Portola Valley, California, sits in USDA hardiness zone 10a — enough range to grow cool-season vegetables, hardy fruit, and warm-season crops that mature before the first hard frost.
Expect okra, meyer lemon, california poppy, and artichoke to be strong candidates here; the deciding factors on any one parcel stay local — soil, sun, and drainage.
Even in Portola 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 Portola 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 Portola Valley — soil, climate, flood, and parcel records. How we handle your address.
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Portola Valley — the short answer
Portola Valley, California: USDA zone 10a, about 342 days between hard freezes, across 6K acres of town.
- USDA zone
- 10a
- USDA PHZM 2023
- Last hard freeze (28°F)
- Jan 14
- NOAA 1991–2020 Climate Normals, 28°F — this town
- First hard freeze (28°F)
- Dec 22
- NOAA 1991–2020 Climate Normals, 28°F — this town
- Days between freezes
- ~342
- NOAA 1991–2020 Climate Normals, 28°F — this town
- Town area
- 6K 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 10a is Portola Valley's average, not your lot's — a low corner or a tree line moves it. Against Portola Valley's 342-day season, see what your own ground reads.
Soil varies lot by lot — soil types explained.
What this means for growing in Portola Valley
Each reading below is measured for Portola Valley itself — here is what it means for a garden here, and the move an experienced grower makes about it.
Season length
MeasuredPortola Valley runs about 342 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
MeasuredPortola 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 Portola Valley is in
Portola Valley sits in the Coast Range — EPA Level III, inside the wider Marine West Coast Forest. That is read at Portola Valley's own centroid rather than borrowed from San Mateo County.
What Grows in Portola Valley
Every plant below cleared Portola Valley's own zone 10a and its 342-day season. Each card opens that plant's California profile. How we score.
Is it too late to plant in Portola Valley?
Rarely: the season closes in stages, not all at once, and each stage has its crops. 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 14 (NOAA 1991–2020 climate normals); and from midsummer, planting counts back from the first fall freeze around Dec 22 — long-season crops need about 90 days of runway, quick greens only 30. With almost year-round growing weather, timing is about heat and rainfall more than frost — some bench is always in play.
Documented around Portola Valley
Spotted lanternfly documented 26 miles from Portola Valley, first recorded 2023. What to watch for.
What's on the federal record near Portola Valley
Closest first, within ~10 miles of Portola Valley. Listing isn't leaking, and distance isn't exposure.
- MAT PEL BUILDERSBrownfields · 0.6 mi
- THE SEQUOIAS PORTOLA VALLEYBrownfields · 0.8 mi
- MARK & KAREN PERLROTHBrownfields · 1.1 mi
- SAN MATEO COUNTYBrownfields · 1.2 mi
- CALIFORNIA WATER SERVICE COMPANY - BG 32Brownfields · 1.2 mi
- SF40XC005 - CAL TRANSBrownfields · 1.3 mi
- FACEBOOK, INC.Brownfields · 1.3 mi
- WILBAK CORPORATION DBA VILLAGE SQUARE VETERINARY HOSPITALBrownfields · 1.3 mi
- WOODSIDE PRIORY SCHOOLBrownfields · 1.3 mi
- GEOFFREY BALDWINBrownfields · 1.3 mi
- PORTOLA VALLEY FUELUnderground Storage Tanks · 1.4 mi
- RON RAMIES AUTOMOTIVE INCBrownfields · 1.4 mi
6 more sites are on the record inside the same radius. See them on the map
Measured from Portola 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 Portola Valley.
