Marshalltown, Iowa, sits in USDA hardiness zone 5a — a range where zone-matched perennials and frost-aware annual timing set what succeeds.
Expect cabbage, cranberry, lavender, and collard greens to be strong candidates here; the deciding factors on any one parcel stay local — soil, sun, and drainage.
Even in Marshalltown, 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 Marshalltown 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 Marshalltown — soil, climate, flood, and parcel records. How we handle your address.
No card required · your full report in seconds
Marshalltown — the short answer
Marshalltown, Iowa: USDA zone 5a, about 190 days between hard freezes, across 12K acres of city.
- USDA zone
- 5a
- USDA PHZM 2023
- Last hard freeze (28°F)
- Apr 14
- NOAA 1991–2020 Climate Normals, 28°F — this town
- First hard freeze (28°F)
- Oct 21
- NOAA 1991–2020 Climate Normals, 28°F — this town
- Days between freezes
- ~190
- NOAA 1991–2020 Climate Normals, 28°F — this town
- City area
- 12K 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 5a is Marshalltown's average, not your lot's — a low corner or a tree line moves it. Against Marshalltown's 190-day season, see what your own ground reads.
Soil varies lot by lot — soil types explained.
What this means for growing in Marshalltown
Each reading below is measured for Marshalltown itself — here is what it means for a garden here, and the move an experienced grower makes about it.
Season length
MeasuredMarshalltown runs about 190 days between hard freezes — a moderate growing season.
There is room for the full run of cool-season crops plus a warm-season main crop, but the calendar is tight enough that a late spring or early fall frost still decides how much finishes.
Time warm-season transplants to your last hard freeze, and a few weeks of season extension turns a near-miss harvest into a sure one.
NOAA 1991–2020 Climate Normals
Winter hardiness
MeasuredMarshalltown sits in USDA hardiness zone 5a.
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 Marshalltown is in
Marshalltown sits in the Western Corn Belt Plains — EPA Level III, inside the wider Great Plains. That is read at Marshalltown's own centroid rather than borrowed from Marshall County.
What Grows in Marshalltown
Every plant below cleared Marshalltown's own zone 5a and its 190-day season. Each card opens that plant's Iowa profile. How we score.
Is it too late to plant in Marshalltown?
Rarely: the season closes in stages, not all at once, and each stage has its crops. Cool-season crops can go in from around Mar 17; tender transplants wait until two to three weeks after the last 28°F hard freeze, which lands near Apr 14 (NOAA 1991–2020 climate normals); and from midsummer, planting counts back from the first fall freeze around Oct 21 — long-season crops need about 90 days of runway, quick greens only 30. Even past midsummer there is room for a true fall garden here, and garlic planted near the close carries the momentum into next year.
What's on the federal record near Marshalltown
Closest first, within ~10 miles of Marshalltown. Listing isn't leaking, and distance isn't exposure.
- KENNS AUTO SERVICEBrownfields · 1400 ft
- KWIK STAR #706Underground Storage Tanks · 1600 ft
- ARNOLD MOTOR SUPPLYBrownfields · 1600 ft
- DIAMOND VOGEL PAINTSToxics Release Inventory · 1700 ft
- MARSHALL CONCRETE PRODUCTS COUnderground Storage Tanks · 1800 ft
- UNION PACIFIC RAILYARDUnderground Storage Tanks · 1800 ft
- CITY OF MARSHALLTOWN IOWAUnderground Storage Tanks · 1900 ft
- MARSHALLTOWN CSD SENIOR HIGH AUTO MECHANICSUnderground Storage Tanks · 1900 ft
- OREILLY AUTO PARTS STORE 383Brownfields · 1900 ft
- MARSHALLTOWN STREET DEPT, CITY OFBrownfields · 1900 ft
- MARSHALLTOWN COMM DIST SCH SENIOR HIGHUnderground Storage Tanks · 2000 ft
- MARSHALLTOWN HIGH SCHOOLBrownfields · 2100 ft
6 more sites are on the record inside the same radius. See them on the map
Measured from Marshalltown'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 Marshalltown.
Total Sites
320
within ~10 miles of Marshalltown
Risk Level
Elevated
Highest-severity
3 Superfund sites (none NPL-listed)
Sources Checked
within ~10 miles of Marshalltown
Severity Distribution
within ~10 miles of Marshalltown
Highest-Severity Sites
A note from Gnorman
What an experienced grower watches for around here
In and around Marshalltown, Toxics Release Inventory runs higher than the national average — 28 sites within ~10 miles of Marshalltown. It's not cause for alarm — it's worth knowing, and there's a sensible way to grow around it.
