Mount Ayr, Indiana, sits in USDA hardiness zone 5b — a range where zone-matched perennials and frost-aware annual timing set what succeeds.
Growers here do well with cabbage, cranberry, lavender, and collard greens — with the usual caveat that any single yard's soil, sun, and drainage cast the deciding vote.
Even in Mount Ayr, no two yards are alike.
A low spot, a south-facing slope, or a stand of trees moves the frost date and sun across a single Mount Ayr lot. Enter your address and we'll score 1,086 plants against your land's actual soil, sun, and frost.
We read public map data around Mount Ayr — soil, climate, flood, and parcel records. How we handle your address.
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Mount Ayr — the short answer
Mount Ayr, Indiana: USDA zone 5b, about 202 days between hard freezes, across 112 acres of town.
- USDA zone
- 5b
- USDA PHZM 2023
- Last hard freeze (28°F)
- Apr 10
- NOAA 1991–2020 Climate Normals, 28°F — this town
- First hard freeze (28°F)
- Oct 29
- NOAA 1991–2020 Climate Normals, 28°F — this town
- Days between freezes
- ~202
- NOAA 1991–2020 Climate Normals, 28°F — this town
- Town area
- 112 acres
- US Census TIGER/Line 2025
Every figure names the dataset it came from. Hard-freeze dates are this town’s own 28°F normals: light frosts run a few weeks past them, and tender transplants usually wait 2–3 weeks after the last hard freeze.
Hardiness Zone Range
Zone 5b is Mount Ayr's average, not your lot's — a low corner or a tree line moves it. Against Mount Ayr's 202-day season, see what your own ground reads.
Soil varies lot by lot — soil types explained.
What this means for growing in Mount Ayr
Each reading below is measured for Mount Ayr itself — here is what it means for a garden here, and the move an experienced grower makes about it.
Season length
MeasuredMount Ayr runs about 202 days between hard freezes — a long growing season.
There is slack for succession plantings and slow-finishing crops: many vegetables can be sown twice, and the heat-lovers have time to ripen fully.
Plan a second sowing of quick crops after the first comes out, and use the fall window most gardeners let sit idle.
NOAA 1991–2020 Climate Normals
Winter hardiness
MeasuredMount Ayr sits in USDA hardiness zone 5b.
The zone sets which perennials, shrubs, and fruit trees live through an average winter here — a plant rated for a colder zone is a safe bet, one rated warmer needs winter protection or gets treated as an annual.
Match perennials and fruit to the zone before you buy, so nothing you plant is a gamble against the cold.
USDA PHZM 2023
The kind of country Mount Ayr is in
Mount Ayr sits in the Central Corn Belt Plains — EPA Level III, inside the wider Eastern Temperate Forests. That is read at Mount Ayr's own centroid rather than borrowed from Newton County.
What Grows in Mount Ayr
Every plant below cleared Mount Ayr's own zone 5b and its 202-day season. Each card opens that plant's Indiana profile. How we score.
Is it too late to plant in Mount Ayr?
Too late for some crops, right on time for others — a growing season is a sequence, not a deadline. Cool-season crops can go in from around Mar 13; tender transplants wait until two to three weeks after the last 28°F hard freeze, which lands near Apr 10 (NOAA 1991–2020 climate normals); and from midsummer, planting counts back from the first fall freeze around Oct 29 — long-season crops need about 90 days of runway, quick greens only 30. A long window like this one runs successions deep into fall — and even its last weeks take quick greens and garlic.
Documented around Mount Ayr
Survey cells within 31 miles of Mount Ayr checked for spotted lanternfly, none carrying a detection — a surveyed negative, not an absence of looking. Nearest documented record 48 miles off. What to watch for.
What's on the federal record near Mount Ayr
Closest first, within ~10 miles of Mount Ayr. Listing isn't leaking, and distance isn't exposure.
