Yes — Strong Match
sweet pea (zones 2-10) covers every zone Washington contains (4a-9b), so hardiness is not what limits it anywhere in the state.
Your yard isn't the whole zone.
Sweet Pea is grown as an annual, so your winter zone isn't the deciding factor — your frost-free window is. A typical Washington site runs ~208 frost-free days, but that is a state median, not your yard: slope, trees, and low spots move the last-frost date across a single parcel. Enter your address and we'll score sweet pea against your land's actual frost dates, sun, and soil.
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Zone Comparison
Sweet Pea Needs
- USDA Zones: 2-10
- Frost-Free Days: 150+
- Sun: Full Sun
- Mature size: 6 ft tall
- Picking window: ~60 days of harvest
- Drought tolerance: Low
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 2-10)
Preferred Soil pH
Plant data: USDA PLANTS Database / Growable Ground plant catalog. State data: USDA ARS PHZM 2023, NOAA Climate Normals, NRCS SSURGO.
When to Plant Sweet Pea 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.
Frost tenderness
Sweet Pea is frost-tender — its listed minimum temperature is 39.2°F (USDA PLANTS Database) — so set plants out two to three weeks PAST your local last hard freeze, not on it and not on the state's earliest date. The 28°F marker above is when killing freezes stop, not when light frost does.
When to start the seed
Those dates are when sweet pea goes out, not when it starts. It is sown under cover about 6 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.
Days to maturity vs. the window
At 65 days to maturity (USDA PLANTS Database), counting from the last hard freeze it ripens with 127 days to spare even in Washington's tightest freeze scenario — room for a later start or a second sowing.
Timing tuned to sub-state frost dates — Whatcom County, not the statewide average.
Frost window: NOAA Climate Normals 1991-2020. Plant timing fields: USDA PLANTS Database. 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 sweet pea survives winter here. Whether the season is long enough — and warm enough — is a different question.
Frost-free days
Sweet Pea wants 150+ frost-free days; a typical Washington site sees ~208 (NOAA Regional Climate Centers ACIS, 1991-2020). That leaves a workable window — start indoors to bank time.
Growing degree days
Sweet Pea needs ~500 GDD (base 50°F) to ripen. The state median runs ~1740 GDD (from PRISM 1991-2020 climate normals), so Washington's typical season clears that easily.
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
Sweet Pea likes near-neutral soil (pH 6-8). That's the common-ground band across Washington's volcanic ash and silt loam (palouse) — a soil test confirms it for your site. It will grow across that whole span, but it does best between pH 6.5 and 7.5 — 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.
Your land, not the state average
Washington's soils run mostly silt loam, but SSURGO maps the series, texture, and drainage under your exact parcel. Sweet Pea needs about 7 inches of workable depth, so it is that horizon — not the surface — you are testing for. That map unit, not the state average, decides how sweet pea performs.
Check your parcel → Source: USDA NRCS SSURGO.
Plant pH and drainage requirements from USDA PLANTS Database. Washington soil profile from USDA NRCS SSURGO. Site-specific verification: a 30-minute soil test from your local Extension lab.
Sweet Pea in Washington — Quick Answer
- Verdict: Yes — Strong Match
- Plant Zones: 2-10 (USDA PLANTS Database)
- State Zones: 4a-9b (USDA ARS PHZM 2023)
- Growing Season: 28°F hard freezes about Mar 16 - Apr 15 to Oct 24 - Nov 18 (NOAA Regional Climate Centers ACIS, 1991-2020)
- Days to Maturity: 65 days
What Else to Consider for Sweet Pea 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
Growing sweet pea here specifically
Sweet Pea needs pH 6.0–8.0; Washington's dominant silt loam soils may or may not deliver that, so your parcel's SSURGO map unit is the real test.
Start with a soil test on your own ground and adjust pH and texture to fit sweet pea's 6.0–8.0 range. How to handle it →
What to actually do about these — and the constraints that apply to every Washington grower, not just sweet pea — is covered on the Washington growing guide.
Timing shifts within Washington
Washington isn't one climate. In Whatcom County, the last hard freeze (28°F) holds until about May 29 — roughly 54 days later than the recorded state median — so plant sweet pea to your county's window, not the statewide date.
Sweet Pea needs about 150 days of frost-free season to complete its cycle. 38 of Washington’s 39 counties give it that outright. The tightest that does is Chelan County at 158 frost-free days — 8 to spare. Below that line you are transplanting or extending the season, not direct-sowing.
