Howard County, in Iowa, sits in USDA hardiness zone 4b — enough range to grow cool-season vegetables, hardy fruit, and warm-season crops that mature before the first hard frost.
These conditions suit cabbage, cranberry, turkish rocket, and collard greens — a starting list any specific site will trim or extend with its own soil, sun, and drainage.
Grounded in USDA PHZM 2023 · Growable Ground suitability scoring · NOAA 1991–2020 Climate Normals
Howard County holds more than one microclimate.
Soils and elevations shift across Howard County, so your frost dates and drainage aren't the county average. 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 Howard County — soil, climate, flood, and parcel records. How we handle your address.
No card required · your full report in seconds
Howard County — the short answer
Howard County, Iowa: USDA zone 4b, about 168 days between hard freezes, across 303K acres.
- USDA zone
- 4b
- USDA PHZM 2023
- Last hard freeze (28°F)
- Apr 24
- NOAA 1991–2020 Climate Normals, 28°F
- First hard freeze (28°F)
- Oct 9
- NOAA 1991–2020 Climate Normals, 28°F
- Days between freezes
- ~168
- NOAA 1991–2020 Climate Normals, 28°F
- County area
- 303K acres
- US Census TIGER/Line 2025
Every figure names the dataset it came from. Hard-freeze dates are county 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 4b is Howard County's average, not your lot's — a low corner or a tree line moves it. Against Howard County's 168-day season, see what your own ground reads.
Heat in Howard County
Across a year, Howard County accumulates about 2,221 growing degree days above 50°F, about 523 fewer than the middle Iowa county — no other Iowa county banks fewer. Degree days are the heat a crop actually gets to work with — more of them is more room to ripen a long-season crop before the freeze closes the window.
Grounded in PRISM Climate Group, Oregon State University — 1991–2020 monthly normals
Soil in Howard County
Across Howard County, the ground is predominantly Mollisols, where Clyde, Floyd, and Bassett are the most extensive named soil series. The soil is generally somewhat poorly drained with a loam surface. Topsoil pH runs about 6.2–6.7, slightly acidic. Rainfall drains through hydrologic group C/D soils.
Soil order
Mollisols
Drainage
Somewhat poorly drained
Prime farmland
62%
Hydric soils
20%
Soil still varies lot by lot — soil types explained.
How the ground varies across Howard County
The USDA soil survey maps 33% of Howard County as somewhat poorly drained — but another 67% drains differently: 23% poorly drained, 22% well drained.
Clyde is the most extensive named soil at 15% of mapped acres, then Floyd (14%) and Bassett (7%).
Which of them your own lot sits on is a parcel question, not a county one. Check your address for the survey at your boundary.
What this means for growing in Howard County
Each reading below is measured for Howard County itself — here is what it means for a garden here, and the move an experienced grower makes about it.
Drainage
MeasuredThe dominant soils across Howard County are somewhat poorly drained, in hydrologic group C/D — ground that sheds water slowly.
Beds can stay saturated for days after heavy rain, and the roots of most vegetables, berries, and fruit trees suffocate or rot in soil that never drains.
Raised beds or mounded rows lift roots above the wet zone; choose water-tolerant crops for the lowest spots.
USDA NRCS SSURGO
Surface pH
MeasuredTopsoil across Howard County runs about pH 6.2–6.7, close to neutral.
This is the range most vegetables prefer — one correction you probably do not have to make, which is genuinely good news for a new bed.
Keep it there with compost rather than lime or sulfur, and only amend if your own soil test says otherwise.
USDA NRCS SSURGO
Season length
MeasuredHoward County runs about 168 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
MeasuredHoward County sits in USDA hardiness zone 4b.
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 Howard County is in
Howard County sits in the Western Corn Belt Plains — EPA Level III, inside the wider Great Plains. One consistent ecological setting across the whole county.
