King County, in Washington, sits in USDA hardiness zone 8b — room for a real mix of vegetables, fruit, and perennials matched to the local frost calendar.
On paper, cabbage, fig, california poppy, and collard greens all suit these conditions — on the ground, soil, sun, and drainage make the final call.
King County lies within the Pacific Northwest — a regional growing area with its own character.
Grounded in USDA PHZM 2023 · Growable Ground suitability scoring · NOAA 1991–2020 Climate Normals
King County holds more than one microclimate.
Soils and elevations shift across King 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 King County — soil, climate, flood, and parcel records. How we handle your address.
No card required · your full report in seconds
King County — the short answer
King County, Washington: USDA zone 8b, about 252 days between hard freezes, across 1.4M acres.
- USDA zone
- 8b
- USDA PHZM 2023
- Last hard freeze (28°F)
- Mar 14
- NOAA 1991–2020 Climate Normals, 28°F
- First hard freeze (28°F)
- Nov 21
- NOAA 1991–2020 Climate Normals, 28°F
- Days between freezes
- ~252
- NOAA 1991–2020 Climate Normals, 28°F
- County area
- 1.4M 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 8b is King County's average, not your lot's — a low corner or a tree line moves it. Against King County's 252-day season, see what your own ground reads.
Heat in King County
Across a year, King County accumulates about 1,291 growing degree days above 50°F, about 422 fewer than the middle Washington county — ahead of 10 of Washington’s 39 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.
Grounded in PRISM Climate Group, Oregon State University — 1991–2020 monthly normals
Soil in King County
Across King County, the ground is predominantly Spodosols, where Alderwood, Playco, and Pitcher are the most extensive named soil series. The soil is generally well drained with a gravelly sandy loam surface. Topsoil pH runs about 5.0–5.8, strongly acidic. Rainfall drains through hydrologic group B soils.
Soil order
Spodosols
Drainage
Well drained
Prime farmland
4%
Hydric soils
5%
Soil still varies lot by lot — soil types explained.
How the ground varies across King County
The USDA soil survey maps 41% of King County as well drained — but another 48% drains differently: 30% moderately well drained, 8% somewhat excessively drained.
Alderwood is the most extensive named soil at 18% of mapped acres, then Playco (8%) and Pitcher (5%).
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 King County
Each reading below is measured for King 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 King County are well drained, in hydrologic group B — 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 King County runs about pH 5.0–5.8, on the acidic side.
Blueberries, potatoes, and rhododendrons thrive in it, but most vegetables start locking out nutrients below about pH 6.0 and grow pale and stunted no matter how much you feed them.
A measured lime application raises pH for the crops that need it — but test first, because the right rate depends on your own soil, not the county average.
USDA NRCS SSURGO
Season length
MeasuredKing County runs about 252 days between hard freezes — 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
MeasuredKing County sits in USDA hardiness zone 8b.
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 King County is in
King County spans 3 EPA Level III ecoregions — Puget Lowland (45%), North Cascades (32%) and Cascades (23%). Which one your land falls in changes what grows wild there and how the ground behaves, and a county-wide answer cannot tell you which.
What Grows in King County
We scored all 1,086 plants against King County's own USDA zone 8b and its own 252-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 Washington profile.
Is it too late to plant in King County?
Too late for some crops, right on time for others — a growing season is a sequence, not a deadline. 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.
Documented around King County
- monarch butterfly5 documented records
Sighting records, so they follow observers as much as insects.
What gets applied to farmland in King County
USGS estimates 1,498 lb of Glyphosate on King County farmland in 2019, its largest by weight, ahead of 2,4-d (1,021 lb) and Metolachlor-s (727 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 King County — and how to grow with it.
We checked the federal record across King County — 6,301 documented sites across 8 of the 9 source types we track.
The most significant on record: 37 Superfund sites. Sites tracked in EPA's Superfund program — from assessment-stage CERCLIS entries to confirmed National Priorities List cleanup sites.
King 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 King County
Closest first, across King County. Listing isn't leaking, and distance isn't exposure.
