Delphos, 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.
Even in Delphos, 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 Delphos 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 Delphos — soil, climate, flood, and parcel records. How we handle your address.
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Delphos — the short answer
Delphos, Iowa: USDA zone 5b, about 202 days between hard freezes, across 143 acres of town.
- USDA zone
- 5b
- USDA PHZM 2023
- Last hard freeze (28°F)
- Apr 7
- NOAA 1991–2020 Climate Normals, 28°F — this town
- First hard freeze (28°F)
- Oct 26
- NOAA 1991–2020 Climate Normals, 28°F — this town
- Days between freezes
- ~202
- NOAA 1991–2020 Climate Normals, 28°F — this town
- Town area
- 143 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 5b is Delphos's average, not your lot's — a low corner or a tree line moves it. Against Delphos's 202-day season, see what your own ground reads.
Soil varies lot by lot — soil types explained.
What this means for growing in Delphos
Each reading below is measured for Delphos itself — here is what it means for a garden here, and the move an experienced grower makes about it.
Season length
MeasuredDelphos runs about 202 days between hard freezes — a long growing season.
There is slack for succession plantings and slow-finishing crops: many vegetables can be sown twice, and the heat-lovers have time to ripen fully.
Plan a second sowing of quick crops after the first comes out, and use the fall window most gardeners let sit idle.
NOAA 1991–2020 Climate Normals
Winter hardiness
MeasuredDelphos 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 Delphos is in
Delphos sits in the Central Irregular Plains — EPA Level III, inside the wider Great Plains. That is read at Delphos's own centroid rather than borrowed from Ringgold County.
What Grows in Delphos
Every plant below cleared Delphos's own zone 5b and its 202-day season. Each card opens that plant's Iowa profile. How we score.
Is it too late to plant in Delphos?
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 10; tender transplants wait until two to three weeks after the last 28°F hard freeze, which lands near Apr 7 (NOAA 1991–2020 climate normals); and from midsummer, planting counts back from the first fall freeze around Oct 26 — long-season crops need about 90 days of runway, quick greens only 30. There is slack in a calendar like this — late plantings, second rounds of favorites, and a fall bench that keeps beds working.
What's on the federal record near Delphos
Closest first, within ~10 miles of Delphos. Listing isn't leaking, and distance isn't exposure.
- SEATON STOREUnderground Storage Tanks · 150 ft
- 068N30W20CBCNitrate · 0.6 mi
- 068N30W17DDDD 04010 1949Upland Game ReserveNitrate · 1.6 mi
- 067N30W06DDDNitrate · 2.7 mi
- 068N31W12ADA Benton Public SchoolNitrate · 3.1 mi
- HELENA CHEMICAL COMPANYBrownfields · 3.3 mi
- KELLY TIRE & EXHAUSTUnderground Storage Tanks · 3.7 mi
- FORMER HAROLD''S MOBILUnderground Storage Tanks · 5.3 mi
- VETTER EQUIPMENT COBrownfields · 5.3 mi
- IOWA DEPARTMENT OF TRANSPORTATIONBrownfields · 5.5 mi
- GLENDENNING MOTOR CO INCBrownfields · 6.0 mi
- CASEY''S GENERAL STORE 25Underground Storage Tanks · 6.2 mi
6 more sites are on the record inside the same radius. See them on the map
Measured from Delphos'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 Delphos.
Total Sites
48
within ~10 miles of Delphos
Risk Level
Low
Highest-severity
1 Toxics Release Inventory facility
Sources Checked
within ~10 miles of Delphos
Severity Distribution
within ~10 miles of Delphos
Highest-Severity Sites
A note from Gnorman
What an experienced grower watches for around here
In and around Delphos, Nitrate runs higher than the national average — 14 sites within ~10 miles of Delphos. That's not a problem with your land — it's information about it.
Nitrate: Nitrate contamination primarily comes from agricultural fertilizer runoff and failing septic systems.
Test well water for nitrate if you rely on a private well for irrigation (EPA standard: 10 mg/L).
