Multnomah County, in Oregon, sits in USDA hardiness zone 9a — a range where zone-matched perennials and frost-aware annual timing set what succeeds.
On paper, hazelnut, grape (pinot noir), kale, and douglas fir all suit these conditions — on the ground, soil, sun, and drainage make the final call.
Multnomah County lies within the Willamette Valley and the Pacific Northwest — a regional growing area with its own character.
Grounded in USDA PHZM 2023 · Growable Ground suitability scoring
Multnomah County holds more than one microclimate.
Soils and elevations shift across Multnomah 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
9a
Last Frost (state avg.)
Mar 1 - Jun 15
First Frost (state avg.)
Sep 1 - Nov 15
County Area
276K acres
Hardiness Zone Range
Growing Season
Zone maps are averages across Multnomah County. Your yard's slope, trees, and frost pockets shift what actually grows — see your land's exact reading.
Soil in Multnomah County
Across Multnomah County, the ground is predominantly Inceptisols, where Zygore, Cascade, and Goble are the most extensive named soil series. The soil is generally well drained with a silt loam surface. Topsoil pH runs about 5.6–5.8, moderately acidic. Rainfall drains through hydrologic group B soils.
Soil order
Inceptisols
Drainage
Well drained
Prime farmland
6%
Hydric soils
14%
Soil still varies lot by lot — soil types explained.
What Grows in Multnomah County
Plants matched to Multnomah County's USDA zones 9a — each links to its full growing profile.
Growing Challenges in Oregon
What an experienced grower plans around here — each one has a move.
West side: excessive rain and overcast skies reduce sun for warm-season crops
Map your sun honestly — a south-facing bed against a light wall recovers a surprising amount of the light the clouds take.
East side: arid conditions (8-15 inches rainfall) require irrigation
East of the Cascades, drip irrigation is infrastructure, not an accessory — plan it before the first planting.
Slug pressure is extreme in western Oregon
Evening patrols, iron-phosphate baits, and dry mulch edges knock slugs back — your extension guide covers the full toolkit.
Mountain areas have very short seasons (60-90 frost-free days)
At 60-90 frost-free days, season extension is the difference between a garden and a gamble — a high tunnel changes the math.
For cultivar selection, pest pressure, and planting-time guidance specific to Oregon, the OSU Extension Service is the authoritative local source.
Safe to Grow Here?
What the federal record shows across Multnomah County — and how to grow with it.
We checked the federal record across Multnomah County — 3,488 documented sites across 8 of the 9 source types we track.
The most significant on record: 58 Superfund sites. Sites tracked in EPA's Superfund program — from assessment-stage CERCLIS entries to confirmed National Priorities List cleanup sites.
Multnomah County carries one of the heavier federal records we track — and that's not a verdict on your yard. Proximity to a documented site is information, not a diagnosis: nothing here says any particular parcel is affected. It does earn one concrete step — before food beds go in the ground, a professional soil test tells you exactly what you're working with, and raised beds with clean imported soil grow well almost anywhere in the meantime.
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.
Severity Distribution
across Multnomah County
Highest-Severity Sites
A note from Gnorman
What an experienced grower watches for around here
In and around Multnomah County, Superfund runs higher than the national average — 58 sites nearby. Knowing it is half the work — and it's nothing a thoughtful grower can't plan for.
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).
Check your specific parcel in Multnomah 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
Multnomah County Average
- ●USDA Zones 9a
- ●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 Multnomah County
Pull a site-specific report for your exact address in Multnomah County, Oregon — 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 Multnomah County, Oregon
- USDA Hardiness Zones: 9a (USDA PHZM 2023)
- Last Spring Frost (state avg.): Mar 1 - Jun 15 (NOAA 30-Year Climate Normals)
- First Fall Frost (state avg.): Sep 1 - Nov 15 (NOAA 30-Year Climate Normals)
- County Land Area: 276K 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 Multnomah 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 Multnomah County, Oregon?
Multnomah County sits in USDA hardiness zone 9a, per the USDA Plant Hardiness Zone Map 2023. Zones reflect average annual extreme minimum temperatures from 1991–2020 weather data.
When does frost risk typically end in Multnomah County?
Multnomah County follows Oregon's statewide frost window: last spring frost around Mar 1 - Jun 15 and first fall frost around Sep 1 - Nov 15, per NOAA 30-year climate normals (1991–2020). Frost dates shift with elevation and local microclimate, so watch your own site's cold pockets.
What vegetables grow in Multnomah County?
Multnomah County's zone 9a supports a wide range — strong performers include Hazelnut, Grape (Pinot Noir), Kale, Douglas Fir, and Garlic. 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 Multnomah County, really?
Officially, Multnomah County sits in USDA zone 9a (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 Multnomah County?
The federal record around Multnomah County runs heavier than most — 3,488 documented sites — so test the soil before planting food in the ground, and raised beds with clean imported soil grow well in the meantime. Even here, proximity to a documented site is information, not a diagnosis of any one yard; the contamination map shows exactly what's recorded and where.
Just moved to Multnomah County — what should I know before planting?
Start with three facts. Multnomah County sits in USDA zone 9a, which sets what survives winter; the statewide frost window runs about Mar 1 - Jun 15 to Sep 1 - Nov 15 (NOAA 30-year climate normals); and 3,488 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 Multnomah 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 Oregon's frost window, season length, and soil profile against the plant's real requirements.