Plymouth, California, sits in USDA hardiness zone 9b — a band that supports both cool-season staples and warm-season crops chosen to fit the local frost window.
Expect tomato, artichoke, fig, and california poppy to be strong candidates here; the deciding factors on any one parcel stay local — soil, sun, and drainage.
Even in Plymouth, 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 Plymouth 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 Plymouth — soil, climate, flood, and parcel records. How we handle your address.
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Plymouth — the short answer
Plymouth, California: USDA zone 9b, about 291 days between hard freezes, across 2K acres of city.
- USDA zone
- 9b
- USDA PHZM 2023
- Last hard freeze (28°F)
- Feb 21
- Amador County normal — NOAA 1991–2020, nearest to this town
- First hard freeze (28°F)
- Dec 9
- Amador County normal — NOAA 1991–2020, nearest to this town
- Days between freezes
- ~291
- Amador County normal — NOAA 1991–2020, nearest to this town
- City area
- 2K 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 Amador County’s — the closest measured record, labelled as such rather than passed off as local.
Hardiness Zone Range
Zone 9b is Plymouth's average, not your lot's — a low corner or a tree line moves it. Against Plymouth's 291-day season, see what your own ground reads.
Soil varies lot by lot — soil types explained.
What this means for growing in Plymouth
Each reading below is measured for Plymouth itself — here is what it means for a garden here, and the move an experienced grower makes about it.
Season length
From county recordsPlymouth runs about 291 days between hard freezes (read from Amador County, the closest normal to Plymouth) — 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
MeasuredPlymouth sits in USDA hardiness zone 9b.
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 Plymouth is in
Plymouth sits in the Central California Foothills and Coastal Mountains — EPA Level III, inside the wider Mediterranean California. That is read at Plymouth's own centroid rather than borrowed from Amador County.
What Grows in Plymouth
Plants matched to Plymouth's USDA zones 9b, ordered by how much hardiness margin each has here — the ones with room to spare at both ends of this town's band lead. Each links to its full growing profile.
Is it too late to plant in Plymouth?
For most of the year, no — what changes is which crops still fit the days remaining. Cool-season crops can go in from around Jan 24; tender transplants wait until two to three weeks after the last 28°F hard freeze, which lands near Feb 21 (NOAA 1991–2020 climate normals); and from midsummer, planting counts back from the first fall freeze around Dec 9 — 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.
What's on the federal record near Plymouth
Closest first, within ~10 miles of Plymouth. Listing isn't leaking, and distance isn't exposure.
- Shenandoah StationUnderground Storage Tanks · 2100 ft
- KDR ENTERPRISES DBA SHENANDOAH STATIONBrownfields · 2100 ft
- FOOTHILL GARAGE WRECKING INCBrownfields · 0.6 mi
- PLYMOUTH USED OIL CENTERBrownfields · 0.6 mi
- PACIFIC BELLBrownfields · 0.7 mi
- Plymouth ConsolidatedMining · 0.7 mi
- Plymouth Trading PostUnderground Storage Tanks · 0.9 mi
- PioneerMining · 1.0 mi
- RORYS TOWING & REPAIR INCBrownfields · 1.1 mi
- New HopeMining · 1.2 mi
- 007N010E12M001MNitrate · 1.3 mi
- GOLDEN STATE EXPLOSIVESToxics Release Inventory · 1.4 mi
6 more sites are on the record inside the same radius. See them on the map
Measured from Plymouth'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 Plymouth.
Sources Checked
within ~10 miles of Plymouth
Severity Distribution
within ~10 miles of Plymouth
Highest-Severity Sites
A note from Gnorman
What an experienced grower watches for around here
In and around Plymouth, two things run higher than the national average within ~10 miles of Plymouth — Mining (97 sites) and Brownfields (151 sites). It's not cause for alarm — it's worth knowing, and there's a sensible way to grow around it.
Mining: Mining sites — both historic and active — can leach heavy metals (arsenic, lead, cadmium, mercury) into soil and water for centuries after operations cease.
Brownfields: Brownfield sites are former commercial or industrial properties where legacy soil contamination (heavy metals, PAHs, petroleum compounds) may persist.
Test soil for heavy metals (lead, arsenic, cadmium, mercury) — this is essential near any mining site.
