Conditional — Some Areas
rosemary (zones 8-10) reaches only part of Washington (4a-9b): zones 8-9 are in range, so where you are in the state decides it.
Rosemary in Washington — the short answer
Rosemary in Washington: hardy in zones 8–10, full sun, against a state median of ~208 frost-free days.
- Plant zones
- 8-10
- Manual horticultural correction (source not retained); NC State Extension and Missouri Botanical Garden, with the remaining rows from other published sources or Growable Ground compilation
- Washington zones
- 4a-9b
- USDA PHZM 2023
- Frost window
- Mar 16 - Apr 15 – Oct 24 - Nov 18
- NOAA RCC ACIS 1991-2020, 28°F
- Shortest county season
- 131 days
- NOAA Regional Climate Centers ACIS, 1991-2020, county 28°F killing freeze
- Days to maturity
- 90 days
- Growable Ground Plant Database
Plant data: Growable Ground Plant Database, compiled from FAO ECOCROP, USDA PLANTS and university Extension sources — per-field provenance varies and is published with the dataset.
Your yard isn't the whole zone.
Washington spans zones 4a-9b, but your yard sits in exactly one — and slope, tree cover, and cold-air pockets nudge it further. Enter your address and we'll score rosemary against your parcel's actual hardiness, soil, and sun.
We read public map data for this spot — soil, climate, flood, and parcel records. How we handle your address.
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Washington is not one climate
Washington’s winter-low ladder runs across 39 counties, from zone 6 in Ferry County to zone 9 in San Juan County. That is 30°F between the two counties’ average coldest night — the difference between rosemary overwintering in the ground and coming under cover.
The middle half of 39 counties runs 7–8.5 zones, with a median of 7 zones — a 3-zone span end to end.
Measured across 39 Washington counties. USDA PHZM 2023, per county. Quartiles are order statistics — every figure shown is a value a real county recorded, not an interpolation. Your own site sits somewhere inside this range; a parcel report resolves where.
Where in Washington Fits Best
Rosemary is rated for zones 8–10 — a cold floor USDA puts at 10 to 20°F. Against Washington’s 39 counties that band holds in 17 of them, and the line runs at Jefferson County (zone 8a), the coldest county still inside it.
Inside zones 8–10
17 counties
- Pacific County · zone 8a
- Snohomish County · zone 8a
- Thurston County · zone 8a
3 of 17 shown
Below the zone 8 floor
22 counties
- Ferry County · zone 6a
- Okanogan County · zone 6a
- Pend Oreille County · zone 6a
3 of 22 shown
Winter cold is the limit here — the same plant works in a container that comes under cover.
County hardiness zones: USDA Plant Hardiness Zone Map (PHZM) 2023, per county. A zone is a 10°F band of average annual extreme minimum temperature, so the floor above is the band the plant's rating denotes, not a single measured kill point. Slope, shelter and cold-air drainage routinely move a site half a zone either way from its county figure — which is the part only your address resolves.
Even within Washington's zones 4a-9b, county microclimates differ enough to change what thrives. These counties carry the closest zone match for rosemary (USDA PHZM 2023):
Zone Comparison
Rosemary Needs
- USDA Zones: 8-10
- Frost-Free Days: 120+
- Sun: Full Sun
- Mature size: 4 ft tall
- Picking window: ~120 days of harvest
- Drought tolerance: High
Washington Has
- USDA Zones: 4a-9b
- Last Hard Freeze (28°F): Mar 16 - Apr 15
- First Hard Freeze (28°F): Oct 24 - Nov 18
- Annual Rainfall: 6-90 inches
- Common Soils: Volcanic ash, Silt loam (Palouse), Sandy loam
Plant Zone Range (zones 8-10)
Preferred Soil pH
Plant data: Growable Ground Plant Database, compiled from FAO ECOCROP, USDA PLANTS, and university Extension sources — per-field provenance varies and is published with the dataset. State data: USDA ARS PHZM 2023, NOAA Climate Normals, NRCS SSURGO.
When to Plant Rosemary in Washington
The frost window
Across Washington, the last spring hard freeze (28°F) clears between Mar 16 and Apr 15, and the first fall hard freeze lands between Oct 24 and Nov 18 (NOAA Regional Climate Centers ACIS, 1991-2020). Counting from the latest last freeze to the earliest first freeze, that's a 192-day window you can count on — up to 247 days on a mild site in a kind year. That marks the hard freeze, not the last light frost, so tender transplants usually wait another 2-3 weeks.
