Mount Union, Iowa, sits in USDA hardiness zone 5b — a zone band wide enough that plant choice, not possibility, is the interesting question.
Crops well matched to these conditions include cabbage, blueberry, lavender, and collard greens — though what thrives on any one site still turns on its specific soil, sun, and drainage.
Even in Mount Union, 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 Union 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 Union — soil, climate, flood, and parcel records. How we handle your address.
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Mount Union — the short answer
Mount Union, Iowa: USDA zone 5b, about 205 days between hard freezes, across 108 acres of town.
- USDA zone
- 5b
- USDA PHZM 2023
- Last hard freeze (28°F)
- Apr 7
- 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
- ~205
- NOAA 1991–2020 Climate Normals, 28°F — this town
- Town area
- 108 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 Union's average, not your lot's — a low corner or a tree line moves it. Against Mount Union's 205-day season, see what your own ground reads.
Soil varies lot by lot — soil types explained.
What this means for growing in Mount Union
Each reading below is measured for Mount Union itself — here is what it means for a garden here, and the move an experienced grower makes about it.
Season length
MeasuredMount Union runs about 205 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 Union 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 Union is in
Mount Union sits in the Western Corn Belt Plains — EPA Level III, inside the wider Great Plains. That is read at Mount Union's own centroid rather than borrowed from Henry County.
What Grows in Mount Union
Every plant below cleared Mount Union's own zone 5b and its 205-day season. Each card opens that plant's Iowa profile. How we score.
Is it too late to plant in Mount Union?
Usually not — gardeners here simply switch what goes in the ground as the season moves. Cool-season crops can go in from around Mar 10; tender transplants wait until two to three weeks after the last 28°F hard freeze, which lands near Apr 7 (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. With a season this long, “too late” mostly means “switch crops” — second sowings and a full fall garden are the norm, with garlic closing the year.
What's on the federal record near Mount Union
Closest first, within ~10 miles of Mount Union. Listing isn't leaking, and distance isn't exposure.
- MOUNT UNION CO-OP ELEVATOR INCUnderground Storage Tanks · 550 ft
- WILKERSON 66Underground Storage Tanks · 900 ft
- 072N05W11ADD 03113 1947Nitrate · 0.5 mi
- HAZEN SUPPLY CORPUnderground Storage Tanks · 1.4 mi
- 073N04W30CDD 07974 1956Nitrate · 2.5 mi
- 072N04W05DCCC 07848 1956Nitrate · 2.6 mi
- KASER CORPORATIONUnderground Storage Tanks · 4.3 mi
- 072N05W17CCBB 11049 1959Nitrate · 4.3 mi
- 072N05W34ABB 14083 1962Nitrate · 4.3 mi
- 072N04W30DDDD 07830 1956Nitrate · 4.5 mi
- WINFIELD EQUIPMENT COUnderground Storage Tanks · 5.1 mi
- 073N04W17BCB 10302 1956Nitrate · 5.1 mi
6 more sites are on the record inside the same radius. See them on the map
Measured from Mount Union'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 Union.
Total Sites
160
within ~10 miles of Mount Union
Risk Level
Moderate
Highest-severity
5 Toxics Release Inventory facilities
Sources Checked
within ~10 miles of Mount Union
Severity Distribution
within ~10 miles of Mount Union
Highest-Severity Sites
A note from Gnorman
What an experienced grower watches for around here
In and around Mount Union, Nitrate runs higher than the national average — 84 sites within ~10 miles of Mount Union. That's not a problem with your land — it's information about it.
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 Union
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 Union average
Your land is one point inside Mount Union
Everything above resolves to Mount Union as a whole — one PHZM band and one 28°F frost record, read across 108 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 Union Average
Mount Union Average
- ●USDA Zones 5b, averaged across Mount Union
- ●One soil character for all of Mount Union
- ●Frost dates read at Mount Union's scale: Apr 7 to Oct 29
YOUR Parcel
- ✓Your exact zone, not Mount Union's 5b
- ✓Your SSURGO soil type & pH
- ✓Your sun exposure, cast in 3D
See MY Growing Report
Read your specific parcel in Mount Union
Pull a site-specific report for your exact address in Mount Union, Iowa — soil, sun, drainage, frost risk, and scored plant recommendations.
Three things about your lot that Mount Union averages can't show:
We read public map data around Mount Union — soil, climate, flood, and parcel records. How we handle your address.
25+ data sources read at your address, not the Mount Union average
How we know this about Mount Union
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 Union’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 Union
When does frost risk typically end in Mount Union?
The last hard freeze (28°F) in Mount Union typically lands around Apr 7, 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 Apr 28.
When is the first frost in Mount Union?
The first hard freeze (28°F) in Mount Union 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 205 days after the spring freeze cleared.
How long is the growing season in Mount Union?
Measured between 28°F hard freezes, Mount Union sees about 205 frost-free days — roughly Apr 7 through Oct 29, per NOAA 1991–2020 climate normals. Tender crops work a shorter one: nearer Apr 28 to Oct 15, about 170 days.
Is the soil safe to grow vegetables in Mount Union?
The federal record around Mount Union shows 160 documented sites, mostly Nitrate entries (84), the nearest Underground Storage Tanks record about 0.1 miles out — a typical footprint for a growing area, and proximity to a documented site is information, not a diagnosis of any one yard. It's worth seeing which recorded sites sit closest to where you grow, and testing the soil before new food beds near any of them.
How do I protect my plants from frost in Mount Union?
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 Union's scale — its 5b band and its 205-day season. Your yard writes its own version of Mount Union'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 Union’s own scale
6 of the readings below were taken at Mount Union's own scale — its own ~205-day season between 28°F freezes, the 108 acres it covers and 160 documented sites around it; 4 are borrowed from a wider read, named and linked below.
Measured here
- Mount Union's own USDA hardiness band, zones 5bUSDA PHZM 2023
- Mount Union's own 28°F hard-freeze dates, about Apr 7 and Oct 29 and the ~205-day span between themNOAA 1991–2020 Climate Normals
- 160 documented contamination sites on the federal record near Mount Union, the closest Underground Storage Tanks record about 0.1 miles out from the town centreFederal environmental registers
- Mount Union's boundary and the 108 acres inside itUS Census TIGER/Line 2025
- Which of 1,086 plants clear zones 5b and a ~205-day seasonGrowable Ground crop-matching engine
- The ecoregion at Mount Union's own centroid, the Western Corn Belt PlainsUS EPA Level III Ecoregions
Inherited from a wider read
- Soil character — no town-scale survey exists, so Mount Union's 108 acres read through its county's SSURGO summaryfrom Henry County
- Growing-degree days and winter chill — measured county-wide only, so the county page carries themfrom Henry County
- The growing challenges every Iowa grower plans around — written at state scale, so they stay on the state guidefrom Iowa
- Butterfly and beetle records, and the farmland pesticide estimate — all published county-widefrom Henry County
What this page can’t tell you
- The soil pH, drainage, sun hours, and frost pockets on any one lot among Mount Union's 108 acreswhy one lot differs from the next →
- Which side of Mount Union you're on — a low spot frosts first and a south wall warms early, and one normal is being asked to speak for all 108 acresreading your own microclimate →
- How close that record sits to YOUR lot — the closest Underground Storage Tanks record about 0.1 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 Union-wide figureread your own land →