Monmouth, Oregon, sits in USDA hardiness zone 8b — room for a real mix of vegetables, fruit, and perennials matched to the local frost calendar.
The conditions favor cabbage, fig, california poppy, and collard greens, among others — though every individual site edits that list with its own soil, sun, and drainage.
Even in Monmouth, no two yards are alike.
A low spot, a south-facing slope, or a stand of trees moves the frost date and sun across a single Monmouth lot. 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 Monmouth — soil, climate, flood, and parcel records. How we handle your address.
No card required · your full report in seconds
Monmouth — the short answer
Monmouth, Oregon: USDA zone 8b, about 278 days between hard freezes, across 1K acres of city.
- USDA zone
- 8b
- USDA PHZM 2023
- Last hard freeze (28°F)
- Feb 25
- Polk County normal — NOAA 1991–2020, nearest to this town
- First hard freeze (28°F)
- Nov 30
- Polk County normal — NOAA 1991–2020, nearest to this town
- Days between freezes
- ~278
- Polk County normal — NOAA 1991–2020, nearest to this town
- City area
- 1K acres
- US Census TIGER/Line 2025
Every figure names the dataset it came from. No 30-year normal resolves at this town’s own centroid, so the hard-freeze dates are Polk County’s — the closest measured record, labelled as such rather than passed off as local.
Hardiness Zone Range
Zone 8b is Monmouth's average, not your lot's — a low corner or a tree line moves it. Against Monmouth's 278-day season, see what your own ground reads.
Soil varies lot by lot — soil types explained.
What this means for growing in Monmouth
Each reading below is measured for Monmouth itself — here is what it means for a garden here, and the move an experienced grower makes about it.
Season length
From county recordsMonmouth runs about 278 days between hard freezes (read from Polk County, the closest normal to Monmouth) — close to year-round growing.
Frost is rarely the limit here; winter plantings are as real as summer ones, and the harder question is which crops shrug off the summer heat.
Grow cool-season crops through the mild winter, and choose heat-tolerant varieties for the summer beds.
NOAA 1991–2020 Climate Normals
Winter hardiness
MeasuredMonmouth sits in USDA hardiness zone 8b.
The zone sets which perennials, shrubs, and fruit trees live through an average winter here — a plant rated for a colder zone is a safe bet, one rated warmer needs winter protection or gets treated as an annual.
Match perennials and fruit to the zone before you buy, so nothing you plant is a gamble against the cold.
USDA PHZM 2023
The kind of country Monmouth is in
Monmouth sits in the Willamette Valley — EPA Level III, inside the wider Marine West Coast Forest. That is read at Monmouth's own centroid rather than borrowed from Polk County.
What Grows in Monmouth
Every plant below cleared Monmouth's own zone 8b and its 278-day season. Each card opens that plant's Oregon profile. How we score.
Is it too late to plant in Monmouth?
Usually not — gardeners here simply switch what goes in the ground as the season moves. Cool-season crops can go in from around Jan 28; tender transplants wait until two to three weeks after the last 28°F hard freeze, which lands near Feb 25 (NOAA 1991–2020 climate normals); and from midsummer, planting counts back from the first fall freeze around Nov 30 — long-season crops need about 90 days of runway, quick greens only 30. And with a calendar this mild, the honest answer is that planting barely stops — winter opens seasons colder regions never see.
Documented around Monmouth
Survey cells within 31 miles of Monmouth checked for spotted lanternfly, none carrying a detection — a surveyed negative, not an absence of looking. Nearest documented record 493 miles off. What to watch for.
What's on the federal record near Monmouth
Closest first, within ~10 miles of Monmouth. Listing isn't leaking, and distance isn't exposure.
- TOPA MOBILUnderground Storage Tanks · 200 ft
- BOISE CASCADE REGION OFFICEUnderground Storage Tanks · 400 ft
- CHEVRON USA INC #99035Underground Storage Tanks · 950 ft
- JOSEPH FRANKO INCBrownfields · 950 ft
- JOSEPH FRANKO, INC.Underground Storage Tanks · 1000 ft
- BURGERVILLEBrownfields · 1000 ft
- SHELL - 507Underground Storage Tanks · 1100 ft
- BRANDT SANITARY SERVICE INCUnderground Storage Tanks · 1300 ft
- WESTERN OREGON STATE COLLEGEUnderground Storage Tanks · 1300 ft
- MAIN STREET PIZZAUnderground Storage Tanks · 1900 ft
- WESTERN OREGON UNIVERSITYBrownfields · 2300 ft
- WELL #1, WASTEWATER TREATMENT PLANTUnderground Storage Tanks · 2300 ft
6 more sites are on the record inside the same radius. See them on the map
Measured from Monmouth's center, not your beds. Run your own address for what's upwind of you specifically.
Environmental Intelligence
The counts behind that headline — every source type on the record near Monmouth.
Total Sites
252
within ~10 miles of Monmouth
Risk Level
Elevated
Highest-severity
2 Superfund sites (none NPL-listed)
Sources Checked
within ~10 miles of Monmouth
Severity Distribution
within ~10 miles of Monmouth
Highest-Severity Sites
A note from Gnorman
What an experienced grower watches for around here
In and around Monmouth, PFAS runs higher than the national average — 3 sites within ~10 miles of Monmouth. That's not a problem with your land — it's information about it.
PFAS: PFAS (per- and polyfluoroalkyl substances) are called "forever chemicals" because they do not biodegrade.
Test irrigation water source — this is the primary pathway for PFAS to reach garden crops.
Check your specific parcel in Monmouth
Get exact proximity distances to contamination sources for your specific parcel — plus soil, sun, drainage, and 1,086 plant recommendations.