Check your specific parcel in Delphos
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 Delphos average
Your land is one point inside Delphos
Everything above resolves to Delphos as a whole — one PHZM band and one 28°F frost record, read across 143 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 town 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 Delphos Average
Delphos Average
- ●USDA Zones 5b, averaged across Delphos
- ●One soil character for all of Delphos
- ●Frost dates read at Delphos's scale: Apr 7 to Oct 26
YOUR Parcel
- ✓Your exact zone, not Delphos's 5b
- ✓Your SSURGO soil type & pH
- ✓Your sun exposure, cast in 3D
See MY Growing Report
Read your specific parcel in Delphos
Pull a site-specific report for your exact address in Delphos, Iowa — soil, sun, drainage, frost risk, and scored plant recommendations.
Three things about your lot that Delphos averages can't show:
We read public map data around Delphos — soil, climate, flood, and parcel records. How we handle your address.
25+ data sources read at your address, not the Delphos average
How we know this about Delphos
The datasets: hardiness from the USDA ARS Plant Hardiness Zone Map 2023, read at this town’s own centroid; hard-freeze dates from NOAA 1991–2020 28°F normals at Delphos’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 town grain anywhere on this page — there is no town-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 Delphos
When does frost risk typically end in Delphos?
The last hard freeze (28°F) in Delphos typically lands around Apr 7, 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 Apr 28.
When is the first frost in Delphos?
The first hard freeze (28°F) in Delphos typically arrives around Oct 26, per NOAA 1991–2020 climate normals — the point tender summer crops finish. Lighter frosts run ahead of it, near Oct 12, so the watching starts about Sep 26 — about 202 days after the spring freeze cleared.
How long is the growing season in Delphos?
Measured between 28°F hard freezes, Delphos sees about 202 frost-free days — roughly Apr 7 through Oct 26, per NOAA 1991–2020 climate normals. Tender crops work a shorter one: nearer Apr 28 to Oct 12, about 167 days.
Is the soil safe to grow vegetables in Delphos?
The federal record around Delphos is light — 48 documented sites across the 9 federal source types we checked, mostly Underground Storage Tanks entries (21), the nearest Underground Storage Tanks record under a tenth of a mile out — and proximity to a documented site is information, not a diagnosis of any one yard. Growing food here starts from a strong position; a soil test before new food beds settles any site-specific question.
How do I protect my plants from frost in Delphos?
From about Sep 26 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 26 (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 26. Hardy greens and roots shrug off light frost and sweeten after it — leave them in.
Everything above is measured at Delphos's scale — its 5b band and its 202-day season. Your yard writes its own version of Delphos'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 Delphos’s own scale
6 of the readings below were taken at Delphos's own scale — its own ~202-day season between 28°F freezes, the 143 acres it covers and 48 documented sites around it; 4 are borrowed from a wider read, named and linked below.
Measured here
- Delphos's own USDA hardiness band, zones 5bUSDA PHZM 2023
- Delphos's own 28°F hard-freeze dates, about Apr 7 and Oct 26 and the ~202-day span between themNOAA 1991–2020 Climate Normals
- 48 documented contamination sites on the federal record near Delphos, the closest Underground Storage Tanks record under a tenth of a mile out from the town centreFederal environmental registers
- Delphos's boundary and the 143 acres inside itUS Census TIGER/Line 2025
- Which of 1,086 plants clear zones 5b and a ~202-day seasonGrowable Ground crop-matching engine
- The ecoregion at Delphos's own centroid, the Central Irregular PlainsUS EPA Level III Ecoregions
Inherited from a wider read
- Soil character — no town-scale survey exists, so Delphos's 143 acres read through its county's SSURGO summaryfrom Ringgold County
- Growing-degree days and winter chill — measured county-wide only, so the county page carries themfrom Ringgold 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 Ringgold County
What this page can’t tell you
- The soil pH, drainage, sun hours, and frost pockets on any one lot among Delphos's 143 acreswhy one lot differs from the next →
- Which side of Delphos you're on — a low spot frosts first and a south wall warms early, and one normal is being asked to speak for all 143 acresreading your own microclimate →
- How close that record sits to YOUR lot — the closest Underground Storage Tanks record under a tenth of a mile 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 Delphos-wide figureread your own land →
More in Iowa
Wider growing context
What grows across IowaDelphos sits outside our named growing regions, so Iowa as a whole is its closest context here.