Vashon, Washington, sits in USDA hardiness zone 9a — a zone band wide enough that plant choice, not possibility, is the interesting question.
Growers here do well with kale, potato, garlic, and western red cedar — with the usual caveat that any single yard's soil, sun, and drainage cast the deciding vote.
Even in Vashon, 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 Vashon 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 Vashon — soil, climate, flood, and parcel records. How we handle your address.
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Vashon — the short answer
Vashon, Washington: USDA zone 9a, about 252 days between hard freezes, across 24K acres of town.
- USDA zone
- 9a
- USDA PHZM 2023
- Last hard freeze (28°F)
- Mar 14
- King County normal — NOAA 1991–2020, nearest to this town
- First hard freeze (28°F)
- Nov 21
- King County normal — NOAA 1991–2020, nearest to this town
- Days between freezes
- ~252
- King County normal — NOAA 1991–2020, nearest to this town
- Town area
- 24K 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 King County’s — the closest measured record, labelled as such rather than passed off as local.
Hardiness Zone Range
Zone 9a is Vashon's average, not your lot's — a low corner or a tree line moves it. Against Vashon's 252-day season, see what your own ground reads.
Soil varies lot by lot — soil types explained.
What this means for growing in Vashon
Each reading below is measured for Vashon itself — here is what it means for a garden here, and the move an experienced grower makes about it.
Season length
From county recordsVashon runs about 252 days between hard freezes (read from King County, the closest normal to Vashon) — 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
MeasuredVashon 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 Vashon is in
Vashon sits in the Puget Lowland — EPA Level III, inside the wider Marine West Coast Forest. That is read at Vashon's own centroid rather than borrowed from King County.
What Grows in Vashon
Plants matched to Vashon's USDA zones 9a, 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 Vashon?
Rarely: the season closes in stages, not all at once, and each stage has its crops. Cool-season crops can go in from around Feb 14; tender transplants wait until two to three weeks after the last 28°F hard freeze, which lands near Mar 14 (NOAA 1991–2020 climate normals); and from midsummer, planting counts back from the first fall freeze around Nov 21 — long-season crops need about 90 days of runway, quick greens only 30. A long window like this one runs successions deep into fall — and even its last weeks take quick greens and garlic.
What's on the federal record near Vashon
Closest first, within ~10 miles of Vashon. Listing isn't leaking, and distance isn't exposure.
- 22N/03E-07J01Nitrate · 0.5 mi
- VASHON SAND AND GRAVELUnderground Storage Tanks · 0.6 mi
- WILLIAMS HEATING INCUnderground Storage Tanks · 0.6 mi
- NIKE BATTERY S-61 MISSILEUnderground Storage Tanks · 0.7 mi
- LAIDLAW TRANSIT INCUnderground Storage Tanks · 0.7 mi
- VASHON ISLAND SCHOOL DIST BUSUnderground Storage Tanks · 0.7 mi
- HEIGHTS WATERPFAS · 0.9 mi
- WATER DISTRICT 19PFAS · 0.9 mi
- VASHON HIGH SCHOOLUnderground Storage Tanks · 0.9 mi
- Toomey/SorgeNitrate · 1.0 mi
- Vashon Allied ArtsUnderground Storage Tanks · 1.2 mi
- ENGELS REPAIR & TOWINGUnderground Storage Tanks · 1.2 mi
6 more sites are on the record inside the same radius. See them on the map
Measured from Vashon'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 Vashon.
Sources Checked
within ~10 miles of Vashon
Severity Distribution
within ~10 miles of Vashon
Highest-Severity Sites
A note from Gnorman
What an experienced grower watches for around here
In and around Vashon, two things run higher than the national average within ~10 miles of Vashon — Superfund (16 sites) and PFAS (10 sites). Knowing it is half the work — and it's nothing a thoughtful grower can't plan for.
Superfund: Superfund sites represent the most severe contamination in the federal system.
PFAS: PFAS (per- and polyfluoroalkyl substances) are called "forever chemicals" because they do not biodegrade.
