Mendocino County, in California, sits in USDA hardiness zone 9a — a band that supports both cool-season staples and warm-season crops chosen to fit the local frost window.
Crops well matched to these conditions include artichoke, fig, california poppy, and cabbage — though what thrives on any one site still turns on its specific soil, sun, and drainage.
Mendocino County lies within the Mendocino / Anderson Valley and the Pacific Northwest — a regional growing area with its own character.
Grounded in USDA PHZM 2023 · Growable Ground suitability scoring · NOAA 1991–2020 Climate Normals
Mendocino County holds more than one microclimate.
Soils and elevations shift across Mendocino County, so your frost dates and drainage aren't the county average. 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 Mendocino County — soil, climate, flood, and parcel records. How we handle your address.
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Mendocino County — the short answer
Mendocino County, California: USDA zone 9a, about 304 days between hard freezes, across 2.2M acres.
- USDA zone
- 9a
- USDA PHZM 2023
- Last hard freeze (28°F)
- Feb 5
- NOAA 1991–2020 Climate Normals, 28°F
- First hard freeze (28°F)
- Dec 6
- NOAA 1991–2020 Climate Normals, 28°F
- Days between freezes
- ~304
- NOAA 1991–2020 Climate Normals, 28°F
- County area
- 2.2M acres
- US Census TIGER/Line 2025
Every figure names the dataset it came from. Hard-freeze dates are county 28°F normals: light frosts run a few weeks past them, and tender transplants usually wait 2–3 weeks after the last hard freeze.
Hardiness Zone Range
Zone 9a is Mendocino County's average, not your lot's — a low corner or a tree line moves it. Against Mendocino County's 304-day season, see what your own ground reads.
Heat and winter chill in Mendocino County
Across a year, Mendocino County accumulates about 2,742 growing degree days above 50°F, about 1,015 fewer than the middle California county — ahead of 14 of California’s 57 counties. Degree days are the heat a crop actually gets to work with — more of them is more room to ripen a long-season crop before the freeze closes the window.
Winter banks about 1,840 hours below 45°F, 653 more than the California middle of 1,187. Chill is what tells a fruit tree its dormancy is over, and it is set by climate rather than by anything you can build.
Grounded in PRISM Climate Group, Oregon State University — 1991–2020 monthly normals
Soil in Mendocino County
Across Mendocino County, the ground is predominantly Alfisols, where Ornbaun, Hopland, and Yorkville are the most extensive named soil series. The soil is generally well drained with a loam surface. Topsoil pH runs about 5.8–6.3, moderately acidic. Rainfall drains through hydrologic group C soils.
Soil order
Alfisols
Drainage
Well drained
Hydric soils
2%
Soil still varies lot by lot — soil types explained.
How the ground varies across Mendocino County
The USDA soil survey maps 78% of Mendocino County as well drained — but another 20% drains differently: 9% somewhat excessively drained, 5% moderately well drained.
Ornbaun is the most extensive named soil at 6% of mapped acres, then Hopland (6%) and Yorkville (5%).
Which of them your own lot sits on is a parcel question, not a county one. Check your address for the survey at your boundary.
What this means for growing in Mendocino County
Each reading below is measured for Mendocino County itself — here is what it means for a garden here, and the move an experienced grower makes about it.
Drainage
MeasuredThe dominant soils across Mendocino County are well drained, in hydrologic group C — ground that drains quickly.
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
MeasuredTopsoil across Mendocino County runs about pH 5.8–6.3, close to neutral.
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
Season length
MeasuredMendocino County runs about 304 days between hard freezes — 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
MeasuredMendocino County sits in USDA hardiness zone 9a.
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 Mendocino County is in
Mendocino County spans 3 EPA Level III ecoregions — Klamath Mountains/California High North Coast Range (44%), Coast Range (43%) and Central California Foothills and Coastal Mountains (14%). Which one your land falls in changes what grows wild there and how the ground behaves, and a county-wide answer cannot tell you which.
