Conditional — Some Areas
autumn fern (zones 6-8) reaches only part of Montana (3a-6b): zone 6 are in range, so where you are in the state decides it.
One zone short — what would close it
Autumn Fern is hardy to zone 6, and the warmest ground in Montana is zone 5 — 1 zone short. Planted in open ground it will not survive a Montana winter. To grow it here, grow autumn fern in a hoop house or unheated greenhouse — its modeled 1.5-zone lift covers this gap.
A hoop house or unheated greenhouse is the lift this needs. How a greenhouse changes what you can grow →
Zone math from 6-8 (plant) against 3-5 (Montana). Lift modeled by crop_engine.GREENHOUSE_ZONE_MODIFIER_BY_SUBTYPE['hoop_house'] (+1.5 zones) via api/fast_sections.py Unlock Engine v2.
Autumn Fern in Montana — the short answer
Autumn Fern in Montana: hardy in zones 6–8, part sun, against a state median of ~151 frost-free days.
- Plant zones
- 6-8
- 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 has its own microclimate — slope, trees, and low spots shift frost and sun across a single parcel. Enter your address and we'll score autumn fern 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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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 autumn fern 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
Autumn Fern is rated for zones 6–8 — a cold floor USDA puts at -10 to 0°F. Against Montana’s 56 counties that band holds in 5 of them, and the line runs at Lake County (zone 6a), the coldest county still inside it.
Below the zone 6 floor
51 counties
- Daniels County · zone 3b
- Roosevelt County · zone 3b
- Sheridan County · zone 3b
3 of 51 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.
Even within Montana's zones 3a-6b, county microclimates differ enough to change what thrives. These counties carry the closest zone match for autumn fern (USDA PHZM 2023):
Zone Comparison
Autumn Fern Needs
- USDA Zones: 6-8
- Sun: Part Sun
- Mature size: 2 ft tall
- Drought tolerance: Low
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 6-8)
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 Autumn Fern 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.
Timing tuned to sub-state frost dates — Deer Lodge County, not the statewide average.
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.
Soil + Drainage Fit
Drainage requirement: poorly (saturated >50% of year). A soil-survey lookup (NRCS SSURGO) flags whether your specific site matches.
Your land, not the state average
Montana's soils run mostly loam, but SSURGO maps the series, texture, and drainage under your exact parcel. What matters for autumn fern is the horizon its roots actually work, not the surface. That map unit, not the state average, decides how autumn fern performs.
Check your parcel → Source: USDA NRCS SSURGO.
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 Autumn Fern 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 autumn fern — is covered on the Montana growing guide.
Timing shifts within Montana
Montana isn't one climate. In Deer Lodge County, the last hard freeze (28°F) holds until about Jun 21 — roughly 47 days later than the recorded state median — so plant autumn fern to your county's window, not the statewide date.
County last-freeze dates: NOAA Regional Climate Centers ACIS (1991-2020), county 28°F freeze (earlier than the folk 32°F "last frost"). A parcel report resolves your address's own frost dates.
Where in Montana Autumn Fern Is Zone-Hardy
Autumn Fern is rated for USDA zones 6–8. 5 of Montana’s 56 counties fall inside that band. The coldest that does is Lake County at zone 6a. 51 counties sit below the plant’s zone 6 floor, where an unprotected plant is relying on snow cover and a mild year. Where you are in Montana decides this one.
Across those 56 counties Montana’s winter-low ladder runs from zone 3b in Daniels County to zone 6a in Sanders County — 2.5 USDA zones of spread, which is 25°F between the two counties’ average coldest night of the year. That is why a statewide hardiness answer is where you start and not where you finish.
The planting window moves with it. Deer Lodge County holds its last hard freeze (28°F) until about Jun 21, while Petroleum County is clear by Apr 25 — 57 days apart. Set autumn fern out on your county’s date, not the state’s.
County hardiness zones: USDA Plant Hardiness Zone Map (PHZM) 2023, per county. County last-freeze dates: NOAA Regional Climate Centers ACIS (1991-2020), county 28°F killing freeze — earlier than the folk 32°F "last frost". Autumn Fern’s zone 6–8 band: USDA PLANTS / Growable Ground plant database. A parcel report resolves your address’s own zone and frost dates rather than its county’s.
Recommended Autumn Fern Varieties for Montana
Montana publishes no state variety trial for autumn fern, so we won't invent a "best for Montana" list. Choose types rated to your USDA hardiness zone (3a-6b), and confirm winter survival and drainage against your own parcel.
Montana Cooperative Extension
For Montana-specific cultivar recommendations, planting calendars, and pest pressure for autumn fern, the canonical source is Montana State University Extension. Their fact sheets carry the local trial data we can't generalize across 50 states.
Common Questions About Growing Autumn Fern in Montana
When can I plant Autumn Fern 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). Time outdoor planting to after the last hard freeze for your specific site — a further two to three weeks for anything tender — and count back from those dates for transplant scheduling.
What hardiness zone is Autumn Fern grown in across Montana?
Montana spans USDA hardiness zones 3a-6b (USDA ARS PHZM 2023). Autumn Fern carries a range of zones 6-8, 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). Autumn Fern should be matched against that window, so check whether your local microclimate runs above or below the state average before settling on a planting date. In cooler counties like Deer Lodge, the freeze-free season runs shorter than the state average, so verify your own county's window.
Will Autumn Fern actually grow on my specific land in Montana?
State-level zone + climate data is a sketch. A Growable Ground parcel report scores autumn fern 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 autumn fern against your parcel's exact soil, sun, drainage, and frost data — not zone averages.
Three things about your lot that Montana autumn fern 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 autumn fern average
Explore More
Growing guides for autumn fern
Explore Montana county by county
Montana carries 56 counties with their own USDA zone — a sample of the growing pages for autumn fern there:
Where else autumn fern grows
Autumn Fern'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.
Analysis by the Growable Ground research team, grounded in USDA PLANTS, USDA NRCS SSURGO, NOAA Climate Normals (1991-2020), and named Cooperative Extension sources. How we know →
Cite this dataset
Kirchick, M. (2026). Growable Ground Plant Database [Data set]. Zenodo. https://doi.org/10.5281/zenodo.21435643
Licensed CC BY-NC 4.0. DOI 10.5281/zenodo.21435643
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