Check EPA brownfield remediation status — many sites have completed cleanup with institutional controls.
Check your specific parcel in Plymouth
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 Plymouth average
Your land is one point inside Plymouth
Everything above resolves to Plymouth as a whole — one PHZM band, read across 2K acres, with hard-freeze dates borrowed from Amador 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 Plymouth Average
Plymouth Average
- ●USDA Zones 9b, averaged across Plymouth
- ●One soil character for all of Plymouth
- ●Frost dates read at Plymouth's scale: Feb 21 to Dec 9
YOUR Parcel
- ✓Your exact zone, not Plymouth's 9b
- ✓Your SSURGO soil type & pH
- ✓Your sun exposure, cast in 3D
See MY Growing Report
Read your specific parcel in Plymouth
Pull a site-specific report for your exact address in Plymouth, California — soil, sun, drainage, frost risk, and scored plant recommendations.
Three things about your lot that Plymouth averages can't show:
We read public map data around Plymouth — soil, climate, flood, and parcel records. How we handle your address.
25+ data sources read at your address, not the Plymouth average
How we know this about Plymouth
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 Amador 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 Plymouth
When does frost risk typically end in Plymouth?
The last hard freeze (28°F) in Plymouth typically lands around Feb 21, 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 14.
When is the first frost in Plymouth?
The first hard freeze (28°F) in Plymouth typically arrives around Dec 9, per NOAA 1991–2020 climate normals — the point tender summer crops finish. Lighter frosts run ahead of it, near Nov 25, so the watching starts about Nov 9 — about 291 days after the spring freeze cleared.
How long is the growing season in Plymouth?
Measured between 28°F hard freezes, Plymouth sees about 291 frost-free days — roughly Feb 21 through Dec 9, per NOAA 1991–2020 climate normals. Tender crops work a shorter one: nearer Mar 14 to Nov 25, about 256 days.
Is the soil safe to grow vegetables in Plymouth?
The federal record around Plymouth runs heavier than most — 304 documented sites, mostly Brownfields entries (151), the nearest Underground Storage Tanks record about 0.4 miles out — 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.
How do I protect my plants from frost in Plymouth?
From about Nov 9 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 Dec 9 (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 Dec 9. Hardy greens and roots shrug off light frost and sweeten after it — leave them in.
Everything above is measured at Plymouth's scale — its 9b band and its 291-day season. Your yard writes its own version of Plymouth'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 Plymouth’s own scale
4 of the readings below were taken at Plymouth's own scale — the 1,696 acres it covers and 304 documented sites around it; 6 are borrowed from a wider read, named and linked below.
Measured here
- Plymouth's own USDA hardiness band, zones 9bUSDA PHZM 2023
- 304 documented contamination sites on the federal record near Plymouth, the closest Underground Storage Tanks record about 0.4 miles out from the town centreFederal environmental registers
- Plymouth's boundary and the 1,696 acres inside itUS Census TIGER/Line 2025
- The ecoregion at Plymouth's own centroid, the Central California Foothills and Coastal MountainsUS EPA Level III Ecoregions
Inherited from a wider read
- The 28°F hard-freeze dates — Plymouth has no normal of its own, so its county's is the closest measured readfrom Amador County
- Soil character — no town-scale survey exists, so Plymouth's 1,696 acres read through its county's SSURGO summaryfrom Amador County
- The candidate plant list — California's curated set, filtered to this zone band and re-ordered by how much margin each has herefrom California
- Growing-degree days and winter chill — measured county-wide only, so the county page carries themfrom Amador County
- The growing challenges every California grower plans around — written at state scale, so they stay on the state guidefrom California
- Butterfly and beetle records, and the farmland pesticide estimate — all published county-widefrom Amador County
What this page can’t tell you
- The soil pH, drainage, sun hours, and frost pockets on any one lot among Plymouth's 1,696 acreswhy one lot differs from the next →
- Which side of Plymouth you're on — a low spot frosts first and a south wall warms early, and one normal is being asked to speak for all 1,696 acresreading your own microclimate →
- How close that record sits to YOUR lot — the closest Underground Storage Tanks record about 0.4 miles 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 Plymouth-wide figureread your own land →
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