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 sweet pea about 58 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"). Sweet Pea's 150-day requirement: USDA PLANTS / Growable Ground plant database (minimum frost-free days). A parcel report resolves your address's own frost dates.
Where in Washington Fits Best
Even within Washington's zones 4a-9b, county microclimates differ enough to change what thrives. These counties carry the closest zone match for sweet pea (USDA PHZM 2023):
Pollinator + Wildlife Value
Sweet Pea draws honeybees and native bees (moderate value, Growable Ground Plant Database). Planting it near vegetable beds can lift fruit set on neighboring crops. Outdoors, sweet pea 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.
Good to Know Before You Plant Sweet Pea
Sweet Pea is listed as toxic to dogs, cats (seeds, pods) at a moderate level (ASPCA). Most listed plants only cause brief upset — a raised bed or a fenced corner usually keeps curious pets clear. Worth knowing for placement: in Washington this is a one-season plant and the first hard freeze (Oct 24 - Nov 18) takes it down, so the exposure above is a summer-long one rather than something standing in the bed all year.
Recommended Sweet Pea Varieties for Washington
Washington publishes no state variety trial for sweet pea, so we won't invent a "best for Washington" list. Choose types rated to your USDA hardiness zone (4a-9b), and confirm winter survival and drainage against your own parcel.
Washington Cooperative Extension
For Washington-specific cultivar recommendations, planting calendars, and pest pressure for sweet pea, the canonical source is WSU Extension. Their fact sheets carry the local trial data we can't generalize across 50 states.
Is Sweet Pea native to Washington?
No — the USDA PLANTS Database lists Sweet Pea as introduced rather than native in the Lower 48, so it is not part of Washington's native flora. It grows here as a garden plant; pairing it with a few Washington natives keeps local pollinators fed too.
Looking for plants that belong here? The Washington growing guide lists USDA-documented natives for the state.
Native-range data: USDA PLANTS Database state-distribution records, accessed 2026-07-01.
Common Questions About Growing Sweet Pea in Washington
When can I plant Sweet Pea 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). Sweet Pea is frost-tender — its listed minimum temperature is 39.2°F (USDA PLANTS Database) — so wait two to three weeks past your site's last hard freeze, when light frost has also stopped, before planting out.
Can Sweet Pea mature before first frost in Washington?
Yes — Sweet Pea matures in 65 days (USDA PLANTS Database), and Washington's dependable hard-freeze-free window runs 192 days (NOAA Regional Climate Centers ACIS, 1991-2020), leaving 127 days of margin. Plant once the last hard freeze has passed — two to three weeks later for anything tender — and it ripens ahead of the first fall freeze.
What hardiness zone is Sweet Pea grown in across Washington?
Washington spans USDA hardiness zones 4a-9b (USDA ARS PHZM 2023). Sweet Pea carries a range of zones 2-10, 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). Sweet Pea needs 150+ frost-free days, so check whether your local microclimate runs above or below the state average before settling on a planting date. In cooler counties like Whatcom, the freeze-free season runs shorter than the state average, so verify your own county's window.
Is Sweet Pea native to Washington?
No — the USDA PLANTS Database lists Sweet Pea as introduced rather than native in the Lower 48, so it is not part of Washington's native flora. It grows here as a garden plant; pairing it with a few Washington natives keeps local pollinators fed too.
How should I amend the soil for Sweet Pea in Washington?
Sweet Pea prefers pH 6-8 and well (dry spells) drainage (FAO ECOCROP). That sits in the common-ground band across Washington soils — a 30-minute soil test from a local Extension lab confirms it for your specific site.
Will Sweet Pea actually grow on my specific land in Washington?
State-level zone + climate data is a sketch. A Growable Ground parcel report scores sweet pea 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 sweet pea against your parcel's exact soil, sun, drainage, and frost data — not zone averages.
Three things about your lot that Washington sweet pea 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 sweet pea average
Explore More
Growing guides for sweet pea
Analysis by the Growable Ground research team, grounded in USDA PLANTS, USDA NRCS SSURGO, NOAA Climate Normals (1991-2020), and named Cooperative Extension sources. How we know →
Cite this dataset
Kirchick, M. (2026). Growable Ground Plant Database [Data set]. Zenodo. https://doi.org/10.5281/zenodo.21435643
Licensed CC BY-NC 4.0. DOI 10.5281/zenodo.21435643
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