When to start the seed
Those dates are when rosemary goes out, not when it starts. It is sown under cover about 10 weeks ahead, so counting back from Washington's late-side last freeze of Apr 15 is what fixes your sowing date — and a yard that clears frost earlier than the state's late date starts earlier still.
Winter standing
Rosemary overwinters from USDA zone 8 and warmer (NC State Extension Gardener Plant Toolbox; Missouri Botanical Garden Plant Finder), and Washington runs as cold as zone 4, so it does not survive winter in the ground here. It is a woody plant rather than a crop you resow each spring, so neither a fall establishment date nor a harvest countdown describes it in Washington — which is why this page gives neither. What it needs here is a way through winter, not a planting date.
Frost window: NOAA Climate Normals 1991-2020. Plant timing fields: Growable Ground Plant Database — frost-free days from FAO ECOCROP, days to harvest from university Extension production guides, and growing-degree-day and chill-hour minimums that are compilation estimates rather than published figures. Your site's own frost dates can run earlier or later than the state range — a parcel report pins them down.
Growing Season Fit
The zone check says rosemary survives winter in part of Washington, not across all of it. Whether the season is long enough — and warm enough — is a different question.
Frost-free days
Rosemary wants 120+ frost-free days; a typical Washington site sees ~208 (NOAA Regional Climate Centers ACIS, 1991-2020). That leaves comfortable headroom for succession planting.
Growing degree days
Rosemary needs ~2500 GDD (base 50°F) to ripen. The state median runs ~1740 GDD (from PRISM 1991-2020 climate normals), so Washington's typical season runs short on heat — pick a south-facing site and consider season extension.
GDD and chill-hour figures are computed from PRISM 1991-2020 monthly climate normals; frost-free days from NOAA Regional Climate Centers ACIS, 1991-2020. Each is the state median across its counties (P25/P75 span the within-state spread). Hardiness-zone range is USDA PHZM 2023.
Soil + Drainage Fit
Rosemary tolerates a wide pH range (pH 4.2-8.3) — 4.1 units, acid ground through alkaline — so soil acidity is rarely what limits it in Washington. A soil test is still worth having, but for what else it tells you about this site, not to clear this plant. It will grow across that whole span, but it does best between pH 5 and 6.5 — worth knowing before you decide whether a Washington soil test result is a problem or just a number. Drainage matters: this plant wants well (dry spells). If your Washington site is heavier clay or sits in a low spot, raised beds or amendment with compost solve it.
Plant pH requirements: FAO ECOCROP and USDA PLANTS, with the remaining rows from other published sources or Growable Ground compilation. Drainage: FAO ECOCROP, with the remaining rows from other published sources or Growable Ground compilation. Washington soil profile from USDA NRCS SSURGO. Site-specific verification: a 30-minute soil test from your local Extension lab.
Before you plant rosemary for food
Anything you grow to eat takes up what is in the ground it grows in, so what is on record near you is worth knowing before rosemary goes in. What follows is Washington’s documented federal record at state scale — a screening signal, not a soil test, and not a statement about any one lot.
Safe to Grow Here?
What the federal record shows across Washington — and how to grow with it.
We checked the federal record across Washington — 33,912 documented sites across 8 of the 9 source types we track.
The most significant on record: 329 Superfund sites. Sites tracked in EPA's Superfund program — from assessment-stage CERCLIS entries to confirmed National Priorities List cleanup sites.
Washington 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.
Severity Distribution
across Washington
Highest-Severity Sites
A note from Gnorman
What an experienced grower watches for around here
In and around Washington, Mining runs higher than the national average — 3,881 sites across Washington. It's not cause for alarm — it's worth knowing, and there's a sensible way to grow around it.
Mining: Mining sites — both historic and active — can leach heavy metals (arsenic, lead, cadmium, mercury) into soil and water for centuries after operations cease.
Test soil for heavy metals (lead, arsenic, cadmium, mercury) — this is essential near any mining site.
Sources: EPA, USGS — 1.8M documented sites tracked nationwide across 9 federal source types.
