Onyx, California, sits in USDA hardiness zone 9a — enough range to grow cool-season vegetables, hardy fruit, and warm-season crops that mature before the first hard frost.
Expect artichoke, fig, california poppy, and cabbage to be strong candidates here; the deciding factors on any one parcel stay local — soil, sun, and drainage.
Even in Onyx, 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 Onyx 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 Onyx — soil, climate, flood, and parcel records. How we handle your address.
No card required · your full report in seconds
Onyx — the short answer
Onyx, California: USDA zone 9a, about 276 days between hard freezes, across 7K acres of town.
- USDA zone
- 9a
- USDA PHZM 2023
- Last hard freeze (28°F)
- Feb 28
- NOAA 1991–2020 Climate Normals, 28°F — this town
- First hard freeze (28°F)
- Dec 1
- NOAA 1991–2020 Climate Normals, 28°F — this town
- Days between freezes
- ~276
- NOAA 1991–2020 Climate Normals, 28°F — this town
- Town area
- 7K acres
- US Census TIGER/Line 2025
Every figure names the dataset it came from. Hard-freeze dates are this town’s own 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 Onyx's average, not your lot's — a low corner or a tree line moves it. Against Onyx's 276-day season, see what your own ground reads.
Soil varies lot by lot — soil types explained.
What this means for growing in Onyx
Each reading below is measured for Onyx itself — here is what it means for a garden here, and the move an experienced grower makes about it.
Season length
MeasuredOnyx runs about 276 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
MeasuredOnyx 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 Onyx is in
Onyx sits in the Sierra Nevada — EPA Level III, inside the wider Northwestern Forested Mountains. That is read at Onyx's own centroid, and it is not what its county reads: Kern County is mostly Central California Valley. The wider page above you is answering a different question about different ground.
What Grows in Onyx
Every plant below cleared Onyx's own zone 9a and its 276-day season. Each card opens that plant's California profile. How we score.
Is it too late to plant in Onyx?
Almost never — the real question is what to plant next. Cool-season crops can go in from around Jan 31; tender transplants wait until two to three weeks after the last 28°F hard freeze, which lands near Feb 28 (NOAA 1991–2020 climate normals); and from midsummer, planting counts back from the first fall freeze around Dec 1 — 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 Onyx
Closest first, within ~10 miles of Onyx. Listing isn't leaking, and distance isn't exposure.
- ROPER RECYCLINGUnderground Storage Tanks · 1.6 mi
- ROSEDALE-RIO BRAVO WATER STORAGE DISTRICTBrownfields · 1.9 mi
- 026S035E03E001MNitrate · 2.0 mi
- WILLIAM D CREIGHTONBrownfields · 2.2 mi
- MORELAND IND EVENING STAR MILLBrownfields · 2.3 mi
- WITTEN LOGGING COBrownfields · 2.3 mi
- SOUTH FORK UNION SDBrownfields · 3.5 mi
- 026S034E14J001MNitrate · 3.7 mi
- CALPORTLAND NORTH SKY READY MIX PLANTToxics Release Inventory · 4.2 mi
- RICHARD'S MOBILE TRUCK & AUTO REPAIR SERVICEBrownfields · 4.5 mi
- HAFENFELD RANCHBrownfields · 5.4 mi
- Last Chance MineMining · 5.5 mi
6 more sites are on the record inside the same radius. See them on the map
Measured from Onyx'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 Onyx.
Total Sites
36
within ~10 miles of Onyx
Risk Level
Moderate
Highest-severity
1 Toxics Release Inventory facility
Sources Checked
within ~10 miles of Onyx
Severity Distribution
within ~10 miles of Onyx
Highest-Severity Sites
A note from Gnorman
What an experienced grower watches for around here
In and around Onyx, two things run higher than the national average within ~10 miles of Onyx — Mining (7 sites) and Brownfields (19 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 Onyx
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 Onyx average
Your land is one point inside Onyx
Everything above resolves to Onyx as a whole — one PHZM band and one 28°F frost record, read across 7K 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 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 Onyx Average
Onyx Average
- ●USDA Zones 9a, averaged across Onyx
- ●One soil character for all of Onyx
- ●Frost dates read at Onyx's scale: Feb 28 to Dec 1
YOUR Parcel
- ✓Your exact zone, not Onyx's 9a
- ✓Your SSURGO soil type & pH
- ✓Your sun exposure, cast in 3D
See MY Growing Report
Read your specific parcel in Onyx
Pull a site-specific report for your exact address in Onyx, California — soil, sun, drainage, frost risk, and scored plant recommendations.
Three things about your lot that Onyx averages can't show:
We read public map data around Onyx — soil, climate, flood, and parcel records. How we handle your address.
25+ data sources read at your address, not the Onyx average
How we know this about Onyx
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 Onyx’s own record; 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 Onyx
When does frost risk typically end in Onyx?
The last hard freeze (28°F) in Onyx typically lands around Feb 28, 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 21.
When is the first frost in Onyx?
The first hard freeze (28°F) in Onyx typically arrives around Dec 1, per NOAA 1991–2020 climate normals — the point tender summer crops finish. Lighter frosts run ahead of it, near Nov 17, so the watching starts about Nov 1 — about 276 days after the spring freeze cleared.
How long is the growing season in Onyx?
Measured between 28°F hard freezes, Onyx sees about 276 frost-free days — roughly Feb 28 through Dec 1, per NOAA 1991–2020 climate normals. Tender crops work a shorter one: nearer Mar 21 to Nov 17, about 241 days.
Is the soil safe to grow vegetables in Onyx?
The federal record around Onyx shows 36 documented sites, mostly Brownfields entries (19), the nearest Underground Storage Tanks record about 1.6 miles 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 Onyx?
From about Nov 1 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 1 (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 1. Hardy greens and roots shrug off light frost and sweeten after it — leave them in.
Everything above is measured at Onyx's scale — its 9a band and its 276-day season. Your yard writes its own version of Onyx'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 Onyx’s own scale
6 of the readings below were taken at Onyx's own scale — its own ~276-day season between 28°F freezes, the 7,329 acres it covers and 36 documented sites around it; 4 are borrowed from a wider read, named and linked below.
Measured here
- Onyx's own USDA hardiness band, zones 9aUSDA PHZM 2023
- Onyx's own 28°F hard-freeze dates, about Feb 28 and Dec 1 and the ~276-day span between themNOAA 1991–2020 Climate Normals
- 36 documented contamination sites on the federal record near Onyx, the closest Underground Storage Tanks record about 1.6 miles out from the town centreFederal environmental registers
- Onyx's boundary and the 7,329 acres inside itUS Census TIGER/Line 2025
- Which of 1,086 plants clear zones 9a and a ~276-day seasonGrowable Ground crop-matching engine
- Onyx sits in the Sierra Nevada — not the ecoregion its county mostly readsUS EPA Level III Ecoregions
Inherited from a wider read
- Soil character — no town-scale survey exists, so Onyx's 7,329 acres read through its county's SSURGO summaryfrom Kern County
- Growing-degree days and winter chill — measured county-wide only, so the county page carries themfrom Kern 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 Kern County
What this page can’t tell you
- The soil pH, drainage, sun hours, and frost pockets on any one lot among Onyx's 7,329 acreswhy one lot differs from the next →
- Which side of Onyx you're on — a low spot frosts first and a south wall warms early, and one normal is being asked to speak for all 7,329 acresreading your own microclimate →
- How close that record sits to YOUR lot — the closest Underground Storage Tanks record about 1.6 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 Onyx-wide figureread your own land →