Maxwell, California, sits in USDA hardiness zone 9b — a zone band wide enough that plant choice, not possibility, is the interesting question.
Reliable performers under these conditions include okra, meyer lemon, california poppy, and artichoke; what your own ground favors still comes down to its soil, sun, and drainage.
Even in Maxwell, 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 Maxwell 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 Maxwell — soil, climate, flood, and parcel records. How we handle your address.
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Maxwell — the short answer
Maxwell, California: USDA zone 9b, about 329 days between hard freezes, across 1K acres of town.
- USDA zone
- 9b
- USDA PHZM 2023
- Last hard freeze (28°F)
- Jan 19
- Colusa County normal — NOAA 1991–2020, nearest to this town
- First hard freeze (28°F)
- Dec 14
- Colusa County normal — NOAA 1991–2020, nearest to this town
- Days between freezes
- ~329
- Colusa County normal — NOAA 1991–2020, nearest to this town
- Town 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 Colusa County’s — the closest measured record, labelled as such rather than passed off as local.
Hardiness Zone Range
Zone 9b is Maxwell's average, not your lot's — a low corner or a tree line moves it. Against Maxwell's 329-day season, see what your own ground reads.
Soil varies lot by lot — soil types explained.
What this means for growing in Maxwell
Each reading below is measured for Maxwell itself — here is what it means for a garden here, and the move an experienced grower makes about it.
Season length
From county recordsMaxwell runs about 329 days between hard freezes (read from Colusa County, the closest normal to Maxwell) — 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
MeasuredMaxwell 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 Maxwell is in
Maxwell sits in the Central California Valley — EPA Level III, inside the wider Mediterranean California. That is read at Maxwell's own centroid rather than borrowed from Colusa County.
What Grows in Maxwell
Every plant below cleared Maxwell's own zone 9b and its 329-day season. Each card opens that plant's California profile. How we score.
Is it too late to plant in Maxwell?
Rarely: the season closes in stages, not all at once, and each stage has its crops. Cool-season crops can go in from around Jan 1; tender transplants wait until two to three weeks after the last 28°F hard freeze, which lands near Jan 19 (NOAA 1991–2020 climate normals); and from midsummer, planting counts back from the first fall freeze around Dec 14 — long-season crops need about 90 days of runway, quick greens only 30. In a climate this gentle, “too late” hardly applies — the question becomes which crops prefer the cooler months ahead.
What's on the federal record near Maxwell
Closest first, within ~10 miles of Maxwell. Listing isn't leaking, and distance isn't exposure.
- MAXWELL CHEVRONUnderground Storage Tanks · 300 ft
- CALDWELLS MINI MARTUnderground Storage Tanks · 300 ft
- 017N003W33R001MNitrate · 550 ft
- BARBER CASHEW LEASE PROPERTYBrownfields · 850 ft
- CALDWELL'S MINI MARTBrownfields · 900 ft
- MAXWELL SUBSTATIONBrownfields · 1100 ft
- MAXWELL USDBrownfields · 1200 ft
- CONNER RANCH A PARTNERSHIPBrownfields · 1300 ft
- 017N003W33R002MNitrate · 1900 ft
- CALTRANS D-03/ 03-3F7804Brownfields · 2400 ft
- H & A ANDREOTTI FARMSBrownfields · 2500 ft
- RICHTER AVIATION INCBrownfields · 2500 ft
6 more sites are on the record inside the same radius. See them on the map
Measured from Maxwell'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 Maxwell.
Total Sites
166
within ~10 miles of Maxwell
Risk Level
Moderate
Highest-severity
1 Toxics Release Inventory facility
Sources Checked
within ~10 miles of Maxwell
Severity Distribution
within ~10 miles of Maxwell
Highest-Severity Sites
A note from Gnorman
What an experienced grower watches for around here
In and around Maxwell, Nitrate runs higher than the national average — 74 sites within ~10 miles of Maxwell. That's not a problem with your land — it's information about it.
Nitrate: Nitrate contamination primarily comes from agricultural fertilizer runoff and failing septic systems.
Test well water for nitrate if you rely on a private well for irrigation (EPA standard: 10 mg/L).