What Else to Consider for Rosemary in Washington
Zone compatibility tells you about winter cold survival — but Washington growers also need to think about:
Extreme rain divide: 90+ inches west, 6 inches east of Cascades
East side requires irrigation — no rain from June through September
Slug and root rot pressure on the wet west side
Short seasons at elevation in the Cascades and northeast corners
What to actually do about these — and the constraints that apply to every Washington grower, not just rosemary — is covered on the Washington growing guide.
Timing shifts within Washington
Rosemary needs about 120 days of frost-free season to complete its cycle. Even Whatcom County — Washington’s shortest season at 131 frost-free days — clears that by 11 days, so season length isn’t the constraint anywhere in Washington. What varies is your own parcel.
Across Washington’s 39 counties the frost-free season runs from 131 days in Whatcom County to 300 days in San Juan County — a spread of 169 days, which is why a single statewide planting date misleads. The median Washington county sees 208 frost-free days, leaving rosemary about 88 days of slack on a typical parcel — room for a second sowing where the season runs long.
County last-freeze dates and frost-free day counts: NOAA Regional Climate Centers ACIS (1991-2020), county 28°F freeze (earlier than the folk 32°F "last frost"). Rosemary's 120-day requirement: USDA PLANTS / Growable Ground plant database (minimum frost-free days). A parcel report resolves your address's own frost dates.
Pollinator + Wildlife Value
Rosemary draws honeybees and native bees (high value, Growable Ground Plant Database). Planting it near vegetable beds can lift fruit set on neighboring crops. Outdoors, rosemary can only work that bloom inside Washington's frost window — roughly 208 days, opening after the last 28°F freeze (Mar 16 - Apr 15) and closing at the first (Oct 24 - Nov 18), per NOAA Regional Climate Centers ACIS, 1991-2020. Deer pressure is meaningful across much of Washington; rosemary is listed as deer-resistant (USDA PLANTS Database), which makes it a safer pick for unfenced sites. Our deer & wildlife guide carries the full deer-resistant list and how to protect the rest.
Washington Cooperative Extension
For Washington-specific cultivar recommendations, planting calendars, and pest pressure for rosemary, the canonical source is WSU Extension. Their fact sheets carry the local trial data we can't generalize across 50 states.
Common Questions About Growing Rosemary in Washington
When can I plant Rosemary in Washington?
Washington's last spring hard freeze (28°F) clears between Mar 16 and Apr 15, and the first fall hard freeze lands between Oct 24 and Nov 18 (NOAA Regional Climate Centers ACIS, 1991-2020). Rosemary overwinters only from USDA zone 8 and warmer, and Washington runs as cold as zone 4, so it does not survive winter in the ground here — the question for Washington growers is how to carry it through winter under cover, not which week to plant it.
What hardiness zone is Rosemary grown in across Washington?
Washington spans USDA hardiness zones 4a-9b (USDA ARS PHZM 2023). Rosemary carries a range of zones 8-10, so the overlap zones are where outdoor growing is most reliable.
How many frost-free days does a typical Washington site have?
A typical Washington site sees ~208 frost-free days per year (derived from NOAA Regional Climate Centers ACIS, 1991-2020). Rosemary needs 120+ frost-free days, so check whether your local microclimate runs above or below the state average before settling on a planting date.
How should I amend the soil for Rosemary in Washington?
Rosemary tolerates pH 4.2-8.3 and well (dry spells) drainage (FAO ECOCROP). That is a 4.1-unit span, acid ground through alkaline, so pH is rarely what limits this plant on a Washington site — amend for drainage and organic matter first.
Will Rosemary actually grow on my specific land in Washington?
State-level zone + climate data is a sketch. A Growable Ground parcel report scores rosemary against your address's exact soil pH, drainage, sun, and frost-date data drawn from USDA SSURGO, NOAA, and PRISM — not state averages.
Check your specific parcel in Washington
State-level data is a sketch. Your Growable Ground report scores rosemary against your parcel's exact soil, sun, drainage, and frost data — not zone averages.
Three things about your lot that Washington rosemary averages can't show:
We read public map data around Washington — soil, climate, flood, and parcel records. How we handle your address.
25+ data sources read at your address, not the Washington rosemary average
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