Conditional — Some Areas
autumn fern (zones 6-8) reaches only part of Iowa (4b-6a): zone 6 are in range, so where you are in the state decides it.
Autumn Fern in Iowa — the short answer
Autumn Fern in Iowa: hardy in zones 6–8, part sun, against a state median of ~189 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
- Iowa zones
- 4b-6a
- USDA PHZM 2023
- Frost window
- Apr 10 - Apr 17 – Oct 18 - Oct 23
- NOAA RCC ACIS 1991-2020, 28°F
- Shortest county season
- 168 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.
Iowa spans zones 4b-6a, 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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Iowa is not one climate
A single Iowa answer averages 99 counties whose growing seasons are 48 days apart — from 168 frost-free days in Howard County to 216 in Lee County. Which end of that your land sits nearer changes what autumn fern can finish before the first hard freeze.
The middle half of 99 counties runs 183–197 days, with a median of 189 days — a 48-day span end to end.
Measured across 99 Iowa 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 Iowa Fits Best
Autumn Fern is rated for zones 6–8 — a cold floor USDA puts at -10 to 0°F. Against Iowa’s 99 counties that band holds in 2 of them, and the line runs at Des Moines County (zone 6a), the coldest county still inside it.
Inside zones 6–8
2 counties
0 of 2 shown
Below the zone 6 floor
97 counties
- Clayton County · zone 4b
- Howard County · zone 4b
- Winneshiek County · zone 4b
3 of 97 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 Iowa's zones 4b-6a, 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
Iowa Has
- USDA Zones: 4b-6a
- Last Hard Freeze (28°F): Apr 10 - Apr 17
- First Hard Freeze (28°F): Oct 18 - Oct 23
- Annual Rainfall: 26-36 inches
- Common Soils: Prairie loess, Silt loam, Clay loam
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 Iowa
The frost window
Across Iowa, the last spring hard freeze (28°F) clears between Apr 10 and Apr 17, and the first fall hard freeze lands between Oct 18 and Oct 23 (NOAA Regional Climate Centers ACIS, 1991-2020). Counting from the latest last freeze to the earliest first freeze, that's a 184-day window you can count on — up to 196 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 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.
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. Iowa 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 Iowa
Zone compatibility tells you about winter cold survival — but Iowa growers also need to think about:
Cold winters reaching -20F or below
Variable spring weather delays planting
Wind exposure on open prairies desiccates plants
What to actually do about these — and the constraints that apply to every Iowa grower, not just autumn fern — is covered on the Iowa growing guide.
Where in Iowa Autumn Fern Is Zone-Hardy
Autumn Fern is rated for USDA zones 6–8. 2 of Iowa’s 99 counties fall inside that band. The coldest that does is Des Moines County at zone 6a. 97 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 Iowa decides this one.
Across those 99 counties Iowa’s winter-low ladder runs from zone 4b in Clayton County to zone 6a in Lee County — 1.5 USDA zones of spread, which is 15°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. Howard County holds its last hard freeze (28°F) until about Apr 24, while Lee County is clear by Apr 1 — 23 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.
Iowa Cooperative Extension
For Iowa-specific cultivar recommendations, planting calendars, and pest pressure for autumn fern, the canonical source is Iowa State University Extension and Outreach. Their fact sheets carry the local trial data we can't generalize across 50 states.
Common Questions About Growing Autumn Fern in Iowa
When can I plant Autumn Fern in Iowa?
Iowa's last spring hard freeze (28°F) clears between Apr 10 and Apr 17, and the first fall hard freeze lands between Oct 18 and Oct 23 (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 Iowa?
Iowa spans USDA hardiness zones 4b-6a (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 Iowa site have?
A typical Iowa site sees ~189 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.
Will Autumn Fern actually grow on my specific land in Iowa?
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 Iowa
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 Iowa autumn fern averages can't show:
We read public map data around Iowa — soil, climate, flood, and parcel records. How we handle your address.
25+ data sources read at your address, not the Iowa autumn fern average
Explore More
Growing guides for autumn fern
Explore Iowa county by county
Iowa carries 99 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 Iowa 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 Iowa
Iowa has a growing page for 806 plants — a rotating sample of the rest of the shelf.
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