Dallas County, in Iowa, sits in USDA hardiness zone 5b — enough range to grow cool-season vegetables, hardy fruit, and warm-season crops that mature before the first hard frost.
Growers here do well with cabbage, cranberry, lavender, and collard greens — with the usual caveat that any single yard's soil, sun, and drainage cast the deciding vote.
Grounded in USDA PHZM 2023 · Growable Ground suitability scoring · NOAA 1991–2020 Climate Normals
Dallas County holds more than one microclimate.
Soils and elevations shift across Dallas 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 Dallas County — soil, climate, flood, and parcel records. How we handle your address.
No card required · your full report in seconds
Dallas County — the short answer
Dallas County, Iowa: USDA zone 5b, about 194 days between hard freezes, across 376K acres.
- USDA zone
- 5b
- USDA PHZM 2023
- Last hard freeze (28°F)
- Apr 12
- NOAA 1991–2020 Climate Normals, 28°F
- First hard freeze (28°F)
- Oct 23
- NOAA 1991–2020 Climate Normals, 28°F
- Days between freezes
- ~194
- NOAA 1991–2020 Climate Normals, 28°F
- County area
- 376K 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 Dallas County's average, not your lot's — a low corner or a tree line moves it. Against Dallas County's 194-day season, see what your own ground reads.
Heat in Dallas County
Across a year, Dallas County accumulates about 2,933 growing degree days above 50°F, about 189 more than the middle Iowa county — ahead of 65 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 Dallas County
Across Dallas County, the ground is predominantly Mollisols, where Clarion, Canisteo, and Nicollet are the most extensive named soil series. The soil is generally well drained with a loam surface. Topsoil pH runs about 6.2–6.7, slightly acidic. Rainfall drains through hydrologic group B soils.
Soil order
Mollisols
Drainage
Well drained
Prime farmland
44%
Hydric soils
27%
Soil still varies lot by lot — soil types explained.
How the ground varies across Dallas County
The USDA soil survey maps 43% of Dallas County as well drained — but another 56% drains differently: 27% poorly drained, 16% somewhat poorly drained.
Clarion is the most extensive named soil at 31% of mapped acres, then Canisteo (13%) and Nicollet (11%).
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 Dallas County
Each reading below is measured for Dallas 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 Dallas 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 Dallas 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
Wet ground
MeasuredAbout 27% of Dallas County is mapped as hydric — wetland — soil.
If your lot falls in one of those pockets, a standard in-ground bed will fight waterlogging all season, and roots that need air will struggle.
Check how your own ground drains before you dig; raised beds or moisture-loving plantings turn a wet corner from a problem into a niche.
USDA NRCS SSURGO
Season length
MeasuredDallas County runs about 194 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
The kind of country Dallas County is in
Dallas 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 Dallas County
We scored all 1,086 plants against Dallas County's own USDA zone 5b and its own 194-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 Dallas 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 15; tender transplants wait until two to three weeks after the last 28°F hard freeze, which lands near Apr 12 (NOAA 1991–2020 climate normals); and from midsummer, planting counts back from the first fall freeze around Oct 23 — 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 Dallas County
- Japanese beetle3 documented records
- monarch butterfly411 documented records
Sighting records, so they follow observers as much as insects.
What gets applied to farmland in Dallas County
USGS estimates 229,706 lb of Glyphosate on Dallas County farmland in 2019, its largest by weight, ahead of Acetochlor (119,094 lb) and Atrazine (79,584 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 Dallas County — and how to grow with it.
We checked the federal record across Dallas County — 293 documented sites across 6 of the 9 source types we track.
The most significant on record: 1 Superfund site (none NPL-listed). Sites tracked in EPA's Superfund program — from assessment-stage CERCLIS entries to confirmed National Priorities List cleanup sites.
There's a meaningful federal record across Dallas County — worth a look before you plant food, not a reason to hold back from growing. Proximity to a documented site is information, not a diagnosis of any one yard. A soil test before new food beds is the sensible precaution here, and the map shows exactly which sites sit where, so you can see what's actually near you.
Sources: EPA, USGS — 1.8M documented sites tracked nationwide across 9 federal source types.
What's on the federal record near Dallas County
Closest first, across Dallas County. Listing isn't leaking, and distance isn't exposure.
