Hamilton, Iowa, sits in USDA hardiness zone 5b — a band that supports both cool-season staples and warm-season crops chosen to fit the local frost window.
Well-matched crops include cabbage, cranberry, lavender, and collard greens, and the gap between "grows in the area" and "grows in your yard" is closed by soil, sun, and drainage.
Even in Hamilton, 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 Hamilton 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 Hamilton — soil, climate, flood, and parcel records. How we handle your address.
No card required · your full report in seconds
Hamilton — the short answer
Hamilton, Iowa: USDA zone 5b, about 202 days between hard freezes, across 324 acres of city.
- 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 26
- NOAA 1991–2020 Climate Normals, 28°F — this town
- Days between freezes
- ~202
- NOAA 1991–2020 Climate Normals, 28°F — this town
- City area
- 324 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 Hamilton's average, not your lot's — a low corner or a tree line moves it. Against Hamilton's 202-day season, see what your own ground reads.
Soil varies lot by lot — soil types explained.
What this means for growing in Hamilton
Each reading below is measured for Hamilton itself — here is what it means for a garden here, and the move an experienced grower makes about it.
Season length
MeasuredHamilton 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
MeasuredHamilton 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 Hamilton is in
Hamilton sits in the Central Irregular Plains — EPA Level III, inside the wider Great Plains. That is read at Hamilton's own centroid, and it is not what its county reads: Marion County is mostly Western Corn Belt Plains. The wider page above you is answering a different question about different ground.
What Grows in Hamilton
Every plant below cleared Hamilton's own zone 5b and its 202-day season. Each card opens that plant's Iowa profile. How we score.
Is it too late to plant in Hamilton?
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 26 — 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 Hamilton
Closest first, within ~10 miles of Hamilton. Listing isn't leaking, and distance isn't exposure.
- WARDS REPAIRUnderground Storage Tanks · 1400 ft
- 074N18W25BAB 21305 1968Nitrate · 1.7 mi
- 074N18W22CAA 21930 1969Nitrate · 1.8 mi
- 074N18W24DD 1918Nitrate · 2.2 mi
- 074N18W24BBA 1934Bussey SchoolNitrate · 2.4 mi
- 074N18W24BA 00368 1936Bussey Test 2Nitrate · 2.4 mi
- LOVILIA TIRE SERVICEUnderground Storage Tanks · 2.4 mi
- LOVILIA BAIT & TIREUnderground Storage Tanks · 2.4 mi
- 073N18W05AAA 19736 1967Nitrate · 2.4 mi
- CASEY''S GENERAL STORE 1327Underground Storage Tanks · 2.4 mi
- TWIN CEDARS COMM SCHOOLSUnderground Storage Tanks · 2.5 mi
- WILSON''S CORNER MINI MARTUnderground Storage Tanks · 2.5 mi
6 more sites are on the record inside the same radius. See them on the map
Measured from Hamilton'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 Hamilton.
Total Sites
113
within ~10 miles of Hamilton
Risk Level
Moderate
Highest-severity
1 Toxics Release Inventory facility
Sources Checked
within ~10 miles of Hamilton
Severity Distribution
within ~10 miles of Hamilton
Highest-Severity Sites
A note from Gnorman
What an experienced grower watches for around here
In and around Hamilton, Nitrate runs higher than the national average — 90 sites within ~10 miles of Hamilton. It's not cause for alarm — it's worth knowing, and there's a sensible way to grow around 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 Hamilton
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 Hamilton average
Your land is one point inside Hamilton
Everything above resolves to Hamilton as a whole — one PHZM band and one 28°F frost record, read across 324 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 city 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 Hamilton Average
Hamilton Average
- ●USDA Zones 5b, averaged across Hamilton
- ●One soil character for all of Hamilton
- ●Frost dates read at Hamilton's scale: Apr 7 to Oct 26
YOUR Parcel
- ✓Your exact zone, not Hamilton's 5b
- ✓Your SSURGO soil type & pH
- ✓Your sun exposure, cast in 3D
See MY Growing Report
Read your specific parcel in Hamilton
Pull a site-specific report for your exact address in Hamilton, Iowa — soil, sun, drainage, frost risk, and scored plant recommendations.
Three things about your lot that Hamilton averages can't show:
We read public map data around Hamilton — soil, climate, flood, and parcel records. How we handle your address.
25+ data sources read at your address, not the Hamilton average
How we know this about Hamilton
The datasets: hardiness from the USDA ARS Plant Hardiness Zone Map 2023, read at this city’s own centroid; hard-freeze dates from NOAA 1991–2020 28°F normals at Hamilton’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 city grain anywhere on this page — there is no city-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 Hamilton
When does frost risk typically end in Hamilton?
The last hard freeze (28°F) in Hamilton 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 Hamilton?
The first hard freeze (28°F) in Hamilton typically arrives around Oct 26, per NOAA 1991–2020 climate normals — the point tender summer crops finish. Lighter frosts run ahead of it, near Oct 12, so the watching starts about Sep 26 — about 202 days after the spring freeze cleared.
How long is the growing season in Hamilton?
Measured between 28°F hard freezes, Hamilton sees about 202 frost-free days — roughly Apr 7 through Oct 26, per NOAA 1991–2020 climate normals. Tender crops work a shorter one: nearer Apr 28 to Oct 12, about 167 days.
Is the soil safe to grow vegetables in Hamilton?
The federal record around Hamilton shows 113 documented sites, mostly Nitrate entries (90), the nearest Underground Storage Tanks record about 0.3 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 Hamilton?
From about Sep 26 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 26 (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 26. Hardy greens and roots shrug off light frost and sweeten after it — leave them in.
Everything above is measured at Hamilton's scale — its 5b band and its 202-day season. Your yard writes its own version of Hamilton'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 Hamilton’s own scale
6 of the readings below were taken at Hamilton's own scale — its own ~202-day season between 28°F freezes, the 324 acres it covers and 113 documented sites around it; 4 are borrowed from a wider read, named and linked below.
Measured here
- Hamilton's own USDA hardiness band, zones 5bUSDA PHZM 2023
- Hamilton's own 28°F hard-freeze dates, about Apr 7 and Oct 26 and the ~202-day span between themNOAA 1991–2020 Climate Normals
- 113 documented contamination sites on the federal record near Hamilton, the closest Underground Storage Tanks record about 0.3 miles out from the town centreFederal environmental registers
- Hamilton's boundary and the 324 acres inside itUS Census TIGER/Line 2025
- Which of 1,086 plants clear zones 5b and a ~202-day seasonGrowable Ground crop-matching engine
- Hamilton sits in the Central Irregular Plains — not the ecoregion its county mostly readsUS EPA Level III Ecoregions
Inherited from a wider read
- Soil character — no town-scale survey exists, so Hamilton's 324 acres read through its county's SSURGO summaryfrom Marion County
- Growing-degree days and winter chill — measured county-wide only, so the county page carries themfrom Marion 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 Marion County
What this page can’t tell you
- The soil pH, drainage, sun hours, and frost pockets on any one lot among Hamilton's 324 acreswhy one lot differs from the next →
- Which side of Hamilton you're on — a low spot frosts first and a south wall warms early, and one normal is being asked to speak for all 324 acresreading your own microclimate →
- How close that record sits to YOUR lot — the closest Underground Storage Tanks record about 0.3 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 Hamilton-wide figureread your own land →
More in Iowa
Wider growing context
What grows across IowaHamilton sits outside our named growing regions, so Iowa as a whole is its closest context here.
Nearby growing guides