Harrison County, in Iowa, sits in USDA hardiness zone 5b — room for a real mix of vegetables, fruit, and perennials matched to the local frost calendar.
A short list that earns its place here — cabbage, cranberry, lavender, and collard greens — with any one site's soil, sun, and drainage making the final cut.
Harrison County lies within the Loess Hills — a regional growing area with its own character.
Grounded in USDA PHZM 2023 · Growable Ground suitability scoring · NOAA 1991–2020 Climate Normals
Harrison County holds more than one microclimate.
Soils and elevations shift across Harrison 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 Harrison County — soil, climate, flood, and parcel records. How we handle your address.
No card required · your full report in seconds
Harrison County — the short answer
Harrison County, Iowa: USDA zone 5b, about 188 days between hard freezes, across 446K acres.
- USDA zone
- 5b
- USDA PHZM 2023
- Last hard freeze (28°F)
- Apr 13
- NOAA 1991–2020 Climate Normals, 28°F
- First hard freeze (28°F)
- Oct 18
- NOAA 1991–2020 Climate Normals, 28°F
- Days between freezes
- ~188
- NOAA 1991–2020 Climate Normals, 28°F
- County area
- 446K 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 5b is Harrison County's average, not your lot's — a low corner or a tree line moves it. Against Harrison County's 188-day season, see what your own ground reads.
Heat in Harrison County
Across a year, Harrison County accumulates about 3,008 growing degree days above 50°F, about 264 more than the middle Iowa county — ahead of 77 of Iowa’s 99 counties. 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 Harrison County
Across Harrison County, the ground is predominantly Mollisols, where Napier, Ida, and Monona are the most extensive named soil series. The soil is generally well drained with a silt loam surface. Topsoil pH runs about 6.2–7.7, neutral. Rainfall drains through hydrologic group B soils.
Soil order
Mollisols
Drainage
Well drained
Prime farmland
31%
Hydric soils
15%
Soil still varies lot by lot — soil types explained.
How the ground varies across Harrison County
The USDA soil survey maps 68% of Harrison County as well drained — but another 31% drains differently: 12% poorly drained, 8% somewhat poorly drained.
Napier is the most extensive named soil at 18% of mapped acres, then Ida (18%) and Monona (13%).
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 Harrison County
Each reading below is measured for Harrison 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 Harrison County are well drained, in hydrologic group B — ground that drains quickly.
The upside is soil you can work early in spring and roots that never drown; the cost is that fast-draining ground dries out fast and leaches nutrients away before plants can use them.
Work in compost and mulch to hold moisture and feed, and water more often in short doses than deep and rarely.
USDA NRCS SSURGO
Surface pH
MeasuredTopsoil across Harrison County runs about pH 6.2–7.7, 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
MeasuredHarrison County runs about 188 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
MeasuredHarrison County 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 Harrison County is in
Harrison 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 Harrison County
We scored all 1,086 plants against Harrison County's own USDA zone 5b and its own 188-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 Harrison County?
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 16; tender transplants wait until two to three weeks after the last 28°F hard freeze, which lands near Apr 13 (NOAA 1991–2020 climate normals); and from midsummer, planting counts back from the first fall freeze around Oct 18 — long-season crops need about 90 days of runway, quick greens only 30. As the window narrows, the plantings just get faster — fall brassicas, then greens, then garlic to finish.
Documented around Harrison County
- Japanese beetle2 documented records
- monarch butterfly74 documented records
Sighting records, so they follow observers as much as insects.
What gets applied to farmland in Harrison County
USGS estimates 353,529 lb of Glyphosate on Harrison County farmland in 2019, its largest by weight, ahead of Acetochlor (131,840 lb) and Metolachlor & Metolachlor-s (114,677 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 Harrison County — and how to grow with it.
We checked the federal record across Harrison County — 154 documented sites across 6 of the 9 source types we track.
The most significant on record: 4 Toxics Release Inventory facilities. Active industrial facilities reporting chemical releases to air, water, and land.
The federal record across Harrison 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 Harrison County
Closest first, across Harrison County. Listing isn't leaking, and distance isn't exposure.
