Los Osos, California, sits in USDA hardiness zone 10a — a zone band wide enough that plant choice, not possibility, is the interesting question.
Well-matched crops include avocado, meyer lemon, tomato, and artichoke, and the gap between "grows in the area" and "grows in your yard" is closed by soil, sun, and drainage.
Even in Los Osos, 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 Los Osos 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 Los Osos — soil, climate, flood, and parcel records. How we handle your address.
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Los Osos — the short answer
Los Osos, California: USDA zone 10a, about 228 days between hard freezes, across 8K acres of town.
- USDA zone
- 10a
- USDA PHZM 2023
- Last hard freeze (28°F)
- Apr 1
- San Luis Obispo County normal — NOAA 1991–2020, nearest to this town
- First hard freeze (28°F)
- Nov 15
- San Luis Obispo County normal — NOAA 1991–2020, nearest to this town
- Days between freezes
- ~228
- San Luis Obispo County normal — NOAA 1991–2020, nearest to this town
- Town area
- 8K 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 San Luis Obispo County’s — the closest measured record, labelled as such rather than passed off as local.
Hardiness Zone Range
Zone 10a is Los Osos's average, not your lot's — a low corner or a tree line moves it. Against Los Osos's 228-day season, see what your own ground reads.
Soil varies lot by lot — soil types explained.
What this means for growing in Los Osos
Each reading below is measured for Los Osos itself — here is what it means for a garden here, and the move an experienced grower makes about it.
Season length
From county recordsLos Osos runs about 228 days between hard freezes (read from San Luis Obispo County, the closest normal to Los Osos) — a long growing season.
There is slack for succession plantings and slow-finishing crops: many vegetables can be sown twice, and the heat-lovers have time to ripen fully.
Plan a second sowing of quick crops after the first comes out, and use the fall window most gardeners let sit idle.
NOAA 1991–2020 Climate Normals
Winter hardiness
MeasuredLos Osos 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 Los Osos is in
Los Osos sits in the Central California Foothills and Coastal Mountains — EPA Level III, inside the wider Mediterranean California. That is read at Los Osos's own centroid rather than borrowed from San Luis Obispo County.
What Grows in Los Osos
Plants matched to Los Osos's USDA zones 10a, 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 Los Osos?
Usually not — gardeners here simply switch what goes in the ground as the season moves. Cool-season crops can go in from around Mar 4; tender transplants wait until two to three weeks after the last 28°F hard freeze, which lands near Apr 1 (NOAA 1991–2020 climate normals); and from midsummer, planting counts back from the first fall freeze around Nov 15 — long-season crops need about 90 days of runway, quick greens only 30. Here the season winds down slowly: late sowings, a real autumn harvest, and garlic in the ground before the first hard freeze.
What's on the federal record near Los Osos
Closest first, within ~10 miles of Los Osos. Listing isn't leaking, and distance isn't exposure.
- FRANK MERRILL BACK HOE SERVICESBrownfields · 750 ft
- RALPHS GROCERY COMPANY #271Brownfields · 1500 ft
- LOS OSOS VILLAGE SQUARE, INC.Brownfields · 1800 ft
- SMITTY'S AUTO CENTERBrownfields · 2200 ft
- BAY AUTO + TIREBrownfields · 2200 ft
- RITE AID #5821Brownfields · 2200 ft
- CENTRAL COAST AUTOHAUSBrownfields · 2300 ft
- RANTECBrownfields · 2400 ft
- PACIFIC AUTO SERVICE, INC.Brownfields · 2500 ft
- RANTEC POWER SYSTEMS INCToxics Release Inventory · 2600 ft
- DON'S AUTO REPAIRBrownfields · 0.5 mi
- ALS SEPTIC PUMPING SERVICE INCBrownfields · 0.5 mi
6 more sites are on the record inside the same radius. See them on the map
Measured from Los Osos'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 Los Osos.
