Alameda County, in California, sits in USDA hardiness zone 9b — enough range to grow cool-season vegetables, hardy fruit, and warm-season crops that mature before the first hard frost.
Growers here do well with okra, meyer lemon, california poppy, and artichoke — with the usual caveat that any single yard's soil, sun, and drainage cast the deciding vote.
Alameda County lies within the Livermore Valley and the San Francisco Bay Area — a regional growing area with its own character.
Grounded in USDA PHZM 2023 · Growable Ground suitability scoring · NOAA 1991–2020 Climate Normals
Alameda County holds more than one microclimate.
Soils and elevations shift across Alameda County, so your frost dates and drainage aren't the county average. 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 Alameda County — soil, climate, flood, and parcel records. How we handle your address.
No card required · your full report in seconds
Alameda County — the short answer
Alameda County, California: USDA zone 9b, about 334 days between hard freezes, across 472K acres.
- USDA zone
- 9b
- USDA PHZM 2023
- Last hard freeze (28°F)
- Jan 12
- NOAA 1991–2020 Climate Normals, 28°F
- First hard freeze (28°F)
- Dec 12
- NOAA 1991–2020 Climate Normals, 28°F
- Days between freezes
- ~334
- NOAA 1991–2020 Climate Normals, 28°F
- County area
- 472K acres
- US Census TIGER/Line 2025
Every figure names the dataset it came from. Hard-freeze dates are county 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 9b is Alameda County's average, not your lot's — a low corner or a tree line moves it. Against Alameda County's 334-day season, see what your own ground reads.
Heat and winter chill in Alameda County
Across a year, Alameda County accumulates about 3,757 growing degree days above 50°F, right at the California middle — ahead of 28 of California’s 57 counties. Degree days are the heat a crop actually gets to work with — more of them is more room to ripen a long-season crop before the freeze closes the window.
Winter banks about 806 hours below 45°F, 381 fewer than the California middle of 1,187. Chill is what tells a fruit tree its dormancy is over, and it is set by climate rather than by anything you can build.
Grounded in PRISM Climate Group, Oregon State University — 1991–2020 monthly normals
Soil in Alameda County
Across Alameda County, the ground is predominantly Alfisols, where Vallecitos, Los Osos, and Millsholm are the most extensive named soil series. The soil is generally well drained with a clay surface. Topsoil pH runs about 6.1–7.3, neutral. Rainfall drains through hydrologic group D soils.
Soil order
Alfisols
Drainage
Well drained
Hydric soils
14%
Soil still varies lot by lot — soil types explained.
How the ground varies across Alameda County
The USDA soil survey maps 55% of Alameda County as well drained — but another 25% drains differently: 8% somewhat excessively drained, 7% poorly drained.
Vallecitos is the most extensive named soil at 12% of mapped acres, then Los Osos (9%) and Millsholm (8%).
Which of them your own lot sits on is a parcel question, not a county one. Check your address for the survey at your boundary.
What this means for growing in Alameda County
Each reading below is measured for Alameda County itself — here is what it means for a garden here, and the move an experienced grower makes about it.
Drainage
MeasuredThe dominant soils across Alameda County are well drained, in hydrologic group D — ground that drains quickly.
The upside is soil you can work early in spring and roots that never drown; the cost is that fast-draining ground dries out fast and leaches nutrients away before plants can use them.
Work in compost and mulch to hold moisture and feed, and water more often in short doses than deep and rarely.
USDA NRCS SSURGO
Surface pH
MeasuredTopsoil across Alameda County runs about pH 6.1–7.3, close to neutral.
This is the range most vegetables prefer — one correction you probably do not have to make, which is genuinely good news for a new bed.
Keep it there with compost rather than lime or sulfur, and only amend if your own soil test says otherwise.
USDA NRCS SSURGO
Season length
MeasuredAlameda County runs about 334 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
MeasuredAlameda County 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 Alameda County is in
Alameda County sits in the Central California Foothills and Coastal Mountains — EPA Level III, inside the wider Mediterranean California. One consistent ecological setting across the whole county.
