Walnut Creek, California, sits in USDA hardiness zone 9b — a zone band wide enough that plant choice, not possibility, is the interesting question.
On paper, okra, meyer lemon, california poppy, and artichoke all suit these conditions — on the ground, soil, sun, and drainage make the final call.
Even in Walnut Creek, 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 Walnut Creek 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 Walnut Creek — soil, climate, flood, and parcel records. How we handle your address.
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Walnut Creek — the short answer
Walnut Creek, California: USDA zone 9b, about 332 days between hard freezes, across 13K acres of city.
- USDA zone
- 9b
- USDA PHZM 2023
- Last hard freeze (28°F)
- Jan 16
- Contra Costa County normal — NOAA 1991–2020, nearest to this town
- First hard freeze (28°F)
- Dec 14
- Contra Costa County normal — NOAA 1991–2020, nearest to this town
- Days between freezes
- ~332
- Contra Costa County normal — NOAA 1991–2020, nearest to this town
- City area
- 13K 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 Contra Costa County’s — the closest measured record, labelled as such rather than passed off as local.
Hardiness Zone Range
Zone 9b is Walnut Creek's average, not your lot's — a low corner or a tree line moves it. Against Walnut Creek's 332-day season, see what your own ground reads.
Soil varies lot by lot — soil types explained.
What this means for growing in Walnut Creek
Each reading below is measured for Walnut Creek itself — here is what it means for a garden here, and the move an experienced grower makes about it.
Season length
From county recordsWalnut Creek runs about 332 days between hard freezes (read from Contra Costa County, the closest normal to Walnut Creek) — 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
MeasuredWalnut Creek 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 Walnut Creek is in
Walnut Creek sits in the Central California Foothills and Coastal Mountains — EPA Level III, inside the wider Mediterranean California. That is read at Walnut Creek's own centroid rather than borrowed from Contra Costa County.
What Grows in Walnut Creek
Every plant below cleared Walnut Creek's own zone 9b and its 332-day season. Each card opens that plant's California profile. How we score.
Is it too late to plant in Walnut Creek?
Usually not — gardeners here simply switch what goes in the ground as the season moves. 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 16 (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. Here the calendar nearly circles: cool-season crops take the winter shift, and the next window is always close.
Documented around Walnut Creek
Spotted lanternfly documented 15 miles from Walnut Creek, first recorded 2023. What to watch for.
What's on the federal record near Walnut Creek
Closest first, within ~10 miles of Walnut Creek. Listing isn't leaking, and distance isn't exposure.
- KELSEY GRAYBrownfields · 1300 ft
- DAN DRUMMONDBrownfields · 1500 ft
- ROB & LISA MICHELANGELIBrownfields · 1600 ft
- KEN SIMASBrownfields · 1800 ft
- STEVE IVERSONBrownfields · 1800 ft
- 1429 VIA LOMABrownfields · 2600 ft
- JOHN MUIR HEALTH WOUND CARE CLINICBrownfields · 0.5 mi
- LESLIE WILSONBrownfields · 0.5 mi
- DR SCOTT & DR MATTINGLEY DDSBrownfields · 0.6 mi
- HENRY SICABAIGBrownfields · 0.6 mi
- AL BASCOUBrownfields · 0.6 mi
- 19 SUTTER'S MILLBrownfields · 0.6 mi
6 more sites are on the record inside the same radius. See them on the map
Measured from Walnut Creek'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 Walnut Creek.
Total Sites
3,038
within ~10 miles of Walnut Creek
Risk Level
Elevated
Highest-severity
5 Superfund sites (none NPL-listed)
Sources Checked
within ~10 miles of Walnut Creek
Severity Distribution
within ~10 miles of Walnut Creek
Highest-Severity Sites
A note from Gnorman
What an experienced grower watches for around here
In and around Walnut Creek, Brownfields runs higher than the national average — 2,783 sites within ~10 miles of Walnut Creek. It's not cause for alarm — it's worth knowing, and there's a sensible way to grow around 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 Walnut Creek
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 Walnut Creek average
Your land is one point inside Walnut Creek
Everything above resolves to Walnut Creek as a whole — one PHZM band, read across 13K acres, with hard-freeze dates borrowed from Contra Costa 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 Walnut Creek Average
Walnut Creek Average
- ●USDA Zones 9b, averaged across Walnut Creek
- ●One soil character for all of Walnut Creek
- ●Frost dates read at Walnut Creek's scale: Jan 16 to Dec 14
YOUR Parcel
- ✓Your exact zone, not Walnut Creek's 9b
- ✓Your SSURGO soil type & pH
- ✓Your sun exposure, cast in 3D
See MY Growing Report
Read your specific parcel in Walnut Creek
Pull a site-specific report for your exact address in Walnut Creek, California — soil, sun, drainage, frost risk, and scored plant recommendations.
Three things about your lot that Walnut Creek averages can't show:
We read public map data around Walnut Creek — soil, climate, flood, and parcel records. How we handle your address.
25+ data sources read at your address, not the Walnut Creek average
How we know this about Walnut Creek
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 Contra Costa 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 Walnut Creek
When does frost risk typically end in Walnut Creek?
The last hard freeze (28°F) in Walnut Creek typically lands around Jan 16, 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 6.
When is the first frost in Walnut Creek?
The first hard freeze (28°F) in Walnut Creek 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 332 days after the spring freeze cleared.
How long is the growing season in Walnut Creek?
Measured between 28°F hard freezes, Walnut Creek sees about 332 frost-free days — roughly Jan 16 through Dec 14, per NOAA 1991–2020 climate normals. Tender crops work a shorter one: nearer Feb 6 to Nov 30, about 297 days.
Is the soil safe to grow vegetables in Walnut Creek?
The federal record around Walnut Creek is a meaningful one — 3,038 documented sites, mostly Brownfields entries (2,783), 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.
How do I protect my plants from frost in Walnut Creek?
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 Walnut Creek's scale — its 9b band and its 332-day season. Your yard writes its own version of Walnut Creek'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 Walnut Creek’s own scale
6 of the readings below were taken at Walnut Creek's own scale — the 12,646 acres it covers and 3,038 documented sites around it; 5 are borrowed from a wider read, named and linked below.
Measured here
- Walnut Creek's own USDA hardiness band, zones 9bUSDA PHZM 2023
- 3,038 documented contamination sites on the federal record near Walnut Creek, the closest Brownfields record about 0.2 miles out from the town centreFederal environmental registers
- Walnut Creek's boundary and the 12,646 acres inside itUS Census TIGER/Line 2025
- Which of 1,086 plants clear zones 9b and a ~332-day seasonGrowable Ground crop-matching engine
- The ecoregion at Walnut Creek's own centroid, the Central California Foothills and Coastal MountainsUS EPA Level III Ecoregions
- A documented spotted-lanternfly record within reach of Walnut Creeklydemapr (De Bona & Helmus), 10 km survey lattice
Inherited from a wider read
- The 28°F hard-freeze dates — Walnut Creek has no normal of its own, so its county's is the closest measured readfrom Contra Costa County
- Soil character — no town-scale survey exists, so Walnut Creek's 12,646 acres read through its county's SSURGO summaryfrom Contra Costa County
- Growing-degree days and winter chill — measured county-wide only, so the county page carries themfrom Contra Costa 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 Contra Costa County
What this page can’t tell you
- The soil pH, drainage, sun hours, and frost pockets on any one lot among Walnut Creek's 12,646 acreswhy one lot differs from the next →
- Which side of Walnut Creek you're on — a low spot frosts first and a south wall warms early, and one normal is being asked to speak for all 12,646 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 Walnut Creek-wide figureread your own land →