Total Sites
591
within ~10 miles of Los Osos
Risk Level
Elevated
Highest-severity
1 Superfund site (none NPL-listed)
Sources Checked
within ~10 miles of Los Osos
Severity Distribution
within ~10 miles of Los Osos
Highest-Severity Sites
A note from Gnorman
What an experienced grower watches for around here
In and around Los Osos, two things run higher than the national average within ~10 miles of Los Osos — Mining (129 sites) and Brownfields (418 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 Los Osos
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 Los Osos average
Your land is one point inside Los Osos
Everything above resolves to Los Osos as a whole — one PHZM band, read across 8K acres, with hard-freeze dates borrowed from San Luis Obispo 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 Los Osos Average
Los Osos Average
- ●USDA Zones 10a, averaged across Los Osos
- ●One soil character for all of Los Osos
- ●Frost dates read at Los Osos's scale: Apr 1 to Nov 15
YOUR Parcel
- ✓Your exact zone, not Los Osos's 10a
- ✓Your SSURGO soil type & pH
- ✓Your sun exposure, cast in 3D
See MY Growing Report
Read your specific parcel in Los Osos
Pull a site-specific report for your exact address in Los Osos, California — soil, sun, drainage, frost risk, and scored plant recommendations.
Three things about your lot that Los Osos averages can't show:
We read public map data around Los Osos — soil, climate, flood, and parcel records. How we handle your address.
25+ data sources read at your address, not the Los Osos average
How we know this about Los Osos
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 San Luis Obispo 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 Los Osos
When does frost risk typically end in Los Osos?
The last hard freeze (28°F) in Los Osos typically lands around Apr 1, 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 Apr 22.
When is the first frost in Los Osos?
The first hard freeze (28°F) in Los Osos typically arrives around Nov 15, per NOAA 1991–2020 climate normals — the point tender summer crops finish. Lighter frosts run ahead of it, near Nov 1, so the watching starts about Oct 16 — about 228 days after the spring freeze cleared.
How long is the growing season in Los Osos?
Measured between 28°F hard freezes, Los Osos sees about 228 frost-free days — roughly Apr 1 through Nov 15, per NOAA 1991–2020 climate normals. Tender crops work a shorter one: nearer Apr 22 to Nov 1, about 193 days.
Is the soil safe to grow vegetables in Los Osos?
The federal record around Los Osos is a meaningful one — 591 documented sites, mostly Brownfields entries (418), the nearest Brownfields record about 0.1 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.
How do I protect my plants from frost in Los Osos?
From about Oct 16 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 15 (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 15. Hardy greens and roots shrug off light frost and sweeten after it — leave them in.
Everything above is measured at Los Osos's scale — its 10a band and its 228-day season. Your yard writes its own version of Los Osos'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 Los Osos’s own scale
4 of the readings below were taken at Los Osos's own scale — the 8,168 acres it covers and 591 documented sites around it; 6 are borrowed from a wider read, named and linked below.
Measured here
- Los Osos's own USDA hardiness band, zones 10aUSDA PHZM 2023
- 591 documented contamination sites on the federal record near Los Osos, the closest Brownfields record about 0.1 miles out from the town centreFederal environmental registers
- Los Osos's boundary and the 8,168 acres inside itUS Census TIGER/Line 2025
- The ecoregion at Los Osos'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 — Los Osos has no normal of its own, so its county's is the closest measured readfrom San Luis Obispo County
- Soil character — no town-scale survey exists, so Los Osos's 8,168 acres read through its county's SSURGO summaryfrom San Luis Obispo 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 San Luis Obispo 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 San Luis Obispo County
What this page can’t tell you
- The soil pH, drainage, sun hours, and frost pockets on any one lot among Los Osos's 8,168 acreswhy one lot differs from the next →
- Which side of Los Osos you're on — a low spot frosts first and a south wall warms early, and one normal is being asked to speak for all 8,168 acresreading your own microclimate →
- How close that record sits to YOUR lot — the closest Brownfields record about 0.1 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 Los Osos-wide figureread your own land →