Generally — Most Areas
purple prairie clover (zones 4-10) suits most of Montana (3a-6b) — zones 4-6 are in range, and the rest of the state is the exception.
Purple Prairie Clover in Montana — the short answer
Purple Prairie Clover in Montana: hardy in zones 4–10, full sun, against a state median of ~151 frost-free days.
- Plant zones
- 4-10
- Manual horticultural correction (source not retained); NC State Extension and Missouri Botanical Garden, with the remaining rows from other published sources or Growable Ground compilation
- Montana zones
- 3a-6b
- USDA PHZM 2023
- Frost window
- May 2 - May 13 – Sep 28 - Oct 7
- NOAA RCC ACIS 1991-2020, 28°F
- Shortest county season
- 59 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.
Montana spans zones 3a-6b, 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 purple prairie clover against your parcel's actual hardiness, soil, and sun.
We read public map data for this spot — soil, climate, flood, and parcel records. How we handle your address.
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Montana is not one climate
Montana’s winter-low ladder runs across 56 counties, from zone 3.5 in Daniels County to zone 6 in Sanders County. That is 25°F between the two counties’ average coldest night — the difference between purple prairie clover overwintering in the ground and coming under cover.
The middle half of 56 counties runs 4–5 zones, with a median of 4.5 zones — a 2.5-zone span end to end.
Measured across 56 Montana counties. USDA PHZM 2023, per county. 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 in Montana Fits Best
Purple Prairie Clover is rated for zones 4–10 — a cold floor USDA puts at -30 to -20°F. Against Montana’s 56 counties that band holds in 53 of them, and the line runs at Blaine County (zone 4a), the coldest county still inside it.
Inside zones 4–10
53 counties
- Carter County · zone 4a
- Chouteau County · zone 4a
- Dawson County · zone 4a
3 of 53 shown
Below the zone 4 floor
3 counties
- Daniels County · zone 3b
- Roosevelt County · zone 3b
- Sheridan County · zone 3b
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.
Even within Montana's zones 3a-6b, county microclimates differ enough to change what thrives. These counties carry the closest zone match for purple prairie clover (USDA PHZM 2023):
Zone Comparison
Purple Prairie Clover Needs
- USDA Zones: 4-10
- Frost-Free Days: 120+
- Sun: Full Sun
- Mature size: 2 ft tall
- Picking window: ~30 days of harvest
- Drought tolerance: Medium
Montana Has
- USDA Zones: 3a-6b
- Last Hard Freeze (28°F): May 2 - May 13
- First Hard Freeze (28°F): Sep 28 - Oct 7
- Annual Rainfall: 10-20 inches
- Common Soils: Sandy loam, Clay, Glacial till
Plant Zone Range (zones 4-10)
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 Purple Prairie Clover in Montana
The frost window
Across Montana, the last spring hard freeze (28°F) clears between May 2 and May 13, and the first fall hard freeze lands between Sep 28 and Oct 7 (NOAA Regional Climate Centers ACIS, 1991-2020). Counting from the latest last freeze to the earliest first freeze, that's a 138-day window you can count on — up to 158 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.
Winter standing
Montana runs as cold as USDA zone 3, and no sourced winter-hardiness floor is on record for purple prairie clover, so this page does not state whether it overwinters here — and gives no fall establishment date on the strength of a guess. Whether purple prairie clover is a permanent planting or a replant-every-spring crop for you turns on your own zone within Montana; check its hardiness range against that before treating it as long-lived ground.
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 purple prairie clover survives winter in part of Montana, not across all of it. Whether the season is long enough — and warm enough — is a different question.
Frost-free days
Purple Prairie Clover wants 120+ frost-free days; a typical Montana site sees ~151 (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
Purple Prairie Clover likes near-neutral soil (pH 6-8). That's the common-ground band across Montana's sandy loam and clay — a soil test confirms it for your site.
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. Montana soil profile from USDA NRCS SSURGO. Site-specific verification: a 30-minute soil test from your local Extension lab.