What Grows in Howard County
We scored all 1,086 plants against Howard County's own USDA zone 4b and its own 168-day season between hard freezes, using the same matching engine that runs a full parcel report. These cleared both. Sun, soil pH and drainage vary lot by lot — those are the parcel questions below. Each card opens that plant's Iowa profile.
Is it too late to plant in Howard County?
Usually not — gardeners here simply switch what goes in the ground as the season moves. Cool-season crops can go in from around Mar 27; tender transplants wait until two to three weeks after the last 28°F hard freeze, which lands near Apr 24 (NOAA 1991–2020 climate normals); and from midsummer, planting counts back from the first fall freeze around Oct 9 — long-season crops need about 90 days of runway, quick greens only 30. The tail of the season still works: sixty-day crops into late summer, quick greens after, garlic last of all.
Documented around Howard County
- monarch butterfly573 documented records
Sighting records, so they follow observers as much as insects.
What gets applied to farmland in Howard County
USGS estimates 210,634 lb of Glyphosate on Howard County farmland in 2019, its largest by weight, ahead of Acetochlor (109,239 lb) and Atrazine (64,283 lb).
Farmland across the whole county, not any one lot. Check your address for the site-by-site record.
Safe to Grow Here?
What the federal record shows across Howard County — and how to grow with it.
We checked the federal record across Howard County — 114 documented sites across 5 of the 9 source types we track.
The most significant on record: 9 Toxics Release Inventory facilities. Active industrial facilities reporting chemical releases to air, water, and land.
The federal record across Howard County is a modest one — a typical footprint for a growing area. Nothing here calls for alarm; it's worth knowing which recorded sites sit closest to where you grow, and each one on the map carries its type and location. If one turns out to be a near neighbor, a one-time soil test settles the question.
Sources: EPA, USGS — 1.8M documented sites tracked nationwide across 9 federal source types.
What's on the federal record near Howard County
Closest first, across Howard County. Listing isn't leaking, and distance isn't exposure.
- AG-VANTAGE FSUnderground Storage Tanks · 1.5 mi
- AGVANTAGE FS - DAVIS CORNERSBrownfields · 1.5 mi
- ITC TRANSMISSION - MIDWEST RICE STATIONBrownfields · 2.7 mi
- 098N13W10BDDB 30406 1989Nitrate · 3.8 mi
- MEHMERT TILING INCUnderground Storage Tanks · 4.1 mi
- 100N12W29DBD 1968Lime Springs 2Nitrate · 5.9 mi
- CROELL REDI-MIX INC. (LIMESPRGS)Toxics Release Inventory · 5.9 mi
- 100N12W29DBDC 01836 1944Lime Springs 1Nitrate · 5.9 mi
- CASEYS GENERAL STORE 3439Underground Storage Tanks · 6.0 mi
- A & K FEED & GRAIN COUnderground Storage Tanks · 6.0 mi
- WINNESHIEK COOPERATIVEUnderground Storage Tanks · 6.1 mi
- TANK & TUMMYUnderground Storage Tanks · 6.1 mi
6 more sites are on the record inside the same radius. See them on the map
Measured from Howard County'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 Howard County.
Total Sites
114
across Howard County
Risk Level
Moderate
Highest-severity
9 Toxics Release Inventory facilities
Sources Checked
across Howard County
Severity Distribution
across Howard County
Highest-Severity Sites
A note from Gnorman
What an experienced grower watches for around here
In and around Howard County, Toxics Release Inventory runs higher than the national average — 9 sites across Howard County. Knowing it is half the work — and it's nothing a thoughtful grower can't plan for.
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 Howard County
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 Howard County average
Your land is one point inside Howard County
Everything above resolves to Howard County as a whole — one PHZM band and one county frost record, read across 303K 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 county 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 county average.
Your Lot vs the Howard County Average
Howard County Average
- ●USDA Zones 4b, averaged across Howard County
- ●One soil character for all of Howard County
- ●Frost dates read at Howard County's scale: Apr 24 to Oct 9
YOUR Parcel
- ✓Your exact zone, not Howard County's 4b
- ✓Your SSURGO soil type & pH
- ✓Your sun exposure, cast in 3D
See MY Growing Report
Read your parcel in Howard County
Pull a site-specific report for your exact address in Howard County, Iowa — soil, sun, drainage, frost risk, and scored plant recommendations.
