Yes — Strong Match
osteospermum (zones 2-11) covers every zone Montana contains (3a-6b), so hardiness is not what limits it anywhere in the state.
Osteospermum in Montana — the short answer
Osteospermum in Montana: hardy in zones 2–11, full sun, against a state median of ~151 frost-free days.
- Plant zones
- 2-11
- 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
- Days to maturity
- 60 days
- Growable Ground Plant Database
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.
Osteospermum is grown as an annual, so your winter zone isn't the deciding factor — your frost-free window is. A typical Montana site runs ~151 frost-free days, but that is a state median, not your yard: slope, trees, and low spots move the last-frost date across a single parcel. Enter your address and we'll score osteospermum against your land's actual frost dates, sun, and soil.
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Montana is not one climate
A single Montana answer averages 56 counties whose growing seasons are 111 days apart — from 59 frost-free days in Deer Lodge County to 170 in Petroleum County. Which end of that your land sits nearer changes what osteospermum can finish before the first hard freeze.
The middle half of 56 counties runs 137–158 days, with a median of 150 days — a 111-day span end to end.
Measured across 56 Montana 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 in Montana Fits Best
Even within Montana's zones 3a-6b, county microclimates differ enough to change what thrives. These counties carry the closest zone match for osteospermum (USDA PHZM 2023):
Zone Comparison
Osteospermum Needs
- USDA Zones: 2-11
- Frost-Free Days: 60+
- Sun: Full Sun
- Mature size: 2 ft tall
- Picking window: ~90 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 2-11)
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 Osteospermum 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.
Frost tenderness
Osteospermum is frost-tender — FAO ECOCROP puts its killing temperature at 32°F — so set plants out two to three weeks PAST your local last hard freeze, not on it and not on the state's earliest date. The 28°F marker above is when killing freezes stop, not when light frost does. 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.
When to start the seed
Those dates are when osteospermum goes out, not when it starts. It is sown under cover about 8 weeks ahead, so counting back from Montana's late-side last freeze of May 13 is what fixes your sowing date — and a yard that clears frost earlier than the state's late date starts earlier still.
Days to maturity vs. the window
At 60 days to maturity (Growable Ground Plant Database), counting from the last hard freeze it ripens with 78 days to spare even in Montana's tightest freeze scenario — room for a later start or a second sowing.
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 osteospermum survives winter here. Whether the season is long enough — and warm enough — is a different question.
Frost-free days
Osteospermum wants 60+ frost-free days; a typical Montana site sees ~151 (NOAA Regional Climate Centers ACIS, 1991-2020). That leaves comfortable headroom for succession planting.
Growing degree days
Osteospermum needs ~1100 GDD (base 50°F) to ripen. The state median runs ~1769 GDD (from PRISM 1991-2020 climate normals), so Montana's typical season clears that easily.
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
Osteospermum likes near-neutral soil (pH 5.5-7.5). That's the common-ground band across Montana's sandy loam and clay — a soil test confirms it for your site. It will grow across that whole span, but it does best between pH 6 and 6.5 — worth knowing before you decide whether a Montana soil test result is a problem or just a number. 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 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 Osteospermum 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 osteospermum — is covered on the Montana growing guide.
Timing shifts within Montana
Osteospermum needs about 60 days of frost-free season to complete its cycle. 55 of Montana’s 56 counties give it that outright. The tightest that does is Gallatin County at 114 frost-free days — 54 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 osteospermum about 91 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"). Osteospermum's 60-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
Osteospermum draws honeybees, native bees, and butterflies (moderate value, Growable Ground Plant Database). Planting it near vegetable beds can lift fruit set on neighboring crops. Outdoors, osteospermum 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 osteospermum, the canonical source is Montana State University Extension. Their fact sheets carry the local trial data we can't generalize across 50 states.
Is Osteospermum native to Montana?
No — the USDA PLANTS Database lists Osteospermum as introduced rather than native in the Lower 48, so it is not part of Montana's native flora. It grows here as a garden plant; pairing it with a few Montana natives keeps local pollinators fed too.
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 Osteospermum in Montana
When can I plant Osteospermum 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). Osteospermum is frost-tender — its killing temperature is 32°F (FAO ECOCROP — the point where cold damages growing tissue, not a winter-survival floor) — so wait two to three weeks past your site's last hard freeze, when light frost has also stopped, before planting out.
Can Osteospermum mature before first frost in Montana?
Yes — Osteospermum matures in 60 days (Growable Ground Plant Database), and Montana's dependable hard-freeze-free window runs 138 days (NOAA Regional Climate Centers ACIS, 1991-2020), leaving 78 days of margin. Plant once the last hard freeze has passed — two to three weeks later for anything tender — and it ripens ahead of the first fall freeze.
What hardiness zone is Osteospermum grown in across Montana?
Montana spans USDA hardiness zones 3a-6b (USDA ARS PHZM 2023). Osteospermum 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 ~151 frost-free days per year (derived from NOAA Regional Climate Centers ACIS, 1991-2020). Osteospermum needs 60+ frost-free days, so check whether your local microclimate runs above or below the state average before settling on a planting date.
Is Osteospermum native to Montana?
No — the USDA PLANTS Database lists Osteospermum as introduced rather than native in the Lower 48, so it is not part of Montana's native flora. It grows here as a garden plant; pairing it with a few Montana natives keeps local pollinators fed too.
How should I amend the soil for Osteospermum in Montana?
Osteospermum prefers pH 5.5-7.5 and well (dry spells) drainage (Growable Ground Plant 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 Osteospermum actually grow on my specific land in Montana?
State-level zone + climate data is a sketch. A Growable Ground parcel report scores osteospermum 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 osteospermum against your parcel's exact soil, sun, drainage, and frost data — not zone averages.
Three things about your lot that Montana osteospermum 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 osteospermum average
Explore More
Growing guides for osteospermum
Explore Montana county by county
Montana carries 56 counties with their own USDA zone — a sample of the growing pages for osteospermum there:
Where else osteospermum grows
Osteospermum'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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