Conditional — Some Areas
phacelia (zones 2-11) has limited zone overlap with Montana (3a-5b). Only zones 3-5 in the state are suitable.
Your yard isn't the whole zone.
Phacelia is grown as an annual, so your winter zone isn't the deciding factor — your frost-free window is, and slope, trees, and low spots move the last-frost date across a single yard. Enter your address and we'll score phacelia against your parcel's actual frost dates, sun, and soil.
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Zone Comparison
Phacelia Needs
- USDA Zones: 2-11
- Soil pH: 6.4 - 8.6
- Sun: Full Sun
- Drainage: well (dry spells)
- Frost-Free Days: 100+
Montana Has
- USDA Zones: 3a-5b
- Last Frost: May 1 - Jun 15
- First Frost: Aug 25 - Oct 1
- Annual Rainfall: 10-20 inches
- Common Soils: Sandy loam, Clay, Glacial till
Plant Zone Range (zones 2-11)
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 Phacelia in Montana
The frost window
Across Montana, the last spring frost clears between May 1 and Jun 15, and the first fall frost lands between Aug 25 and Oct 1 (NOAA Climate Normals 1991-2020). Counting from the latest last frost to the earliest first frost, that's a 71-day window you can count on — up to 153 days on a mild site in a kind year.
Frost tenderness
Phacelia is frost-tender — its listed minimum temperature is 52°F (USDA PLANTS Database) — so set plants out after the last frost has cleared your local site, not the state's earliest date.
Days to maturity vs. the window
At 45 days to maturity (USDA PLANTS Database), one crop fits Montana's 71-day dependable window with 26 days of margin — plant at the front of the window to keep that cushion.
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
Phacelia wants 100+ frost-free days; a typical Montana site sees ~130 (NOAA Climate Normals). That leaves a workable window — start indoors to bank time.
Growing degree days
Phacelia needs ~1000 GDD (base 50°F) to ripen. The state median runs ~2250 GDD (USDA NRCS county aggregates), so Montana's typical season clears that easily.
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
Phacelia likes near-neutral soil (pH 6.4-8.6). That's the common-ground band across Montana's sandy loam and clay — a soil test confirms it for your site. Drainage matters: this plant wants well (dry spells). If your Montana 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. Montana soil profile from USDA NRCS SSURGO. Site-specific verification: a 30-minute soil test from your local Extension lab.
Phacelia in Montana — Quick Answer
- Verdict: Conditional — Some Areas
- Plant Zones: 2-11 (USDA PLANTS Database)
- State Zones: 3a-5b (USDA ARS PHZM 2023)
- Growing Season: May 1 - Jun 15 to Aug 25 - Oct 1 (NOAA Climate Normals)
- Days to Maturity: 45 days
What Else to Consider
Zone compatibility tells you about winter cold survival — but Montana growers also need to think about:
Very short growing season (60-100 frost-free days)
At 60-100 frost-free days, a high tunnel or cold frame isn't a luxury — it's the difference-maker Montana growers rely on.
Low rainfall requires irrigation in most areas
Drip irrigation plus mulch stretches scarce water a long way — plan the system before the first seed.
Extreme winter cold (-40F possible)
Choose perennials rated for the cold you actually get — a -40°F winter audits every optimistic zone push.
Pollinator + Wildlife Value
Phacelia draws pollinators (high value, USDA PLANTS Database). Planting it near vegetable beds can lift fruit set on neighboring crops.
Montana Cooperative Extension
For Montana-specific cultivar recommendations, planting calendars, and pest pressure for phacelia, the canonical source is Montana State University Extension. Their fact sheets carry the local trial data we can't generalize across 50 states.
Is Phacelia native to Montana?
Phacelia is native to parts of the Lower 48, but the USDA PLANTS Database (accessed 2026-07-01) does not document a native range in Montana. It can still earn a place in a Montana garden — the zone comparison above tells you whether it will thrive.
Looking for plants that belong here? The Montana 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 Phacelia in Montana
When can I plant Phacelia in Montana?
Montana's last spring frost clears between May 1 and Jun 15, and the first fall frost lands between Aug 25 and Oct 1 (NOAA Climate Normals 1991-2020). Phacelia is frost-tender — its listed minimum temperature is 52°F (USDA PLANTS Database) — so wait until the last frost has cleared your specific site before planting out.
Can Phacelia mature before first frost in Montana?
Yes — Phacelia matures in 45 days (USDA PLANTS Database), and Montana's dependable frost-free window runs 71 days (NOAA Climate Normals 1991-2020), leaving 26 days of margin. Plant just after last frost and it ripens ahead of the first fall frost.
What hardiness zone is Phacelia grown in across Montana?
Montana spans USDA hardiness zones 3a-5b (USDA ARS PHZM 2023). Phacelia carries a range of zones 2-11, so the overlap zones are where outdoor growing is most reliable.
How many frost-free days does a typical Montana site have?
A typical Montana site sees ~130 frost-free days per year (derived from NOAA Climate Normals 1991-2020). Phacelia needs 100+ frost-free days, so check whether your local microclimate runs above or below the state average before settling on a planting date.
Is Phacelia native to Montana?
Phacelia is native to parts of the Lower 48, but the USDA PLANTS Database (accessed 2026-07-01) does not document a native range in Montana. It can still earn a place in a Montana garden — the zone comparison above tells you whether it will thrive.
How should I amend the soil for Phacelia in Montana?
Phacelia prefers pH 6.4-8.6 and well (dry spells) drainage (USDA PLANTS Database). That sits in the common-ground band across Montana soils — a 30-minute soil test from a local Extension lab confirms it for your specific site.
Will Phacelia actually grow on my specific land in Montana?
State-level zone + climate data is a sketch. A Growable Ground parcel report scores phacelia 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 Montana
State-level data is a sketch. Your Growable Ground report scores phacelia 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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