Delaware County, in Iowa, sits in USDA hardiness zone 5a — a zone band wide enough that plant choice, not possibility, is the interesting question.
Among the crops suited to this profile: cabbage, cranberry, lavender, and collard greens. The site-level story — soil, sun, drainage — decides the rest.
Grounded in USDA PHZM 2023 · Growable Ground suitability scoring · NOAA 1991–2020 Climate Normals
Delaware County holds more than one microclimate.
Soils and elevations shift across Delaware 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 Delaware County — soil, climate, flood, and parcel records. How we handle your address.
No card required · your full report in seconds
Delaware County — the short answer
Delaware County, Iowa: USDA zone 5a, about 173 days between hard freezes, across 370K acres.
- USDA zone
- 5a
- USDA PHZM 2023
- Last hard freeze (28°F)
- Apr 22
- NOAA 1991–2020 Climate Normals, 28°F
- First hard freeze (28°F)
- Oct 12
- NOAA 1991–2020 Climate Normals, 28°F
- Days between freezes
- ~173
- NOAA 1991–2020 Climate Normals, 28°F
- County area
- 370K 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 5a is Delaware County's average, not your lot's — a low corner or a tree line moves it. Against Delaware County's 173-day season, see what your own ground reads.
Heat in Delaware County
Across a year, Delaware County accumulates about 2,428 growing degree days above 50°F, about 316 fewer than the middle Iowa county — ahead of 6 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 Delaware County
Across Delaware County, the ground is predominantly Mollisols, where Kenyon, Fayette, and Clyde 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 C soils.
Soil order
Mollisols
Drainage
Well drained
Prime farmland
37%
Hydric soils
16%
Soil still varies lot by lot — soil types explained.
How the ground varies across Delaware County
The USDA soil survey maps 38% of Delaware County as well drained — but another 61% drains differently: 26% poorly drained, 23% moderately well drained.
Kenyon is the most extensive named soil at 14% of mapped acres, then Fayette (11%) and Clyde (10%).
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 Delaware County
Each reading below is measured for Delaware 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 Delaware County are well drained, in hydrologic group C — 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 Delaware 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 16% of Delaware 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
MeasuredDelaware County runs about 173 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 Delaware County is in
Delaware County spans 2 EPA Level III ecoregions — Western Corn Belt Plains (92%) and Driftless Area (8%). Which one your land falls in changes what grows wild there and how the ground behaves, and a county-wide answer cannot tell you which.
What Grows in Delaware County
We scored all 1,086 plants against Delaware County's own USDA zone 5a and its own 173-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 Delaware County?
Too late for some crops, right on time for others — a growing season is a sequence, not a deadline. Cool-season crops can go in from around Mar 25; tender transplants wait until two to three weeks after the last 28°F hard freeze, which lands near Apr 22 (NOAA 1991–2020 climate normals); and from midsummer, planting counts back from the first fall freeze around Oct 12 — long-season crops need about 90 days of runway, quick greens only 30. Late in the year the fall bench takes over — quick greens, radishes, and garlic that repays you next summer.
Documented around Delaware County
- monarch butterfly406 documented records
Sighting records, so they follow observers as much as insects.
What gets applied to farmland in Delaware County
USGS estimates 254,207 lb of Glyphosate on Delaware County farmland in 2019, its largest by weight, ahead of Acetochlor (155,036 lb) and Atrazine (96,975 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 Delaware County — and how to grow with it.
We checked the federal record across Delaware County — 207 documented sites across 6 of the 9 source types we track.
The most significant on record: 15 Toxics Release Inventory facilities. Active industrial facilities reporting chemical releases to air, water, and land.
There's a meaningful federal record across Delaware 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 Delaware County
Closest first, across Delaware County. Listing isn't leaking, and distance isn't exposure.