25+ data sources read at your address, not the Monmouth average
Your land is one point inside Monmouth
Everything above resolves to Monmouth as a whole — one PHZM band, read across 1K acres, with hard-freeze dates borrowed from Polk County’s record because no 30-year normal resolves at this city’s own centroid. Your parcel is one point inside that footprint. 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 city 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 local average.
Your Lot vs the Monmouth Average
Monmouth Average
- ●USDA Zones 8b, averaged across Monmouth
- ●One soil character for all of Monmouth
- ●Frost dates read at Monmouth's scale: Feb 25 to Nov 30
YOUR Parcel
- ✓Your exact zone, not Monmouth's 8b
- ✓Your SSURGO soil type & pH
- ✓Your sun exposure, cast in 3D
See MY Growing Report
Read your specific parcel in Monmouth
Pull a site-specific report for your exact address in Monmouth, Oregon — soil, sun, drainage, frost risk, and scored plant recommendations.
Three things about your lot that Monmouth averages can't show:
We read public map data around Monmouth — soil, climate, flood, and parcel records. How we handle your address.
25+ data sources read at your address, not the Monmouth average
How we know this about Monmouth
The datasets: hardiness from the USDA ARS Plant Hardiness Zone Map 2023, read at this city’s own centroid; hard-freeze dates from NOAA 1991–2020 28°F normals at Polk County’s record, because none resolves here; boundaries and acreage from US Census TIGER/Line 2025; the contamination records from the federal sources named in their beats above. Soil is not read at city grain anywhere on this page — there is no city-resolution survey in our data, which is why you will find no soil grid here rather than a statewide one wearing a local label. The resolution ledger below names every figure this page inherited.
Common questions about Monmouth
When does frost risk typically end in Monmouth?
The last hard freeze (28°F) in Monmouth typically lands around Feb 25, per NOAA 1991–2020 climate normals — earlier than the light-frost dates most charts quote. That marks the hard freeze, not the last light frost — lighter frosts keep biting past it, which is why tender transplants here wait until about Mar 18.
When is the first frost in Monmouth?
The first hard freeze (28°F) in Monmouth typically arrives around Nov 30, per NOAA 1991–2020 climate normals — the point tender summer crops finish. Lighter frosts run ahead of it, near Nov 16, so the watching starts about Oct 31 — about 278 days after the spring freeze cleared.
How long is the growing season in Monmouth?
Measured between 28°F hard freezes, Monmouth sees about 278 frost-free days — roughly Feb 25 through Nov 30, per NOAA 1991–2020 climate normals. Tender crops work a shorter one: nearer Mar 18 to Nov 16, about 243 days.
Is the soil safe to grow vegetables in Monmouth?
The federal record around Monmouth is a meaningful one — 252 documented sites, mostly Underground Storage Tanks entries (130), the nearest Underground Storage Tanks record under a tenth of a mile out — 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.
How do I protect my plants from frost in Monmouth?
From about Oct 31 the job here turns from planting to protecting — the last start even a 30-day crop can finish. As the season closes around the first 28°F hard freeze near Nov 30 (NOAA 1991–2020 climate normals), three moves buy time: row cover or an old sheet over tender plants on still, clear nights; water the soil the afternoon before a freeze, so it holds warmth overnight; and harvest tomatoes, peppers and basil before Nov 30. Hardy greens and roots shrug off light frost and sweeten after it — leave them in.
Everything above is measured at Monmouth's scale — its 8b band and its 278-day season. Your yard writes its own version of Monmouth's numbers: we read soil, sun, drainage and frost at your exact address. Try it for 14 days — no card required.
What this page reads at Monmouth’s own scale
6 of the readings below were taken at Monmouth's own scale — the 1,433 acres it covers and 252 documented sites around it; 5 are borrowed from a wider read, named and linked below.
Measured here
- Monmouth's own USDA hardiness band, zones 8bUSDA PHZM 2023
- 252 documented contamination sites on the federal record near Monmouth, the closest Underground Storage Tanks record under a tenth of a mile out from the town centreFederal environmental registers
- Monmouth's boundary and the 1,433 acres inside itUS Census TIGER/Line 2025
- Which of 1,086 plants clear zones 8b and a ~278-day seasonGrowable Ground crop-matching engine
- The ecoregion at Monmouth's own centroid, the Willamette ValleyUS EPA Level III Ecoregions
- Lanternfly survey cells around Monmouth checked, none carrying a detectionlydemapr (De Bona & Helmus), 10 km survey lattice
Inherited from a wider read
- The 28°F hard-freeze dates — Monmouth has no normal of its own, so its county's is the closest measured readfrom Polk County
- Soil character — no town-scale survey exists, so Monmouth's 1,433 acres read through its county's SSURGO summaryfrom Polk County
- Growing-degree days and winter chill — measured county-wide only, so the county page carries themfrom Polk County
- The growing challenges every Oregon grower plans around — written at state scale, so they stay on the state guidefrom Oregon
- Butterfly and beetle records, and the farmland pesticide estimate — all published county-widefrom Polk County
What this page can’t tell you
- The soil pH, drainage, sun hours, and frost pockets on any one lot among Monmouth's 1,433 acreswhy one lot differs from the next →
- Which side of Monmouth you're on — a low spot frosts first and a south wall warms early, and one normal is being asked to speak for all 1,433 acresreading your own microclimate →
- How close that record sits to YOUR lot — the closest Underground Storage Tanks record under a tenth of a mile out, measured from the town centrehow we read the record →
- Where cold air settles, which slopes face the sun, and which way the wind runs on your own ground — measured at your address, and averaged away by any Monmouth-wide figureread your own land →