What Else to Consider for Purple Prairie Clover in Montana
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)
Low rainfall requires irrigation in most areas
Extreme winter cold (-40F possible)
What to actually do about these — and the constraints that apply to every Montana grower, not just purple prairie clover — is covered on the Montana growing guide.
Timing shifts within Montana
Purple Prairie Clover needs about 120 days of frost-free season to complete its cycle. 50 of Montana’s 56 counties give it that outright. The tightest that does is Jefferson County at 123 frost-free days — 3 to spare. Below that line you are transplanting or extending the season, not direct-sowing.
Across Montana’s 56 counties the frost-free season runs from 59 days in Deer Lodge County to 170 days in Petroleum County — a spread of 111 days, which is why a single statewide planting date misleads. The median Montana county sees 151 frost-free days, leaving purple prairie clover about 31 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"). Purple Prairie Clover's 120-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
Purple Prairie Clover draws native bees and butterflies (high value, Growable Ground Plant Database). Planting it near vegetable beds can lift fruit set on neighboring crops. Outdoors, purple prairie clover can only work that bloom inside Montana's frost window — roughly 151 days, opening after the last 28°F freeze (May 2 - May 13) and closing at the first (Sep 28 - Oct 7), per NOAA Regional Climate Centers ACIS, 1991-2020.
Montana Cooperative Extension
For Montana-specific cultivar recommendations, planting calendars, and pest pressure for purple prairie clover, the canonical source is Montana State University Extension. Their fact sheets carry the local trial data we can't generalize across 50 states.
Is Purple Prairie Clover native to Montana?
Yes — the USDA PLANTS Database (accessed 2026-07-01) documents Purple Prairie Clover as native to Montana. Planting it supports the pollinators and wildlife that evolved alongside it.
Native-range data: USDA PLANTS Database state-distribution records, accessed 2026-07-01.
Common Questions About Growing Purple Prairie Clover in Montana
When can I plant Purple Prairie Clover in Montana?
Montana's last spring hard freeze (28°F) clears between May 2 and May 13, and the first fall hard freeze lands between Sep 28 and Oct 7 (NOAA Regional Climate Centers ACIS, 1991-2020). No sourced winter-hardiness floor is on record for Purple Prairie Clover, so this page does not state whether it overwinters in Montana and publishes no fall establishment date for it — check its hardiness range against your own zone before treating it as a permanent planting.
What hardiness zone is Purple Prairie Clover grown in across Montana?
Montana spans USDA hardiness zones 3a-6b (USDA ARS PHZM 2023). Purple Prairie Clover 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 Montana site have?
A typical Montana site sees ~151 frost-free days per year (derived from NOAA Regional Climate Centers ACIS, 1991-2020). Purple Prairie Clover 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 Purple Prairie Clover native to Montana?
Yes — the USDA PLANTS Database (accessed 2026-07-01) documents Purple Prairie Clover as native to Montana. Planting it supports the pollinators and wildlife that evolved alongside it.
How should I amend the soil for Purple Prairie Clover in Montana?
Purple Prairie Clover prefers pH 6-8 (USDA PLANTS). 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 Purple Prairie Clover actually grow on my specific land in Montana?
State-level zone + climate data is a sketch. A Growable Ground parcel report scores purple prairie clover 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 purple prairie clover against your parcel's exact soil, sun, drainage, and frost data — not zone averages.
Three things about your lot that Montana purple prairie clover averages can't show:
We read public map data around Montana — soil, climate, flood, and parcel records. How we handle your address.
25+ data sources read at your address, not the Montana purple prairie clover average
Explore More
Growing guides for purple prairie clover
Explore Montana county by county
Montana carries 56 counties with their own USDA zone — a sample of the growing pages for purple prairie clover there:
Where else purple prairie clover grows
Purple Prairie Clover's zone band crosses state lines — these are the states closest to Montana 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 Montana
Montana has a growing page for 747 plants — a rotating sample of the rest of the shelf.
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