What Grows in Alameda County
We scored all 1,086 plants against Alameda County's own USDA zone 9b and its own 334-day season between hard freezes, using the same matching engine that runs a full parcel report. These cleared both. Sun, soil pH and drainage vary lot by lot — those are the parcel questions below. Each card opens that plant's California profile.
Is it too late to plant in Alameda County?
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 12 (NOAA 1991–2020 climate normals); and from midsummer, planting counts back from the first fall freeze around Dec 12 — 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 Alameda County
Spotted lanternfly documented 19 miles from Alameda County, first recorded 2023. What to watch for.
- monarch butterfly492 documented records
Sighting records, so they follow observers as much as insects.
What gets applied to farmland in Alameda County
USGS estimates 6,561 lb of Glyphosate on Alameda County farmland in 2019, its largest by weight, ahead of Cyprodinil (638 lb) and Imidacloprid (509 lb).
Farmland across the whole county, not any one lot. Check your address for the site-by-site record.
Safe to Grow Here?
What the federal record shows across Alameda County — and how to grow with it.
We checked the federal record across Alameda County — 11,350 documented sites across 7 of the 9 source types we track.
The most significant on record: 48 Superfund sites. Sites tracked in EPA's Superfund program — from assessment-stage CERCLIS entries to confirmed National Priorities List cleanup sites.
Alameda County carries one of the heavier federal records we track — and that's not a verdict on your yard. Proximity to a documented site is information, not a diagnosis: nothing here says any particular parcel is affected. It does earn one concrete step — before food beds go in the ground, a professional soil test tells you exactly what you're working with, and raised beds with clean imported soil grow well almost anywhere in the meantime.
Sources: EPA, USGS — 1.8M documented sites tracked nationwide across 9 federal source types.
What's on the federal record near Alameda County
Closest first, across Alameda County. Listing isn't leaking, and distance isn't exposure.
- 003S001E30G003MNitrate · 0.7 mi
- 003S001E30A009MNitrate · 0.8 mi
- 003S001E19K001MNitrate · 0.8 mi
- AT&T MOBILITYBrownfields · 0.8 mi
- 003S001E30A008MNitrate · 0.8 mi
- 003S001E30A011MNitrate · 0.8 mi
- 003S001E29M004MNitrate · 0.9 mi
- Safeway Fuel Center #2856Underground Storage Tanks · 1.0 mi
- PLEASANTON GOLF CENTERBrownfields · 1.0 mi
- SAFEWAY 2856Brownfields · 1.0 mi
- UNCHAINED LABSBrownfields · 1.0 mi
- SAFEWAY STORE #2856Brownfields · 1.0 mi
6 more sites are on the record inside the same radius. See them on the map
Measured from Alameda County'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 Alameda County.
Sources Checked
across Alameda County
Severity Distribution
across Alameda County
Highest-Severity Sites
A note from Gnorman
What an experienced grower watches for around here
In and around Alameda County, Brownfields runs higher than the national average — 9,842 sites across Alameda County. 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 Alameda County
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 Alameda County average
Your land is one point inside Alameda County
Everything above resolves to Alameda County as a whole — one PHZM band and one county frost record, read across 472K 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 county 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 county average.
Your Lot vs the Alameda County Average
Alameda County Average
- ●USDA Zones 9b, averaged across Alameda County
- ●One soil character for all of Alameda County
- ●Frost dates read at Alameda County's scale: Jan 12 to Dec 12
YOUR Parcel
- ✓Your exact zone, not Alameda County's 9b
- ✓Your SSURGO soil type & pH
- ✓Your sun exposure, cast in 3D
See MY Growing Report
Read your parcel in Alameda County
Pull a site-specific report for your exact address in Alameda County, California — soil, sun, drainage, frost risk, and scored plant recommendations.