Three things about your lot that Howard County averages can't show:
We read public map data around Howard County — soil, climate, flood, and parcel records. How we handle your address.
25+ data sources read at your address, not the Howard County average
How we know this about Howard County
The datasets: hardiness from the USDA ARS Plant Hardiness Zone Map 2023, read at county grain; hard-freeze dates from NOAA 1991–2020 28°F normals at this county’s own record where one resolves, and the labelled statewide window where none does; soils from the USDA NRCS SSURGO survey, area-weighted across the county’s own map units; boundaries and acreage from US Census TIGER/Line 2025; the contamination and pesticide records from the federal sources named in their beats above. Where Howard County carries no record of its own, the figure is inherited and labelled — the resolution ledger below names each.
Common questions about Howard County
When does frost risk typically end in Howard County?
The last hard freeze (28°F) in Howard County typically lands around Apr 24, 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 15.
How long is the growing season in Howard County?
Measured between 28°F hard freezes, Howard County sees about 168 frost-free days — roughly Apr 24 through Oct 9, per NOAA 1991–2020 climate normals. Tender crops work a shorter one: nearer May 15 to Sep 25, about 133 days.
Is the soil safe to grow vegetables in Howard County?
The federal record around Howard County shows 114 documented sites, mostly Underground Storage Tanks entries (68), the nearest Underground Storage Tanks record about 1.5 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.
Everything above is measured at Howard County's scale — its 4b band and its 168-day season. Your yard writes its own version of Howard County's numbers: we read soil, sun, drainage and frost at your exact address. Try it for 14 days — no card required.
Will It Grow Here?
Zone fit is the first question — each answer below reads Iowa's frost window, season length, and soil profile against the plant's real requirements.
What this page reads at Howard County’s own scale
9 of the readings below were taken at Howard County's own scale — its own ~168-day span between 28°F freezes, the 3 most extensive soil series mapped here and 114 documented sites inside its boundary; one is borrowed from a wider read, named and linked below.
Measured here
- Howard County's own USDA hardiness band, zones 4bUSDA PHZM 2023
- Howard County's own 28°F hard-freeze dates and its ~168-day span between themNOAA 1991–2020 Climate Normals
- The soil order, drainage, surface pH, and the 3 most extensive named soil series mapped in Howard CountyUSDA NRCS SSURGO
- 114 documented contamination sites inside the county boundary, distance-sorted from its center — the closest Underground Storage Tanks record about 1.5 miles outFederal environmental registers
- Howard County's boundary and the 302,877 acres inside itUS Census TIGER/Line 2025
- Which of 1,086 plants clear zones 4b and a ~168-day seasonGrowable Ground crop-matching engine
- Howard County sitting wholly inside the Western Corn Belt PlainsUS EPA Level III Ecoregions
- Open occurrence records documented in Howard County for a tracked speciesGBIF derived datasets (CC0 / CC BY 4.0)
- Which agricultural compounds go onto Howard County farmland, and roughly how muchUSGS NAWQA EPest county estimates
Inherited from a wider read
- The growing challenges every Iowa grower plans around — written at state scale, so they stay on the state guidefrom Iowa
What this page can’t tell you
- How the season shifts across Howard County — the ~168 days above is one reading at its centre; the 12 towns below each carry their owntowns in this county →
- The soil pH, drainage, sun hours, and frost pockets on any one lot among Howard County's 302,877 acreswhy one lot differs from the next →
- Which of those 114 documented sites actually reaches your soil — that needs your address, the wind, and the groundwater directionhow we read the record →
- Where cold air settles, which slopes face the sun, and which way the wind runs on your own ground — none of it survives being averaged over Howard Countyread your own land →