- 080N27W31CDD 03383 1948Dallas Center 18Nitrate · 1400 ft
- 080N27W31DCC 03349 1948Dallas Center 16Nitrate · 1700 ft
- 079N27W06AAC 03212 1948Dallas Center Test 15Nitrate · 2500 ft
- MOSS BROS INCBrownfields · 2.3 mi
- FORMER DON SMITH FACILITYUnderground Storage Tanks · 3.7 mi
- DARLING NATIONAL LLCBrownfields · 3.7 mi
- ANNEAR EQUIPMENT INCBrownfields · 3.8 mi
- MERCURY-PERCIVAL AVENUESuperfund · 3.9 mi
- MODERN MOTORS INCBrownfields · 4.0 mi
- 079N27W02BDDD 00140 1931Dallas Center SchoolNitrate · 4.0 mi
- CASEY''SUnderground Storage Tanks · 4.0 mi
- SPILLERS CONST LIMITEDUnderground Storage Tanks · 4.1 mi
6 more sites are on the record inside the same radius. See them on the map
Measured from Dallas 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 Dallas County.
Total Sites
293
across Dallas County
Risk Level
Elevated
Highest-severity
1 Superfund site (none NPL-listed)
Sources Checked
across Dallas County
Severity Distribution
across Dallas County
Highest-Severity Sites
A note from Gnorman
What an experienced grower watches for around here
In and around Dallas County, two things run higher than the national average across Dallas County — PFAS (6 sites) and Toxics Release Inventory (18 sites). It's not cause for alarm — it's worth knowing, and there's a sensible way to grow around it.
PFAS: PFAS (per- and polyfluoroalkyl substances) are called "forever chemicals" because they do not biodegrade.
Toxics Release Inventory: TRI facilities report annual chemical releases to air, water, and land.
Test irrigation water source — this is the primary pathway for PFAS to reach garden crops.
Check prevailing wind direction — downwind parcels face higher exposure than upwind or crosswind locations.
Check your specific parcel in Dallas 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 Dallas County average
Your land is one point inside Dallas County
Everything above resolves to Dallas County as a whole — one PHZM band and one county frost record, read across 376K 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 Dallas County Average
Dallas County Average
- ●USDA Zones 5b, averaged across Dallas County
- ●One soil character for all of Dallas County
- ●Frost dates read at Dallas County's scale: Apr 12 to Oct 23
YOUR Parcel
- ✓Your exact zone, not Dallas County's 5b
- ✓Your SSURGO soil type & pH
- ✓Your sun exposure, cast in 3D
See MY Growing Report
Read your parcel in Dallas County
Pull a site-specific report for your exact address in Dallas County, Iowa — soil, sun, drainage, frost risk, and scored plant recommendations.
Three things about your lot that Dallas County averages can't show:
We read public map data around Dallas County — soil, climate, flood, and parcel records. How we handle your address.
25+ data sources read at your address, not the Dallas County average
How we know this about Dallas 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 Dallas County carries no record of its own, the figure is inherited and labelled — the resolution ledger below names each.
Common questions about Dallas County
When does frost risk typically end in Dallas County?
The last hard freeze (28°F) in Dallas County typically lands around Apr 12, 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 3.
How long is the growing season in Dallas County?
Measured between 28°F hard freezes, Dallas County sees about 194 frost-free days — roughly Apr 12 through Oct 23, per NOAA 1991–2020 climate normals. Tender crops work a shorter one: nearer May 3 to Oct 9, about 159 days.
Is the soil safe to grow vegetables in Dallas County?
The federal record around Dallas County is a meaningful one — 293 documented sites, mostly Underground Storage Tanks entries (145), the nearest Nitrate 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.
Everything above is measured at Dallas County's scale — its 5b band and its 194-day season. Your yard writes its own version of Dallas 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 Dallas County’s own scale
9 of the readings below were taken at Dallas County's own scale — its own ~194-day span between 28°F freezes, the 3 most extensive soil series mapped here and 293 documented sites inside its boundary; one is borrowed from a wider read, named and linked below.
Measured here
- Dallas County's own USDA hardiness band, zones 5bUSDA PHZM 2023
- Dallas County's own 28°F hard-freeze dates and its ~194-day span between themNOAA 1991–2020 Climate Normals
- The soil order, drainage, surface pH, and the 3 most extensive named soil series mapped in Dallas CountyUSDA NRCS SSURGO
- 293 documented contamination sites inside the county boundary, distance-sorted from its center — the closest Nitrate record about 0.3 miles outFederal environmental registers
- Dallas County's boundary and the 376,467 acres inside itUS Census TIGER/Line 2025
- Which of 1,086 plants clear zones 5b and a ~194-day seasonGrowable Ground crop-matching engine
- Dallas County sitting wholly inside the Western Corn Belt PlainsUS EPA Level III Ecoregions
- Open occurrence records documented in Dallas County for 2 tracked speciesGBIF derived datasets (CC0 / CC BY 4.0)
- Which agricultural compounds go onto Dallas 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 Dallas County — the ~194 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 Dallas County's 376,467 acreswhy one lot differs from the next →
- Which of those 293 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 Dallas Countyread your own land →