Unlikely — Zone Mismatch
sisal hemp (zones 10-11) does not overlap with Washington's zone range (4a-9b). Growing outdoors is unlikely without significant protection.
Sisal Hemp in Washington — the short answer
Sisal Hemp in Washington: hardy in zones 10–11, full sun, against a state median of ~208 frost-free days.
- Plant zones
- 10-11
- Hardy to zone 9b: Tropical Plants Database (Useful Tropical Plants) lists -5 °C, converted to zone 9b, checked Oct 2026. The source rates it slightly hardier than our range. Ceiling: not verified.
- 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
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 has its own microclimate — slope, trees, and low spots shift frost and sun across a single parcel. Enter your address and we'll score sisal hemp against your land's actual soil, sun, and frost.
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
A single Washington answer averages 39 counties whose growing seasons are 169 days apart — from 131 frost-free days in Whatcom County to 300 in San Juan County. Which end of that your land sits nearer changes what sisal hemp can finish before the first hard freeze.
The middle half of 39 counties runs 192–248 days, with a median of 208 days — a 169-day span end to end.
Measured across 39 Washington counties. NOAA Regional Climate Centers ACIS, 1991-2020, county 28°F killing freeze. 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 Sisal Hemp Stands in Washington
Sisal Hemp is rated for zones 10–11 — a cold floor USDA puts at 30 to 40°F. No Washington county sits inside it, so in open ground this is a grown-under-cover plant here rather than a bed plant — which is a statement about Washington winters, not about sisal hemp.
Below the zone 10 floor
39 counties
- Ferry County · zone 6a
- Okanogan County · zone 6a
- Pend Oreille County · zone 6a
3 of 39 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.
Zone Comparison
Sisal Hemp Needs
- USDA Zones: 10-11
- Frost-Free Days: 150+
- Sun: Full SunWe haven't confirmed this against a published source yet.
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 10-11)
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 Sisal Hemp 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 hardiness
Sisal Hemp takes cold down to about 23°F before a freeze kills it (FAO ECOCROP), so you can plant on the early side of Washington's window — even a few weeks before the final hard freeze. That is the point where cold damages growing tissue, not a winter-survival floor — an established perennial comes through far colder while dormant, which is what its hardiness zone tells you.
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 sisal hemp does not survive a Washington winter in the ground. The season figures below measure a different question — whether it could finish a season here at all — and they only bear on Washington under protection.
Frost-free days
Sisal Hemp 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.
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
Sisal Hemp likes near-neutral soil (pH 5.5-8). 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 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, a raised bed lifts the roots above wet ground, or work in compost. Drainage need: We haven't confirmed this against a published source yet.
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.
What Else to Consider for Sisal Hemp 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 sisal hemp — is covered on the Washington growing guide.
Timing shifts within Washington
Sisal Hemp 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 sisal hemp 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"). Sisal Hemp's 150-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
Sisal Hemp draws native bees and moths (moderate value). Planting it near vegetable beds can lift fruit set on neighboring crops. Outdoors, sisal hemp 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. Pollinator value: We haven't confirmed this against a published source yet.
Washington Cooperative Extension
For Washington-specific cultivar recommendations, planting calendars, and pest pressure for sisal hemp, the canonical source is WSU Extension. Their fact sheets carry the local trial data we can't generalize across 50 states.
Is Sisal Hemp native to Washington?
No — the USDA PLANTS Database lists Sisal Hemp 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 plants that USDA PLANTS records growing in Washington and that Kew and NatureServe Explorer both list in its native range, leaving out any that NatureServe flags as exotic there or that our audit holds.
State records: USDA PLANTS Database state-distribution data (presence, not state-level nativity), accessed 2026-10-19.
Common Questions About Growing Sisal Hemp in Washington
When can I plant Sisal Hemp 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). Sisal Hemp takes cold to about 23°F before a freeze kills it (FAO ECOCROP — the point where cold damages growing tissue, not a winter-survival floor), so plant on the early side of that window — even ahead of the final hard freeze.
What hardiness zone is Sisal Hemp grown in across Washington?
Washington spans USDA hardiness zones 4a-9b (USDA ARS PHZM 2023). Sisal Hemp is listed for zones 10-11, which do not overlap them, so there is no zone in Washington where this page can call outdoor growing reliable. A parcel report resolves your own address's zone.
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). Sisal Hemp needs 150+ frost-free days, so check whether your local microclimate runs above or below the state average before settling on a planting date.
Is Sisal Hemp native to Washington?
No — the USDA PLANTS Database lists Sisal Hemp 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 Sisal Hemp in Washington?
Sisal Hemp prefers pH 5.5-8 and well (dry spells) drainage. We haven't confirmed this against a published source yet. 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 Sisal Hemp actually grow on my specific land in Washington?
State-level zone + climate data is a sketch. A Growable Ground parcel report scores sisal hemp against your address's mapped 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 sisal hemp against your land's mapped soil, modelled sun, drainage, and frost data — not zone averages.
Three things about your lot that Washington sisal hemp 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 sisal hemp average
Explore More
Growing guides for sisal hemp
Explore Washington county by county
Washington carries 39 counties with their own USDA zone — a sample of the growing pages for sisal hemp there:
Where else sisal hemp grows
Sisal Hemp's zone band crosses state lines — these are the states closest to Washington in winter climate where it also has a page, plus the far ends of its range. Each one re-answers the question with that state's own record.
More to grow in Washington
Washington has a growing page for 1,033 plants — a rotating sample of the rest of the shelf.
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