- RATTLESNAKE MOUNTAIN MICROWAVE STATIONUnderground Storage Tanks · 1.5 mi
- A E DOWNS MANUFACTURING PLANTUnderground Storage Tanks · 1.5 mi
- RATTLESNAKE B530330/RTLGWAQ2710Underground Storage Tanks · 1.6 mi
- G & S SERVICESUnderground Storage Tanks · 1.8 mi
- Mt Si ShellUnderground Storage Tanks · 1.9 mi
- MOUNT SI GOLF COURSE INCUnderground Storage Tanks · 1.9 mi
- SAFEWAY FUEL 1528Underground Storage Tanks · 1.9 mi
- SAFEWAY 1528Brownfields · 2.0 mi
- NORTH BEND B530350/NBNDWA01Underground Storage Tanks · 2.0 mi
- CASCADE AUTOVON COMPANYUnderground Storage Tanks · 2.0 mi
- NORTH BENDUnderground Storage Tanks · 2.0 mi
- PUBLIC HOSPITAL DISTRICT 4 KING COUNTYUnderground Storage Tanks · 2.0 mi
6 more sites are on the record inside the same radius. See them on the map
Measured from King 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 King County.
Severity Distribution
across King County
Highest-Severity Sites
A note from Gnorman
What an experienced grower watches for around here
In and around King County, Underground Storage Tanks runs higher than the national average — 3,922 sites across King County. It's not cause for alarm — it's worth knowing, and there's a sensible way to grow around it.
Underground Storage Tanks: Underground storage tanks are the single most common source of soil contamination near homes and gardens.
Use raised beds with imported soil — this eliminates the primary soil-contact pathway.
Check your specific parcel in King 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 King County average
Your land is one point inside King County
Everything above resolves to King County as a whole — one PHZM band and one county frost record, read across 1.4M 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 King County Average
King County Average
- ●USDA Zones 8b, averaged across King County
- ●One soil character for all of King County
- ●Frost dates read at King County's scale: Mar 14 to Nov 21
YOUR Parcel
- ✓Your exact zone, not King County's 8b
- ✓Your SSURGO soil type & pH
- ✓Your sun exposure, cast in 3D
See MY Growing Report
Read your parcel in King County
Pull a site-specific report for your exact address in King County, Washington — soil, sun, drainage, frost risk, and scored plant recommendations.
Three things about your lot that King County averages can't show:
We read public map data around King County — soil, climate, flood, and parcel records. How we handle your address.
25+ data sources read at your address, not the King County average
How we know this about King 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 King County carries no record of its own, the figure is inherited and labelled — the resolution ledger below names each.
Common questions about King County
When does frost risk typically end in King County?
The last hard freeze (28°F) in King County 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.
How long is the growing season in King County?
Measured between 28°F hard freezes, King County 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 King County?
The federal record around King County runs heavier than most — 6,301 documented sites, mostly Underground Storage Tanks entries (3,922), the nearest Underground Storage Tanks record about 1.5 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 King County's scale — its 8b band and its 252-day season. Your yard writes its own version of King 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 Washington's frost window, season length, and soil profile against the plant's real requirements.
What this page reads at King County’s own scale
9 of the readings below were taken at King County's own scale — its own ~252-day span between 28°F freezes, the 3 most extensive soil series mapped here and 6,301 documented sites inside its boundary; one is borrowed from a wider read, named and linked below.
Measured here
- King County's own USDA hardiness band, zones 8bUSDA PHZM 2023
- King County's own 28°F hard-freeze dates and its ~252-day span between themNOAA 1991–2020 Climate Normals
- The soil order, drainage, surface pH, and the 3 most extensive named soil series mapped in King CountyUSDA NRCS SSURGO
- 6,301 documented contamination sites inside the county boundary, distance-sorted from its center — the closest Underground Storage Tanks record about 1.5 miles outFederal environmental registers
- King County's boundary and the 1,354,079 acres inside itUS Census TIGER/Line 2025
- Which of 1,086 plants clear zones 8b and a ~252-day seasonGrowable Ground crop-matching engine
- The 3 ecoregions King County spans, Puget Lowland the largestUS EPA Level III Ecoregions
- Open occurrence records documented in King County for a tracked speciesGBIF derived datasets (CC0 / CC BY 4.0)
- Which agricultural compounds go onto King County farmland, and roughly how muchUSGS NAWQA EPest county estimates
Inherited from a wider read
- The growing challenges every Washington grower plans around — written at state scale, so they stay on the state guidefrom Washington
What this page can’t tell you
- How the season shifts across King County — the ~252 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 King County's 1,354,079 acreswhy one lot differs from the next →
- Which of those 6,301 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 King Countyread your own land →