Simi Valley, California, sits in USDA hardiness zone 10a — a zone band wide enough that plant choice, not possibility, is the interesting question.
Growers here do well with artichoke, meyer lemon, california poppy, and cabbage — with the usual caveat that any single yard's soil, sun, and drainage cast the deciding vote.
Even in Simi Valley, 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 Simi Valley 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 Simi Valley — soil, climate, flood, and parcel records. How we handle your address.
No card required · your full report in seconds
Simi Valley — the short answer
Simi Valley, California: USDA zone 10a, no 28°F killing freeze on record — the season is year-round, across 27K acres of city.
- USDA zone
- 10a
- USDA PHZM 2023
- Killing freeze
- None on record
- NOAA RCC ACIS 1991–2020, this town’s own record
- City area
- 27K acres
- US Census TIGER/Line 2025
Every figure names the dataset it came from. The year-round finding is measured — a 30-year record with no 28°F killing freeze in it — never inferred from missing dates.
Hardiness Zone Range
Zone 10a is Simi Valley's average, not your lot's — a low corner or a tree line moves it. Against Simi Valley's no killing freeze on record, see what your own ground reads.
Soil varies lot by lot — soil types explained.
What this means for growing in Simi Valley
Each reading below is measured for Simi Valley itself — here is what it means for a garden here, and the move an experienced grower makes about it.
Winter hardiness
MeasuredSimi Valley sits in USDA hardiness zone 10a.
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 Simi Valley is in
Simi Valley sits in the Southern California/Northern Baja Coast — EPA Level III, inside the wider Mediterranean California. That is read at Simi Valley's own centroid, and it is not what its county reads: Ventura County is mostly Southern California Mountains. The wider page above you is answering a different question about different ground.
What Grows in Simi Valley
Every plant below cleared Simi Valley's own zone 10a. Each card opens that plant's California profile. How we score.
What's on the federal record near Simi Valley
Closest first, within ~10 miles of Simi Valley. Listing isn't leaking, and distance isn't exposure.
- CHRIS HUGHESBrownfields · 1100 ft
- BERNAL, ALEXBrownfields · 1400 ft
- GRACE BRETHREN SCHOOLSBrownfields · 1500 ft
- GUY SELLARSBrownfields · 1600 ft
- SAM HAREBrownfields · 1600 ft
- SHERYL ORNELASBrownfields · 1600 ft
- VY KINGBrownfields · 1700 ft
- RICK GODINBrownfields · 1900 ft
- AT&TBrownfields · 1900 ft
- JASON JUNEBrownfields · 1900 ft
- AT&T California - KD138Underground Storage Tanks · 2100 ft
- Royal Shell Gas, Inc.Underground Storage Tanks · 2100 ft
6 more sites are on the record inside the same radius. See them on the map
Measured from Simi Valley'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 Simi Valley.
Total Sites
2,989
within ~10 miles of Simi Valley
Risk Level
Elevated
Highest-severity
5 Superfund sites (none NPL-listed)
Sources Checked
within ~10 miles of Simi Valley
Severity Distribution
within ~10 miles of Simi Valley
Highest-Severity Sites
A note from Gnorman
What an experienced grower watches for around here
In and around Simi Valley, Brownfields runs higher than the national average — 2,715 sites within ~10 miles of Simi Valley. That's not a problem with your land — it's information about it.
Brownfields: Brownfield sites are former commercial or industrial properties where legacy soil contamination (heavy metals, PAHs, petroleum compounds) may persist.
Check EPA brownfield remediation status — many sites have completed cleanup with institutional controls.
Check your specific parcel in Simi Valley
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 Simi Valley average
Your land is one point inside Simi Valley
Everything above resolves to Simi Valley as a whole — one PHZM band and one 28°F frost record, read across 27K 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 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 Simi Valley Average
Simi Valley Average
- ●USDA Zones 10a, averaged across Simi Valley
- ●One soil character for all of Simi Valley
- ●State-average frost dates
YOUR Parcel
- ✓Your exact zone, not Simi Valley's 10a
- ✓Your SSURGO soil type & pH
- ✓Your sun exposure, cast in 3D
See MY Growing Report
Read your specific parcel in Simi Valley
Pull a site-specific report for your exact address in Simi Valley, California — soil, sun, drainage, frost risk, and scored plant recommendations.
Three things about your lot that Simi Valley averages can't show:
We read public map data around Simi Valley — soil, climate, flood, and parcel records. How we handle your address.
25+ data sources read at your address, not the Simi Valley average
How we know this about Simi Valley
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, with the labelled statewide window where none resolves; 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 Simi Valley
Is it too late to plant in Simi Valley?
No — Simi Valley has no 28°F killing freeze in the 30-year station record, so the growing season is year-round and there is no last-frost date to wait for. Planting is paced by rainfall, heat and daylength instead of by frost: start heat-lovers any month, and time cool-season crops (lettuce, brassicas, peas) for the cooler, wetter half of the year or for higher ground. Succession sowing every few weeks works all year, so the limit is what you can keep watered and harvested, not the calendar.
When does frost risk typically end in Simi Valley?
It doesn't — Simi Valley records no 28°F killing freeze at all across the 1991–2020 station record, so there is no spring frost date to plant after. Cold still matters with elevation: the higher you garden, the cooler the nights, and a few tropical crops sulk below about 60°F even where they never freeze.
How long is the growing season in Simi Valley?
Year-round — the 1991–2020 station record for Simi Valley contains no 28°F killing freeze, so there is no season to measure between freezes. What paces planting instead is heat, rainfall and daylength: the hottest, wettest stretch is the hard part for cool-season crops, not winter. Elevation is the one real exception — the higher you garden, the colder the nights get.
Is the soil safe to grow vegetables in Simi Valley?
The federal record around Simi Valley is a meaningful one — 2,989 documented sites, mostly Brownfields entries (2,715), the nearest Brownfields record about 0.2 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 Simi Valley's scale — its 10a band and its no killing freeze on record. Your yard writes its own version of Simi Valley'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 Simi Valley’s own scale
6 of the readings below were taken at Simi Valley's own scale — the 26,589 acres it covers and 2,989 documented sites around it; 4 are borrowed from a wider read, named and linked below.
Measured here
- Simi Valley's own USDA hardiness band, zones 10aUSDA PHZM 2023
- No 28°F killing freeze in the 30-year station record covering Simi Valley — a year-round growing seasonNOAA Regional Climate Centers ACIS, 1991-2020
- 2,989 documented contamination sites on the federal record near Simi Valley, the closest Brownfields record about 0.2 miles out from the town centreFederal environmental registers
- Simi Valley's boundary and the 26,589 acres inside itUS Census TIGER/Line 2025
- Which of 1,086 plants clear Simi Valley's hardiness zoneGrowable Ground crop-matching engine
- Simi Valley sits in the Southern California/Northern Baja Coast — not the ecoregion its county mostly readsUS EPA Level III Ecoregions
Inherited from a wider read
- Soil character — no town-scale survey exists, so Simi Valley's 26,589 acres read through its county's SSURGO summaryfrom Ventura County
- Growing-degree days and winter chill — measured county-wide only, so the county page carries themfrom Ventura 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 Ventura County
What this page can’t tell you
- The soil pH, drainage, sun hours, and frost pockets on any one lot among Simi Valley's 26,589 acreswhy one lot differs from the next →
- Which side of Simi Valley you're on — a low spot frosts first and a south wall warms early, and one normal is being asked to speak for all 26,589 acresreading your own microclimate →
- How close that record sits to YOUR lot — the closest Brownfields record about 0.2 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 Simi Valley-wide figureread your own land →