Toxics Release Inventory: TRI facilities report annual chemical releases to air, water, and land.
Check prevailing wind direction — downwind parcels face higher exposure than upwind or crosswind locations.
Check your specific parcel in Marshalltown
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 Marshalltown average
Your land is one point inside Marshalltown
Everything above resolves to Marshalltown as a whole — one PHZM band and one 28°F frost record, read across 12K 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 Marshalltown Average
Marshalltown Average
- ●USDA Zones 5a, averaged across Marshalltown
- ●One soil character for all of Marshalltown
- ●Frost dates read at Marshalltown's scale: Apr 14 to Oct 21
YOUR Parcel
- ✓Your exact zone, not Marshalltown's 5a
- ✓Your SSURGO soil type & pH
- ✓Your sun exposure, cast in 3D
See MY Growing Report
Read your specific parcel in Marshalltown
Pull a site-specific report for your exact address in Marshalltown, Iowa — soil, sun, drainage, frost risk, and scored plant recommendations.
Three things about your lot that Marshalltown averages can't show:
We read public map data around Marshalltown — soil, climate, flood, and parcel records. How we handle your address.
25+ data sources read at your address, not the Marshalltown average
How we know this about Marshalltown
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 Marshalltown’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 Marshalltown
When does frost risk typically end in Marshalltown?
The last hard freeze (28°F) in Marshalltown typically lands around Apr 14, 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 5.
When is the first frost in Marshalltown?
The first hard freeze (28°F) in Marshalltown typically arrives around Oct 21, per NOAA 1991–2020 climate normals — the point tender summer crops finish. Lighter frosts run ahead of it, near Oct 7, so the watching starts about Sep 21 — about 190 days after the spring freeze cleared.
How long is the growing season in Marshalltown?
Measured between 28°F hard freezes, Marshalltown sees about 190 frost-free days — roughly Apr 14 through Oct 21, per NOAA 1991–2020 climate normals. Tender crops work a shorter one: nearer May 5 to Oct 7, about 155 days.
Is the soil safe to grow vegetables in Marshalltown?
The federal record around Marshalltown is a meaningful one — 320 documented sites, mostly Underground Storage Tanks entries (157), the nearest Brownfields record about 0.3 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 Marshalltown?
From about Sep 21 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 21 (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 21. Hardy greens and roots shrug off light frost and sweeten after it — leave them in.
Everything above is measured at Marshalltown's scale — its 5a band and its 190-day season. Your yard writes its own version of Marshalltown'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 Marshalltown’s own scale
6 of the readings below were taken at Marshalltown's own scale — its own ~190-day season between 28°F freezes, the 12,287 acres it covers and 320 documented sites around it; 4 are borrowed from a wider read, named and linked below.
Measured here
- Marshalltown's own USDA hardiness band, zones 5aUSDA PHZM 2023
- Marshalltown's own 28°F hard-freeze dates, about Apr 14 and Oct 21 and the ~190-day span between themNOAA 1991–2020 Climate Normals
- 320 documented contamination sites on the federal record near Marshalltown, the closest Brownfields record about 0.3 miles out from the town centreFederal environmental registers
- Marshalltown's boundary and the 12,287 acres inside itUS Census TIGER/Line 2025
- Which of 1,086 plants clear zones 5a and a ~190-day seasonGrowable Ground crop-matching engine
- The ecoregion at Marshalltown'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 Marshalltown's 12,287 acres read through its county's SSURGO summaryfrom Marshall County
- Growing-degree days and winter chill — measured county-wide only, so the county page carries themfrom Marshall 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 Marshall County
What this page can’t tell you
- The soil pH, drainage, sun hours, and frost pockets on any one lot among Marshalltown's 12,287 acreswhy one lot differs from the next →
- Which side of Marshalltown you're on — a low spot frosts first and a south wall warms early, and one normal is being asked to speak for all 12,287 acresreading your own microclimate →
- How close that record sits to YOUR lot — the closest Brownfields 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 Marshalltown-wide figureread your own land →
More in Iowa
Wider growing context
What grows across IowaMarshalltown sits outside our named growing regions, so Iowa as a whole is its closest context here.
Nearby growing guides