- DELAWARE COUNTY ENGINEERUnderground Storage Tanks · 1.1 mi
- GARYS LIQUOR & WINE LTDUnderground Storage Tanks · 1.2 mi
- FAUST GARAGE & GROCERYUnderground Storage Tanks · 1.2 mi
- DEL-CO VET PHARMUnderground Storage Tanks · 2.7 mi
- OCONNELL GRAIN EXPRESSUnderground Storage Tanks · 3.2 mi
- 088N04W17CANitrate · 3.4 mi
- REUFER INSULATIONUnderground Storage Tanks · 3.5 mi
- KWIK STOPUnderground Storage Tanks · 3.5 mi
- HARTWICK LAKE MARINA INCUnderground Storage Tanks · 3.5 mi
- PALADIN ATTACHMENTSBrownfields · 3.5 mi
- PALADIN ATTACHMENTSToxics Release Inventory · 3.5 mi
- 088N04W17DDB 10437 1958Delhi 1Nitrate · 3.6 mi
6 more sites are on the record inside the same radius. See them on the map
Measured from Delaware 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 Delaware County.
Total Sites
207
across Delaware County
Risk Level
Elevated
Highest-severity
15 Toxics Release Inventory facilities
Sources Checked
across Delaware County
Severity Distribution
across Delaware County
Highest-Severity Sites
A note from Gnorman
What an experienced grower watches for around here
In and around Delaware County, Toxics Release Inventory runs higher than the national average — 15 sites across Delaware 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 Delaware 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 Delaware County average
Your land is one point inside Delaware County
Everything above resolves to Delaware County as a whole — one PHZM band and one county frost record, read across 370K 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 Delaware County Average
Delaware County Average
- ●USDA Zones 5a, averaged across Delaware County
- ●One soil character for all of Delaware County
- ●Frost dates read at Delaware County's scale: Apr 22 to Oct 12
YOUR Parcel
- ✓Your exact zone, not Delaware County's 5a
- ✓Your SSURGO soil type & pH
- ✓Your sun exposure, cast in 3D
See MY Growing Report
Read your parcel in Delaware County
Pull a site-specific report for your exact address in Delaware County, Iowa — soil, sun, drainage, frost risk, and scored plant recommendations.
Three things about your lot that Delaware County averages can't show:
We read public map data around Delaware County — soil, climate, flood, and parcel records. How we handle your address.
25+ data sources read at your address, not the Delaware County average
How we know this about Delaware 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 Delaware County carries no record of its own, the figure is inherited and labelled — the resolution ledger below names each.
Common questions about Delaware County
When does frost risk typically end in Delaware County?
The last hard freeze (28°F) in Delaware County typically lands around Apr 22, 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 13.
How long is the growing season in Delaware County?
Measured between 28°F hard freezes, Delaware County sees about 173 frost-free days — roughly Apr 22 through Oct 12, per NOAA 1991–2020 climate normals. Tender crops work a shorter one: nearer May 13 to Sep 28, about 138 days.
Is the soil safe to grow vegetables in Delaware County?
The federal record around Delaware County is a meaningful one — 207 documented sites, mostly Underground Storage Tanks entries (114), the nearest Underground Storage Tanks record about 1.1 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 Delaware County's scale — its 5a band and its 173-day season. Your yard writes its own version of Delaware 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 Delaware County’s own scale
9 of the readings below were taken at Delaware County's own scale — its own ~173-day span between 28°F freezes, the 3 most extensive soil series mapped here and 207 documented sites inside its boundary; one is borrowed from a wider read, named and linked below.
Measured here
- Delaware County's own USDA hardiness band, zones 5aUSDA PHZM 2023
- Delaware County's own 28°F hard-freeze dates and its ~173-day span between themNOAA 1991–2020 Climate Normals
- The soil order, drainage, surface pH, and the 3 most extensive named soil series mapped in Delaware CountyUSDA NRCS SSURGO
- 207 documented contamination sites inside the county boundary, distance-sorted from its center — the closest Underground Storage Tanks record about 1.1 miles outFederal environmental registers
- Delaware County's boundary and the 369,718 acres inside itUS Census TIGER/Line 2025
- Which of 1,086 plants clear zones 5a and a ~173-day seasonGrowable Ground crop-matching engine
- The 2 ecoregions Delaware County spans, Western Corn Belt Plains the largestUS EPA Level III Ecoregions
- Open occurrence records documented in Delaware County for a tracked speciesGBIF derived datasets (CC0 / CC BY 4.0)
- Which agricultural compounds go onto Delaware 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 Delaware County — the ~173 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 Delaware County's 369,718 acreswhy one lot differs from the next →
- Which of those 207 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 Delaware Countyread your own land →