What Grows in Mendocino County
We scored all 1,086 plants against Mendocino County's own USDA zone 9a and its own 304-day season between hard freezes, using the same matching engine that runs a full parcel report. These cleared both. Sun, soil pH and drainage vary lot by lot — those are the parcel questions below. Each card opens that plant's California profile.
Is it too late to plant in Mendocino County?
Usually not — gardeners here simply switch what goes in the ground as the season moves. Cool-season crops can go in from around Jan 8; tender transplants wait until two to three weeks after the last 28°F hard freeze, which lands near Feb 5 (NOAA 1991–2020 climate normals); and from midsummer, planting counts back from the first fall freeze around Dec 6 — long-season crops need about 90 days of runway, quick greens only 30. With almost year-round growing weather, timing is about heat and rainfall more than frost — some bench is always in play.
Documented around Mendocino County
- monarch butterfly15 documented records
Sighting records, so they follow observers as much as insects.
What gets applied to farmland in Mendocino County
USGS estimates 15,767 lb of Glyphosate on Mendocino County farmland in 2019, its largest by weight, ahead of Cyprodinil (1,160 lb) and Boscalid (629 lb).
Farmland across the whole county, not any one lot. Check your address for the site-by-site record.
Safe to Grow Here?
What the federal record shows across Mendocino County — and how to grow with it.
We checked the federal record across Mendocino County — 787 documented sites across 7 of the 9 source types we track.
The most significant on record: 8 Superfund sites. 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 Mendocino 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.
What's on the federal record near Mendocino County
Closest first, across Mendocino County. Listing isn't leaking, and distance isn't exposure.
- MENDOCINO SOLID WASTE MANAGEMENT AUTHORITYBrownfields · 3.1 mi
- CHARLIE’S MOBILE AUTO WORKSBrownfields · 3.6 mi
- CUTTER LUMBER CO.Brownfields · 3.7 mi
- CHRIS LAND TRUCKINGBrownfields · 4.5 mi
- BUD GARMAN CONSTRUCTION SERVICES INCBrownfields · 4.6 mi
- VEGAN BUDDHA LLCBrownfields · 4.7 mi
- MENDOCINO SOLID WASTE MANAGEMENT AUTHBrownfields · 4.8 mi
- WILLITS SOLID WASTE TRANSFER & RECYCLINGBrownfields · 4.8 mi
- North Willits PatriotUnderground Storage Tanks · 4.8 mi
- PATRIOT GAS MARTBrownfields · 4.8 mi
- WILLITS UNIFIED SCHOOL DISTRICTBrownfields · 4.8 mi
- Village Market 2Underground Storage Tanks · 4.8 mi
6 more sites are on the record inside the same radius. See them on the map
Measured from Mendocino County'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 Mendocino County.
Sources Checked
across Mendocino County
Severity Distribution
across Mendocino County
Highest-Severity Sites
A note from Gnorman
What an experienced grower watches for around here
In and around Mendocino County, two things run higher than the national average across Mendocino County — Brownfields (568 sites) and Mining (52 sites). Knowing it is half the work — and it's nothing a thoughtful grower can't plan for.
Brownfields: Brownfield sites are former commercial or industrial properties where legacy soil contamination (heavy metals, PAHs, petroleum compounds) may persist.
Mining: Mining sites — both historic and active — can leach heavy metals (arsenic, lead, cadmium, mercury) into soil and water for centuries after operations cease.
Check EPA brownfield remediation status — many sites have completed cleanup with institutional controls.
Test soil for heavy metals (lead, arsenic, cadmium, mercury) — this is essential near any mining site.
Check your specific parcel in Mendocino County
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 Mendocino County average
Your land is one point inside Mendocino County
Everything above resolves to Mendocino County as a whole — one PHZM band and one county frost record, read across 2.2M acres. 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 county 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 county average.