- 29N7W-20.1ANitrate · 2.8 mi
- 29N7W-31.1fNitrate · 2.9 mi
- WILSON BROTHERS FARM CENTER INCORPORATEDUnderground Storage Tanks · 3.1 mi
- NEWTON COUNTY LANDFILLToxics Release Inventory · 3.1 mi
- Trail Tree Truck StopUnderground Storage Tanks · 3.9 mi
- Grandmas Auto Truck PlazaUnderground Storage Tanks · 4.0 mi
- GRATNER INCORPORATEDUnderground Storage Tanks · 4.2 mi
- USGS WELL N36 NEAR FAIR OAKS, IN AKA 540025475135Nitrate · 4.2 mi
- Fair Oaks FarmUnderground Storage Tanks · 4.3 mi
- MCDONALDS RESTAURANTUnderground Storage Tanks · 4.4 mi
- Family Express 35Underground Storage Tanks · 4.4 mi
- IDEM PESTICIDE SURVEY WELL 454Nitrate · 4.6 mi
6 more sites are on the record inside the same radius. See them on the map
Measured from Mount Ayr's center, not your beds. Run your own address for what's upwind of you specifically.
Environmental Intelligence
The counts behind that headline — every source type on the record near Mount Ayr.
Total Sites
187
within ~10 miles of Mount Ayr
Risk Level
Elevated
Highest-severity
1 Superfund site (none NPL-listed)
Sources Checked
within ~10 miles of Mount Ayr
Severity Distribution
within ~10 miles of Mount Ayr
Highest-Severity Sites
A note from Gnorman
What an experienced grower watches for around here
In and around Mount Ayr, Nitrate runs higher than the national average — 80 sites within ~10 miles of Mount Ayr. Knowing it is half the work — and it's nothing a thoughtful grower can't plan for.
Nitrate: Nitrate contamination primarily comes from agricultural fertilizer runoff and failing septic systems.
Test well water for nitrate if you rely on a private well for irrigation (EPA standard: 10 mg/L).
Check your specific parcel in Mount Ayr
Get exact proximity distances to contamination sources for your specific parcel — plus soil, sun, drainage, and 1,086 plant recommendations.
25+ data sources read at your address, not the Mount Ayr average
Your land is one point inside Mount Ayr
Everything above resolves to Mount Ayr as a whole — one PHZM band and one 28°F frost record, read across 112 acres. Your parcel is one point inside that footprint. Slope, tree cover, a low spot that pools cold air, and what is in the soil are all resolved at the address, and none of them are visible at town scale. That is the honest boundary of this page, and the reason the next step is a reading of your own ground rather than a better local average.
Your Lot vs the Mount Ayr Average
Mount Ayr Average
- ●USDA Zones 5b, averaged across Mount Ayr
- ●One soil character for all of Mount Ayr
- ●Frost dates read at Mount Ayr's scale: Apr 10 to Oct 29
YOUR Parcel
- ✓Your exact zone, not Mount Ayr's 5b
- ✓Your SSURGO soil type & pH
- ✓Your sun exposure, cast in 3D
See MY Growing Report
Read your specific parcel in Mount Ayr
Pull a site-specific report for your exact address in Mount Ayr, Indiana — soil, sun, drainage, frost risk, and scored plant recommendations.
Three things about your lot that Mount Ayr averages can't show:
We read public map data around Mount Ayr — soil, climate, flood, and parcel records. How we handle your address.
25+ data sources read at your address, not the Mount Ayr average
How we know this about Mount Ayr
The datasets: hardiness from the USDA ARS Plant Hardiness Zone Map 2023, read at this town’s own centroid; hard-freeze dates from NOAA 1991–2020 28°F normals at Mount Ayr’s own record; boundaries and acreage from US Census TIGER/Line 2025; the contamination records from the federal sources named in their beats above. Soil is not read at town grain anywhere on this page — there is no town-resolution survey in our data, which is why you will find no soil grid here rather than a statewide one wearing a local label. The resolution ledger below names every figure this page inherited.
Common questions about Mount Ayr
When does frost risk typically end in Mount Ayr?
The last hard freeze (28°F) in Mount Ayr typically lands around Apr 10, per NOAA 1991–2020 climate normals — earlier than the light-frost dates most charts quote. That marks the hard freeze, not the last light frost — lighter frosts keep biting past it, which is why tender transplants here wait until about May 1.