Commission professional soil testing before any food production (test for heavy metals, VOCs, and SVOCs).
Test irrigation water source — this is the primary pathway for PFAS to reach garden crops.
Check your specific parcel in Vashon
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 Vashon average
Your land is one point inside Vashon
Everything above resolves to Vashon as a whole — one PHZM band, read across 24K acres, with hard-freeze dates borrowed from King 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 Vashon Average
Vashon Average
- ●USDA Zones 9a, averaged across Vashon
- ●One soil character for all of Vashon
- ●Frost dates read at Vashon's scale: Mar 14 to Nov 21
YOUR Parcel
- ✓Your exact zone, not Vashon's 9a
- ✓Your SSURGO soil type & pH
- ✓Your sun exposure, cast in 3D
See MY Growing Report
Read your specific parcel in Vashon
Pull a site-specific report for your exact address in Vashon, Washington — soil, sun, drainage, frost risk, and scored plant recommendations.
Three things about your lot that Vashon averages can't show:
We read public map data around Vashon — soil, climate, flood, and parcel records. How we handle your address.
25+ data sources read at your address, not the Vashon average
How we know this about Vashon
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 King 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 Vashon
When does frost risk typically end in Vashon?
The last hard freeze (28°F) in Vashon typically lands around Mar 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 Apr 4.
When is the first frost in Vashon?
The first hard freeze (28°F) in Vashon typically arrives around Nov 21, per NOAA 1991–2020 climate normals — the point tender summer crops finish. Lighter frosts run ahead of it, near Nov 7, so the watching starts about Oct 22 — about 252 days after the spring freeze cleared.
How long is the growing season in Vashon?
Measured between 28°F hard freezes, Vashon sees about 252 frost-free days — roughly Mar 14 through Nov 21, per NOAA 1991–2020 climate normals. Tender crops work a shorter one: nearer Apr 4 to Nov 7, about 217 days.
Is the soil safe to grow vegetables in Vashon?
The federal record around Vashon is a meaningful one — 1,149 documented sites, mostly Underground Storage Tanks entries (707), the nearest Nitrate record about 0.5 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 Vashon?
From about Oct 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 Nov 21 (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 21. Hardy greens and roots shrug off light frost and sweeten after it — leave them in.
Everything above is measured at Vashon's scale — its 9a band and its 252-day season. Your yard writes its own version of Vashon'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 Vashon’s own scale
4 of the readings below were taken at Vashon's own scale — the 23,656 acres it covers and 1,149 documented sites around it; 6 are borrowed from a wider read, named and linked below.
Measured here
- Vashon's own USDA hardiness band, zones 9aUSDA PHZM 2023
- 1,149 documented contamination sites on the federal record near Vashon, the closest Nitrate record about 0.5 miles out from the town centreFederal environmental registers
- Vashon's boundary and the 23,656 acres inside itUS Census TIGER/Line 2025
- The ecoregion at Vashon's own centroid, the Puget LowlandUS EPA Level III Ecoregions
Inherited from a wider read
- The 28°F hard-freeze dates — Vashon has no normal of its own, so its county's is the closest measured readfrom King County
- Soil character — no town-scale survey exists, so Vashon's 23,656 acres read through its county's SSURGO summaryfrom King County
- The candidate plant list — Washington's curated set, filtered to this zone band and re-ordered by how much margin each has herefrom Washington
- Growing-degree days and winter chill — measured county-wide only, so the county page carries themfrom King County
- The growing challenges every Washington grower plans around — written at state scale, so they stay on the state guidefrom Washington
- Butterfly and beetle records, and the farmland pesticide estimate — all published county-widefrom King County
What this page can’t tell you
- The soil pH, drainage, sun hours, and frost pockets on any one lot among Vashon's 23,656 acreswhy one lot differs from the next →
- Which side of Vashon you're on — a low spot frosts first and a south wall warms early, and one normal is being asked to speak for all 23,656 acresreading your own microclimate →
- How close that record sits to YOUR lot — the closest Nitrate record about 0.5 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 Vashon-wide figureread your own land →
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