Three things about your lot that Alameda County averages can't show:
We read public map data around Alameda County — soil, climate, flood, and parcel records. How we handle your address.
25+ data sources read at your address, not the Alameda County average
How we know this about Alameda County
The datasets: hardiness from the USDA ARS Plant Hardiness Zone Map 2023, read at county grain; hard-freeze dates from NOAA 1991–2020 28°F normals at this county’s own record where one resolves, and the labelled statewide window where none does; soils from the USDA NRCS SSURGO survey, area-weighted across the county’s own map units; boundaries and acreage from US Census TIGER/Line 2025; the contamination and pesticide records from the federal sources named in their beats above. Where Alameda County carries no record of its own, the figure is inherited and labelled — the resolution ledger below names each.
Common questions about Alameda County
When does frost risk typically end in Alameda County?
The last hard freeze (28°F) in Alameda County typically lands around Jan 12, 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 2.
How long is the growing season in Alameda County?
Measured between 28°F hard freezes, Alameda County sees about 334 frost-free days — roughly Jan 12 through Dec 12, per NOAA 1991–2020 climate normals. Tender crops work a shorter one: nearer Feb 2 to Nov 28, about 299 days.
Is the soil safe to grow vegetables in Alameda County?
The federal record around Alameda County runs heavier than most — 11,350 documented sites, mostly Brownfields entries (9,842), the nearest Nitrate record about 0.7 miles out — so test the soil before planting food in the ground, and raised beds with clean imported soil grow well in the meantime. Even here, proximity to a documented site is information, not a diagnosis of any one yard; the contamination map shows exactly what's recorded and where.
Everything above is measured at Alameda County's scale — its 9b band and its 334-day season. Your yard writes its own version of Alameda County's numbers: we read soil, sun, drainage and frost at your exact address. Try it for 14 days — no card required.
Will It Grow Here?
Zone fit is the first question — each answer below reads California's frost window, season length, and soil profile against the plant's real requirements.
What this page reads at Alameda County’s own scale
9 of the readings below were taken at Alameda County's own scale — its own ~334-day span between 28°F freezes, the 3 most extensive soil series mapped here and 11,350 documented sites inside its boundary; one is borrowed from a wider read, named and linked below.
Measured here
- Alameda County's own USDA hardiness band, zones 9bUSDA PHZM 2023
- Alameda County's own 28°F hard-freeze dates and its ~334-day span between themNOAA 1991–2020 Climate Normals
- The soil order, drainage, surface pH, and the 3 most extensive named soil series mapped in Alameda CountyUSDA NRCS SSURGO
- 11,350 documented contamination sites inside the county boundary, distance-sorted from its center — the closest Nitrate record about 0.7 miles outFederal environmental registers
- Alameda County's boundary and the 471,973 acres inside itUS Census TIGER/Line 2025
- Which of 1,086 plants clear zones 9b and a ~334-day seasonGrowable Ground crop-matching engine
- Alameda County sitting wholly inside the Central California Foothills and Coastal MountainsUS EPA Level III Ecoregions
- Open occurrence records documented in Alameda County for a tracked speciesGBIF derived datasets (CC0 / CC BY 4.0)
- Which agricultural compounds go onto Alameda County farmland, and roughly how muchUSGS NAWQA EPest county estimates
Inherited from a wider read
- The growing challenges every California grower plans around — written at state scale, so they stay on the state guidefrom California
What this page can’t tell you
- How the season shifts across Alameda County — the ~334 days above is one reading at its centre; the 12 towns below each carry their owntowns in this county →
- The soil pH, drainage, sun hours, and frost pockets on any one lot among Alameda County's 471,973 acreswhy one lot differs from the next →
- Which of those 11,350 documented sites actually reaches your soil — that needs your address, the wind, and the groundwater directionhow we read the record →
- Where cold air settles, which slopes face the sun, and which way the wind runs on your own ground — none of it survives being averaged over Alameda Countyread your own land →