When is the first frost in Mount Ayr?
The first hard freeze (28°F) in Mount Ayr typically arrives around Oct 29, per NOAA 1991–2020 climate normals — the point tender summer crops finish. Lighter frosts run ahead of it, near Oct 15, so the watching starts about Sep 29 — about 202 days after the spring freeze cleared.
How long is the growing season in Mount Ayr?
Measured between 28°F hard freezes, Mount Ayr sees about 202 frost-free days — roughly Apr 10 through Oct 29, per NOAA 1991–2020 climate normals. Tender crops work a shorter one: nearer May 1 to Oct 15, about 167 days.
Is the soil safe to grow vegetables in Mount Ayr?
The federal record around Mount Ayr is a meaningful one — 187 documented sites, mostly Nitrate entries (80), the nearest Nitrate record about 2.8 miles out — so a soil test before new food beds is a sensible precaution here, not a reason to hold back from growing. Remember that proximity to a documented site is information, not a diagnosis of any one yard; the contamination map shows exactly what sits where.
How do I protect my plants from frost in Mount Ayr?
From about Sep 29 the job here turns from planting to protecting — the last start even a 30-day crop can finish. As the season closes around the first 28°F hard freeze near Oct 29 (NOAA 1991–2020 climate normals), three moves buy time: row cover or an old sheet over tender plants on still, clear nights; water the soil the afternoon before a freeze, so it holds warmth overnight; and harvest tomatoes, peppers and basil before Oct 29. Hardy greens and roots shrug off light frost and sweeten after it — leave them in.
Everything above is measured at Mount Ayr's scale — its 5b band and its 202-day season. Your yard writes its own version of Mount Ayr's numbers: we read soil, sun, drainage and frost at your exact address. Try it for 14 days — no card required.
What this page reads at Mount Ayr’s own scale
7 of the readings below were taken at Mount Ayr's own scale — its own ~202-day season between 28°F freezes, the 112 acres it covers and 187 documented sites around it; 4 are borrowed from a wider read, named and linked below.
Measured here
- Mount Ayr's own USDA hardiness band, zones 5bUSDA PHZM 2023
- Mount Ayr's own 28°F hard-freeze dates, about Apr 10 and Oct 29 and the ~202-day span between themNOAA 1991–2020 Climate Normals
- 187 documented contamination sites on the federal record near Mount Ayr, the closest Nitrate record about 2.8 miles out from the town centreFederal environmental registers
- Mount Ayr's boundary and the 112 acres inside itUS Census TIGER/Line 2025
- Which of 1,086 plants clear zones 5b and a ~202-day seasonGrowable Ground crop-matching engine
- The ecoregion at Mount Ayr's own centroid, the Central Corn Belt PlainsUS EPA Level III Ecoregions
- Lanternfly survey cells around Mount Ayr checked, none carrying a detectionlydemapr (De Bona & Helmus), 10 km survey lattice
Inherited from a wider read
- Soil character — no town-scale survey exists, so Mount Ayr's 112 acres read through its county's SSURGO summaryfrom Newton County
- Growing-degree days and winter chill — measured county-wide only, so the county page carries themfrom Newton County
- The growing challenges every Indiana grower plans around — written at state scale, so they stay on the state guidefrom Indiana
- Butterfly and beetle records, and the farmland pesticide estimate — all published county-widefrom Newton County
What this page can’t tell you
- The soil pH, drainage, sun hours, and frost pockets on any one lot among Mount Ayr's 112 acreswhy one lot differs from the next →
- Which side of Mount Ayr you're on — a low spot frosts first and a south wall warms early, and one normal is being asked to speak for all 112 acresreading your own microclimate →
- How close that record sits to YOUR lot — the closest Nitrate record about 2.8 miles out, measured from the town centrehow we read the record →
- Where cold air settles, which slopes face the sun, and which way the wind runs on your own ground — measured at your address, and averaged away by any Mount Ayr-wide figureread your own land →
More in Indiana
Wider growing context
What grows across IndianaMount Ayr sits outside our named growing regions, so Indiana as a whole is its closest context here.
Nearby growing guides