Sources Checked
within ~10 miles of Portola Valley
Severity Distribution
within ~10 miles of Portola Valley
Highest-Severity Sites
A note from Gnorman
What an experienced grower watches for around here
In and around Portola Valley, Brownfields runs higher than the national average — 2,954 sites within ~10 miles of Portola Valley. 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 Portola 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 Portola Valley average
Your land is one point inside Portola Valley
Everything above resolves to Portola Valley as a whole — one PHZM band and one 28°F frost record, read across 6K 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 Portola Valley Average
Portola Valley Average
- ●USDA Zones 10a, averaged across Portola Valley
- ●One soil character for all of Portola Valley
- ●Frost dates read at Portola Valley's scale: Jan 14 to Dec 22
YOUR Parcel
- ✓Your exact zone, not Portola Valley's 10a
- ✓Your SSURGO soil type & pH
- ✓Your sun exposure, cast in 3D
See MY Growing Report
Read your specific parcel in Portola Valley
Pull a site-specific report for your exact address in Portola Valley, California — soil, sun, drainage, frost risk, and scored plant recommendations.
Three things about your lot that Portola Valley averages can't show:
We read public map data around Portola Valley — soil, climate, flood, and parcel records. How we handle your address.
25+ data sources read at your address, not the Portola Valley average
How we know this about Portola Valley
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 Portola Valley’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 Portola Valley
When does frost risk typically end in Portola Valley?
The last hard freeze (28°F) in Portola Valley typically lands around Jan 14, 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 4.
When is the first frost in Portola Valley?
The first hard freeze (28°F) in Portola Valley typically arrives around Dec 22, per NOAA 1991–2020 climate normals — the point tender summer crops finish. Lighter frosts run ahead of it, near Dec 8, so the watching starts about Nov 22 — about 342 days after the spring freeze cleared.
How long is the growing season in Portola Valley?
Measured between 28°F hard freezes, Portola Valley sees about 342 frost-free days — roughly Jan 14 through Dec 22, per NOAA 1991–2020 climate normals. Tender crops work a shorter one: nearer Feb 4 to Dec 8, about 307 days.
Is the soil safe to grow vegetables in Portola Valley?
The federal record around Portola Valley runs heavier than most — 3,319 documented sites, mostly Brownfields entries (2,954), the nearest Brownfields record about 0.6 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.
How do I protect my plants from frost in Portola Valley?
From about Nov 22 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 22 (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 22. Hardy greens and roots shrug off light frost and sweeten after it — leave them in.
Everything above is measured at Portola Valley's scale — its 10a band and its 342-day season. Your yard writes its own version of Portola 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 Portola Valley’s own scale
7 of the readings below were taken at Portola Valley's own scale — its own ~342-day season between 28°F freezes, the 5,813 acres it covers and 3,319 documented sites around it; 4 are borrowed from a wider read, named and linked below.
Measured here
- Portola Valley's own USDA hardiness band, zones 10aUSDA PHZM 2023
- Portola Valley's own 28°F hard-freeze dates, about Jan 14 and Dec 22 and the ~342-day span between themNOAA 1991–2020 Climate Normals
- 3,319 documented contamination sites on the federal record near Portola Valley, the closest Brownfields record about 0.6 miles out from the town centreFederal environmental registers
- Portola Valley's boundary and the 5,813 acres inside itUS Census TIGER/Line 2025
- Which of 1,086 plants clear zones 10a and a ~342-day seasonGrowable Ground crop-matching engine
- The ecoregion at Portola Valley's own centroid, the Coast RangeUS EPA Level III Ecoregions
- A documented spotted-lanternfly record within reach of Portola Valleylydemapr (De Bona & Helmus), 10 km survey lattice
Inherited from a wider read
- Soil character — no town-scale survey exists, so Portola Valley's 5,813 acres read through its county's SSURGO summaryfrom San Mateo County
- Growing-degree days and winter chill — measured county-wide only, so the county page carries themfrom San Mateo 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 Mateo County
What this page can’t tell you
- The soil pH, drainage, sun hours, and frost pockets on any one lot among Portola Valley's 5,813 acreswhy one lot differs from the next →
- Which side of Portola 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 5,813 acresreading your own microclimate →
- How close that record sits to YOUR lot — the closest Brownfields record about 0.6 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 Portola Valley-wide figureread your own land →