Generally — Most Areas
eastern hemlock (zones 4-10) partially overlaps with Washington (4a-9a). It can grow in zones 4-9 within the state.
Your yard isn't the whole zone.
Washington spans zones 4a-9a, 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 eastern hemlock against your parcel's actual hardiness, soil, and sun.
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Zone Comparison
Eastern Hemlock Needs
- USDA Zones: 4-10
- Soil pH: 4.2 - 5.7
- Sun: Shade
- Frost-Free Days: 80+
Washington Has
- USDA Zones: 4a-9a
- Last Frost: Mar 1 - Jun 1
- First Frost: Sep 15 - Nov 15
- Annual Rainfall: 6-90 inches
- Common Soils: Volcanic ash, Silt loam (Palouse), Sandy loam
Plant Zone Range (zones 4-10)
Preferred Soil pH
Plant data: USDA PLANTS Database / plant_species_v5.csv. State data: USDA ARS PHZM 2023, NOAA Climate Normals, NRCS SSURGO.
When to Plant Eastern Hemlock in Washington
The frost window
Across Washington, the last spring frost clears between Mar 1 and Jun 1, and the first fall frost lands between Sep 15 and Nov 15 (NOAA Climate Normals 1991-2020). Counting from the latest last frost to the earliest first frost, that's a 106-day window you can count on — up to 259 days on a mild site in a kind year.
Frost hardiness
Eastern Hemlock is cold-hardy to -33°F (USDA PLANTS Database), so you can plant on the early side of Washington's window — even a few weeks before the final frost date.
Establishment timing
As a long-lived plant, eastern hemlock isn't racing the calendar to a harvest date. Plant it in spring once the last-frost window passes so roots settle in through the full season, or in early fall while the soil still holds summer warmth.
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
Zone compatibility says you can survive winter here. Whether the growing season is long enough — and warm enough — is a different question.
Frost-free days
Eastern Hemlock wants 80+ frost-free days; a typical Washington site sees ~130 (NOAA Climate Normals). That leaves a workable window — start indoors to bank time.
Chill hours
Eastern Hemlock requires ~800 chill hours (32-45°F dormancy window). Washington typically banks ~1950 chill hours per winter (MSU Extension method), which keeps this plant on track.
Climate aggregates derive from USDA NRCS county-level hardiness data + Cornell CALS Extension GDD-by-region tables + MSU Extension chill-hours-by-zone (1991-2020 NOAA Climate Normals baseline).
Soil + Drainage Fit
Eastern Hemlock prefers acidic soil (pH 4.2-5.7). Washington's volcanic ash can run on the acidic side, which often aligns well — confirm with a soil test before planting.
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.
Eastern Hemlock in Washington — Quick Answer
- Verdict: Generally — Most Areas
- Plant Zones: 4-10 (USDA PLANTS Database)
- State Zones: 4a-9a (USDA ARS PHZM 2023)
- Growing Season: Mar 1 - Jun 1 to Sep 15 - Nov 15 (NOAA Climate Normals)
What Else to Consider
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
Plant to your side of the Cascades, not to the state — your exact spot's rainfall decides the whole plan.
East side requires irrigation — no rain from June through September
With no summer rain, drip lines and deep mulch are the growing season — set them up before June.
Slug and root rot pressure on the wet west side
Raise the beds, bait the slugs, and water mornings only — the wet-side trio that keeps roots and leaves healthy; extension has the details.
Short seasons at elevation in the Cascades and northeast corners
In the short-season corners, fast varieties plus a cold frame or tunnel reliably close the gap.
Washington Cooperative Extension
For Washington-specific cultivar recommendations, planting calendars, and pest pressure for eastern hemlock, the canonical source is WSU Extension. Their fact sheets carry the local trial data we can't generalize across 50 states.
Is Eastern Hemlock native to Washington?
Eastern Hemlock is native to parts of the Lower 48, but the USDA PLANTS Database (accessed 2026-07-01) does not document a native range in Washington. It can still earn a place in a Washington garden — the zone comparison above tells you whether it will thrive.
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 Eastern Hemlock in Washington
When can I plant Eastern Hemlock in Washington?
Washington's last spring frost clears between Mar 1 and Jun 1, and the first fall frost lands between Sep 15 and Nov 15 (NOAA Climate Normals 1991-2020). Eastern Hemlock is a long-lived planting, so target spring just after your local last frost — or early fall while the soil holds warmth — and let it establish through the season.
What hardiness zone is Eastern Hemlock grown in across Washington?
Washington spans USDA hardiness zones 4a-9a (USDA ARS PHZM 2023). Eastern Hemlock carries a range of zones 4-10, 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 ~130 frost-free days per year (derived from NOAA Climate Normals 1991-2020). Eastern Hemlock needs 80+ frost-free days, so check whether your local microclimate runs above or below the state average before settling on a planting date.
Is Eastern Hemlock native to Washington?
Eastern Hemlock is native to parts of the Lower 48, but the USDA PLANTS Database (accessed 2026-07-01) does not document a native range in Washington. It can still earn a place in a Washington garden — the zone comparison above tells you whether it will thrive.
How should I amend the soil for Eastern Hemlock in Washington?
Eastern Hemlock prefers pH 4.2-5.7 (USDA PLANTS Database). Most Washington soils run mildly acidic to neutral; many sites land near this band naturally, and a soil test plus targeted sulfur or organic amendment closes any gap.
Will Eastern Hemlock actually grow on my specific land in Washington?
State-level zone + climate data is a sketch. A Growable Ground parcel report scores eastern hemlock 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 eastern hemlock against your parcel's exact soil, sun, drainage, and frost data — not zone averages.
Three things about your exact spot that zone averages miss:
We read public map data for this spot — soil, climate, flood, and parcel records. How we handle your address.
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