Conditional — Some Areas
spear grass (zones 9-13) has limited zone overlap with Oregon (4b-9b). Only zones 9-9 in the state are suitable.
Your yard isn't the whole zone.
Oregon spans zones 4b-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 spear grass against your land's actual soil, sun, and frost.
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Zone Comparison
Spear Grass Needs
- USDA Zones: 9-13
- Soil pH: 4.5 - 8.5
- Sun: Full Sun
- Drainage: well (dry spells)
- Frost-Free Days: 120+
Oregon Has
- USDA Zones: 4b-9b
- Last Frost: Mar 1 - Jun 15
- First Frost: Sep 1 - Nov 15
- Annual Rainfall: 8-90 inches
- Common Soils: Volcanic, Silt loam (Willamette), Sandy loam
Plant Zone Range (zones 9-13)
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 Spear Grass in Oregon
The frost window
Across Oregon, the last spring frost clears between Mar 1 and Jun 15, and the first fall frost lands between Sep 1 and Nov 15 (NOAA Climate Normals 1991-2020). Counting from the latest last frost to the earliest first frost, that's a 78-day window you can count on — up to 259 days on a mild site in a kind year.
Frost tenderness
Spear Grass is frost-tender — its listed minimum temperature is 68°F (USDA PLANTS Database) — so set plants out after the last frost has cleared your local site, not the state's earliest date.
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
Spear Grass wants 120+ frost-free days; a typical Oregon site sees ~170 (NOAA Climate Normals). That leaves a workable window — start indoors to bank time.
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
Spear Grass likes near-neutral soil (pH 4.5-8.5). That's the common-ground band across Oregon's volcanic and silt loam (willamette) — a soil test confirms it for your site. Drainage matters: this plant wants well (dry spells). If your Oregon site is heavier clay or sits in a low spot, raised beds or amendment with compost solve it.
Plant pH and drainage requirements from USDA PLANTS Database. Oregon soil profile from USDA NRCS SSURGO. Site-specific verification: a 30-minute soil test from your local Extension lab.
Spear Grass in Oregon — Quick Answer
- Verdict: Conditional — Some Areas
- Plant Zones: 9-13 (USDA PLANTS Database)
- State Zones: 4b-9b (USDA ARS PHZM 2023)
- Growing Season: Mar 1 - Jun 15 to Sep 1 - Nov 15 (NOAA Climate Normals)
What Else to Consider
Zone compatibility tells you about winter cold survival — but Oregon growers also need to think about:
West side: excessive rain and overcast skies reduce sun for warm-season crops
Map your sun honestly — a south-facing bed against a light wall recovers a surprising amount of the light the clouds take.
East side: arid conditions (8-15 inches rainfall) require irrigation
East of the Cascades, drip irrigation is infrastructure, not an accessory — plan it before the first planting.
Slug pressure is extreme in western Oregon
Evening patrols, iron-phosphate baits, and dry mulch edges knock slugs back — your extension guide covers the full toolkit.
Mountain areas have very short seasons (60-90 frost-free days)
At 60-90 frost-free days, season extension is the difference between a garden and a gamble — a high tunnel changes the math.
Oregon Cooperative Extension
For Oregon-specific cultivar recommendations, planting calendars, and pest pressure for spear grass, the canonical source is OSU Extension Service. Their fact sheets carry the local trial data we can't generalize across 50 states.
Is Spear Grass native to Oregon?
Spear Grass is native to parts of the Lower 48, but the USDA PLANTS Database (accessed 2026-07-01) does not document a native range in Oregon. It can still earn a place in a Oregon garden — the zone comparison above tells you whether it will thrive.
Looking for plants that belong here? The Oregon 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 Spear Grass in Oregon
When can I plant Spear Grass in Oregon?
Oregon's last spring frost clears between Mar 1 and Jun 15, and the first fall frost lands between Sep 1 and Nov 15 (NOAA Climate Normals 1991-2020). Spear Grass is frost-tender — its listed minimum temperature is 68°F (USDA PLANTS Database) — so wait until the last frost has cleared your specific site before planting out.
What hardiness zone is Spear Grass grown in across Oregon?
Oregon spans USDA hardiness zones 4b-9b (USDA ARS PHZM 2023). Spear Grass carries a range of zones 9-13, so the overlap zones are where outdoor growing is most reliable.
How many frost-free days does a typical Oregon site have?
A typical Oregon site sees ~170 frost-free days per year (derived from NOAA Climate Normals 1991-2020). Spear Grass needs 120+ frost-free days, so check whether your local microclimate runs above or below the state average before settling on a planting date.
Is Spear Grass native to Oregon?
Spear Grass is native to parts of the Lower 48, but the USDA PLANTS Database (accessed 2026-07-01) does not document a native range in Oregon. It can still earn a place in a Oregon garden — the zone comparison above tells you whether it will thrive.
How should I amend the soil for Spear Grass in Oregon?
Spear Grass prefers pH 4.5-8.5 and well (dry spells) drainage (USDA PLANTS Database). That sits in the common-ground band across Oregon soils — a 30-minute soil test from a local Extension lab confirms it for your specific site.
Will Spear Grass actually grow on my specific land in Oregon?
State-level zone + climate data is a sketch. A Growable Ground parcel report scores spear grass 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 Oregon
State-level data is a sketch. Your Growable Ground report scores spear grass 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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