Check your specific parcel in Maxwell
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 Maxwell average
Your land is one point inside Maxwell
Everything above resolves to Maxwell as a whole — one PHZM band, read across 1K acres, with hard-freeze dates borrowed from Colusa County’s record because no 30-year normal resolves at this town’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 town 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 Maxwell Average
Maxwell Average
- ●USDA Zones 9b, averaged across Maxwell
- ●One soil character for all of Maxwell
- ●Frost dates read at Maxwell's scale: Jan 19 to Dec 14
YOUR Parcel
- ✓Your exact zone, not Maxwell's 9b
- ✓Your SSURGO soil type & pH
- ✓Your sun exposure, cast in 3D
See MY Growing Report
Read your specific parcel in Maxwell
Pull a site-specific report for your exact address in Maxwell, California — soil, sun, drainage, frost risk, and scored plant recommendations.
Three things about your lot that Maxwell averages can't show:
We read public map data around Maxwell — soil, climate, flood, and parcel records. How we handle your address.
25+ data sources read at your address, not the Maxwell average
How we know this about Maxwell
The datasets: hardiness from the USDA ARS Plant Hardiness Zone Map 2023, read at this town’s own centroid; hard-freeze dates from NOAA 1991–2020 28°F normals at Colusa 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 town grain anywhere on this page — there is no town-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 Maxwell
When does frost risk typically end in Maxwell?
The last hard freeze (28°F) in Maxwell typically lands around Jan 19, 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 9.
When is the first frost in Maxwell?
The first hard freeze (28°F) in Maxwell typically arrives around Dec 14, per NOAA 1991–2020 climate normals — the point tender summer crops finish. Lighter frosts run ahead of it, near Nov 30, so the watching starts about Nov 14 — about 329 days after the spring freeze cleared.
How long is the growing season in Maxwell?
Measured between 28°F hard freezes, Maxwell sees about 329 frost-free days — roughly Jan 19 through Dec 14, per NOAA 1991–2020 climate normals. Tender crops work a shorter one: nearer Feb 9 to Nov 30, about 294 days.
Is the soil safe to grow vegetables in Maxwell?
The federal record around Maxwell shows 166 documented sites, mostly Brownfields entries (79), the nearest Underground Storage Tanks record under a tenth of a mile out — a typical footprint for a growing area, and proximity to a documented site is information, not a diagnosis of any one yard. It's worth seeing which recorded sites sit closest to where you grow, and testing the soil before new food beds near any of them.
How do I protect my plants from frost in Maxwell?
From about Nov 14 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 14 (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 14. Hardy greens and roots shrug off light frost and sweeten after it — leave them in.
Everything above is measured at Maxwell's scale — its 9b band and its 329-day season. Your yard writes its own version of Maxwell'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 Maxwell’s own scale
5 of the readings below were taken at Maxwell's own scale — the 1,376 acres it covers and 166 documented sites around it; 5 are borrowed from a wider read, named and linked below.
Measured here
- Maxwell's own USDA hardiness band, zones 9bUSDA PHZM 2023
- 166 documented contamination sites on the federal record near Maxwell, the closest Underground Storage Tanks record under a tenth of a mile out from the town centreFederal environmental registers
- Maxwell's boundary and the 1,376 acres inside itUS Census TIGER/Line 2025
- Which of 1,086 plants clear zones 9b and a ~329-day seasonGrowable Ground crop-matching engine
- The ecoregion at Maxwell's own centroid, the Central California ValleyUS EPA Level III Ecoregions
Inherited from a wider read
- The 28°F hard-freeze dates — Maxwell has no normal of its own, so its county's is the closest measured readfrom Colusa County
- Soil character — no town-scale survey exists, so Maxwell's 1,376 acres read through its county's SSURGO summaryfrom Colusa County
- Growing-degree days and winter chill — measured county-wide only, so the county page carries themfrom Colusa 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 Colusa County
What this page can’t tell you
- The soil pH, drainage, sun hours, and frost pockets on any one lot among Maxwell's 1,376 acreswhy one lot differs from the next →
- Which side of Maxwell you're on — a low spot frosts first and a south wall warms early, and one normal is being asked to speak for all 1,376 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 Maxwell-wide figureread your own land →