole footprint — 11,183 documented federal contamination records across its 9 counties, 3,488 of them in Multnomah County aloneEPA, USGS and USDA federal site records
- The soil order mix across the footprint — 38% Inceptisols, topsoil pH 5.1–6.1, area-weighted across its 9 mapped countiesUSDA NRCS SSURGO
Inherited from a wider read
- The candidate plant list — its state's curated sets, merged and filtered to zones 8a-9afrom Oregon
What this page can’t tell you
- Which end of the 28-day range your ground sits at — 256 days at one extreme, 284 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 Willamette Valley
State growing guides
Counties in this region
Other growing regions across Oregon
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.
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.
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.
Unlike Oregon's mild westside valleys or the arid low Columbia Basin, Northeast Oregon's mountain valleys are a cold, high-elevation growing world — irrigated valley floors above 2,700 feet ringed by the Blue and Wallowa Mountains, where nightly cold-air pooling makes late-spring and early-fall frosts the defining constraint. Expect USDA zone 6b and a short ~150-165 frost-free-day season, a calendar that rewards short-season and cold-hardy crops, season extension, and careful frost timing over anything heat-loving.
Central Oregon is a cold, arid high-desert plateau east of the Cascade crest — a fundamentally different growing world from the mild Willamette Valley just over the mountains. Where valley gardens run a 240-290 day frost-free season in USDA zones 8-9, Bend, Redmond, Prineville, and Madras sit at roughly 3,000-3,600 ft in zones 6b-7a with only a ~150-175 day frost-free window, and a hard frost is possible in any month. Large day-to-night temperature swings and low humidity mean growers here plan around season extension — row cover, cold frames, hoop houses — rather than counting on long-season heat-lovers to ripen on their own.