- RICH ELECTRIC COUnderground Storage Tanks · 2.4 mi
- MICHAELS S STATIONUnderground Storage Tanks · 2.4 mi
- SECONDARY ROAD DEPARTMENTUnderground Storage Tanks · 2.5 mi
- AT&T COMMUNICATIONSUnderground Storage Tanks · 2.5 mi
- 080N43W32ACCD 1972Magnolia 1Nitrate · 2.5 mi
- PERFECTION PRESS INCBrownfields · 3.1 mi
- LOGAN-MAGNOLIA SCHOOUnderground Storage Tanks · 3.5 mi
- ROLLING HILLS FARMSUnderground Storage Tanks · 3.5 mi
- ED''S PLACEUnderground Storage Tanks · 3.5 mi
- W R GRACE & COUnderground Storage Tanks · 3.5 mi
- CLARK LIMESTONE COMPANYUnderground Storage Tanks · 3.5 mi
- COUNTY SHOPUnderground Storage Tanks · 3.5 mi
6 more sites are on the record inside the same radius. See them on the map
Measured from Harrison 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 Harrison County.
Total Sites
154
across Harrison County
Risk Level
Moderate
Highest-severity
4 Toxics Release Inventory facilities
Sources Checked
across Harrison County
Severity Distribution
across Harrison County
Highest-Severity Sites
A note from Gnorman
What an experienced grower watches for around here
In and around Harrison County, Underground Storage Tanks runs higher than the national average — 96 sites across Harrison County. Knowing it is half the work — and it's nothing a thoughtful grower can't plan for.
Underground Storage Tanks: Underground storage tanks are the single most common source of soil contamination near homes and gardens.
Use raised beds with imported soil — this eliminates the primary soil-contact pathway.
Check your specific parcel in Harrison 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 Harrison County average
Your land is one point inside Harrison County
Everything above resolves to Harrison County as a whole — one PHZM band and one county frost record, read across 446K 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 Harrison County Average
Harrison County Average
- ●USDA Zones 5b, averaged across Harrison County
- ●One soil character for all of Harrison County
- ●Frost dates read at Harrison County's scale: Apr 13 to Oct 18
YOUR Parcel
- ✓Your exact zone, not Harrison County's 5b
- ✓Your SSURGO soil type & pH
- ✓Your sun exposure, cast in 3D
See MY Growing Report
Read your parcel in Harrison County
Pull a site-specific report for your exact address in Harrison County, Iowa — soil, sun, drainage, frost risk, and scored plant recommendations.
Three things about your lot that Harrison County averages can't show:
We read public map data around Harrison County — soil, climate, flood, and parcel records. How we handle your address.
25+ data sources read at your address, not the Harrison County average
How we know this about Harrison 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 Harrison County carries no record of its own, the figure is inherited and labelled — the resolution ledger below names each.
Common questions about Harrison County
When does frost risk typically end in Harrison County?
The last hard freeze (28°F) in Harrison County typically lands around Apr 13, 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 4.
How long is the growing season in Harrison County?
Measured between 28°F hard freezes, Harrison County sees about 188 frost-free days — roughly Apr 13 through Oct 18, per NOAA 1991–2020 climate normals. Tender crops work a shorter one: nearer May 4 to Oct 4, about 153 days.
Is the soil safe to grow vegetables in Harrison County?
The federal record around Harrison County shows 154 documented sites, mostly Underground Storage Tanks entries (96), the nearest Underground Storage Tanks record about 2.4 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 Harrison County's scale — its 5b band and its 188-day season. Your yard writes its own version of Harrison 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 Harrison County’s own scale
9 of the readings below were taken at Harrison County's own scale — its own ~188-day span between 28°F freezes, the 3 most extensive soil series mapped here and 154 documented sites inside its boundary; one is borrowed from a wider read, named and linked below.
Measured here
- Harrison County's own USDA hardiness band, zones 5bUSDA PHZM 2023
- Harrison County's own 28°F hard-freeze dates and its ~188-day span between themNOAA 1991–2020 Climate Normals
- The soil order, drainage, surface pH, and the 3 most extensive named soil series mapped in Harrison CountyUSDA NRCS SSURGO
- 154 documented contamination sites inside the county boundary, distance-sorted from its center — the closest Underground Storage Tanks record about 2.4 miles outFederal environmental registers
- Harrison County's boundary and the 445,999 acres inside itUS Census TIGER/Line 2025
- Which of 1,086 plants clear zones 5b and a ~188-day seasonGrowable Ground crop-matching engine
- Harrison County sitting wholly inside the Western Corn Belt PlainsUS EPA Level III Ecoregions
- Open occurrence records documented in Harrison County for 2 tracked speciesGBIF derived datasets (CC0 / CC BY 4.0)
- Which agricultural compounds go onto Harrison 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 Harrison County — the ~188 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 Harrison County's 445,999 acreswhy one lot differs from the next →
- Which of those 154 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 Harrison Countyread your own land →