Your Lot vs the Mendocino County Average
Mendocino County Average
- ●USDA Zones 9a, averaged across Mendocino County
- ●One soil character for all of Mendocino County
- ●Frost dates read at Mendocino County's scale: Feb 5 to Dec 6
YOUR Parcel
- ✓Your exact zone, not Mendocino County's 9a
- ✓Your SSURGO soil type & pH
- ✓Your sun exposure, cast in 3D
See MY Growing Report
Read your parcel in Mendocino County
Pull a site-specific report for your exact address in Mendocino County, California — soil, sun, drainage, frost risk, and scored plant recommendations.
Three things about your lot that Mendocino County averages can't show:
We read public map data around Mendocino County — soil, climate, flood, and parcel records. How we handle your address.
25+ data sources read at your address, not the Mendocino County average
How we know this about Mendocino County
The datasets: hardiness from the USDA ARS Plant Hardiness Zone Map 2023, read at county grain; hard-freeze dates from NOAA 1991–2020 28°F normals at this county’s own record where one resolves, and the labelled statewide window where none does; soils from the USDA NRCS SSURGO survey, area-weighted across the county’s own map units; boundaries and acreage from US Census TIGER/Line 2025; the contamination and pesticide records from the federal sources named in their beats above. Where Mendocino County carries no record of its own, the figure is inherited and labelled — the resolution ledger below names each.
Common questions about Mendocino County
When does frost risk typically end in Mendocino County?
The last hard freeze (28°F) in Mendocino County typically lands around Feb 5, 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 Feb 26.
How long is the growing season in Mendocino County?
Measured between 28°F hard freezes, Mendocino County sees about 304 frost-free days — roughly Feb 5 through Dec 6, per NOAA 1991–2020 climate normals. Tender crops work a shorter one: nearer Feb 26 to Nov 22, about 269 days.
Is the soil safe to grow vegetables in Mendocino County?
The federal record around Mendocino County is a meaningful one — 787 documented sites, mostly Brownfields entries (568), the nearest Brownfields record about 3.1 miles 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.
Everything above is measured at Mendocino County's scale — its 9a band and its 304-day season. Your yard writes its own version of Mendocino County's numbers: 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 California's frost window, season length, and soil profile against the plant's real requirements.
What this page reads at Mendocino County’s own scale
9 of the readings below were taken at Mendocino County's own scale — its own ~304-day span between 28°F freezes, the 3 most extensive soil series mapped here and 787 documented sites inside its boundary; one is borrowed from a wider read, named and linked below.
Measured here
- Mendocino County's own USDA hardiness band, zones 9aUSDA PHZM 2023
- Mendocino County's own 28°F hard-freeze dates and its ~304-day span between themNOAA 1991–2020 Climate Normals
- The soil order, drainage, surface pH, and the 3 most extensive named soil series mapped in Mendocino CountyUSDA NRCS SSURGO
- 787 documented contamination sites inside the county boundary, distance-sorted from its center — the closest Brownfields record about 3.1 miles outFederal environmental registers
- Mendocino County's boundary and the 2,244,354 acres inside itUS Census TIGER/Line 2025
- Which of 1,086 plants clear zones 9a and a ~304-day seasonGrowable Ground crop-matching engine
- The 3 ecoregions Mendocino County spans, Klamath Mountains/California High North Coast Range the largestUS EPA Level III Ecoregions
- Open occurrence records documented in Mendocino County for a tracked speciesGBIF derived datasets (CC0 / CC BY 4.0)
- Which agricultural compounds go onto Mendocino County farmland, and roughly how muchUSGS NAWQA EPest county estimates
Inherited from a wider read
- The growing challenges every California grower plans around — written at state scale, so they stay on the state guidefrom California
What this page can’t tell you
- How the season shifts across Mendocino County — the ~304 days above is one reading at its centre; the 12 towns below each carry their owntowns in this county →
- The soil pH, drainage, sun hours, and frost pockets on any one lot among Mendocino County's 2,244,354 acreswhy one lot differs from the next →
- Which of those 787 documented sites actually reaches your soil — that needs your address, the wind, and the groundwater directionhow we read the record →
- Where cold air settles, which slopes face the sun, and which way the wind runs on your own ground — none of it survives being averaged over Mendocino Countyread your own land →