Dahlgren, Illinois, sits in USDA hardiness zone 6b — enough range to grow cool-season vegetables, hardy fruit, and warm-season crops that mature before the first hard frost.
On paper, cabbage, hazelnut, lavender, and collard greens all suit these conditions — on the ground, soil, sun, and drainage make the final call.
Even in Dahlgren, 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 Dahlgren 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 Dahlgren — soil, climate, flood, and parcel records. How we handle your address.
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Dahlgren — the short answer
Dahlgren, Illinois: USDA zone 6b, about 218 days between hard freezes, across 651 acres of town.
- USDA zone
- 6b
- USDA PHZM 2023
- Last hard freeze (28°F)
- Mar 29
- NOAA 1991–2020 Climate Normals, 28°F — this town
- First hard freeze (28°F)
- Nov 2
- NOAA 1991–2020 Climate Normals, 28°F — this town
- Days between freezes
- ~218
- NOAA 1991–2020 Climate Normals, 28°F — this town
- Town area
- 651 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 6b is Dahlgren's average, not your lot's — a low corner or a tree line moves it. Against Dahlgren's 218-day season, see what your own ground reads.
Soil varies lot by lot — soil types explained.
What this means for growing in Dahlgren
Each reading below is measured for Dahlgren itself — here is what it means for a garden here, and the move an experienced grower makes about it.
Season length
MeasuredDahlgren runs about 218 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
MeasuredDahlgren sits in USDA hardiness zone 6b.
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 Dahlgren is in
Dahlgren sits in the Interior River Valleys and Hills — EPA Level III, inside the wider Eastern Temperate Forests. That is read at Dahlgren's own centroid rather than borrowed from Hamilton County.
What Grows in Dahlgren
Every plant below cleared Dahlgren's own zone 6b and its 218-day season. Each card opens that plant's Illinois profile. How we score.
Is it too late to plant in Dahlgren?
For most of the year, no — what changes is which crops still fit the days remaining. Cool-season crops can go in from around Mar 1; tender transplants wait until two to three weeks after the last 28°F hard freeze, which lands near Mar 29 (NOAA 1991–2020 climate normals); and from midsummer, planting counts back from the first fall freeze around Nov 2 — 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 Dahlgren
Closest first, within ~10 miles of Dahlgren. Listing isn't leaking, and distance isn't exposure.
- Frank Zachman FertilizerUnderground Storage Tanks · 50 ft
- United Il BankUnderground Storage Tanks · 50 ft
- Tonya SpicuzzaUnderground Storage Tanks · 1100 ft
- Dahlgren Attendance CtrUnderground Storage Tanks · 1300 ft
- Irwin WillienUnderground Storage Tanks · 1600 ft
- Hamson's Trading PostUnderground Storage Tanks · 1.1 mi
- Stoltz LloydUnderground Storage Tanks · 2.1 mi
- Karcher ServUnderground Storage Tanks · 2.1 mi
- TAYLOR-ATKINSON INCBrownfields · 2.9 mi
- Gateway FSUnderground Storage Tanks · 3.6 mi
- Murrel Bernard Grain ElevatorUnderground Storage Tanks · 3.8 mi
- Ten Mile Creek Eads UnitUnderground Storage Tanks · 3.8 mi
6 more sites are on the record inside the same radius. See them on the map
Measured from Dahlgren'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 Dahlgren.
Total Sites
28
within ~10 miles of Dahlgren
Risk Level
Low
Highest-severity
2 concentrated animal feeding operations
Sources Checked
within ~10 miles of Dahlgren
Severity Distribution
within ~10 miles of Dahlgren
Highest-Severity Sites
A note from Gnorman
What an experienced grower watches for around here
In and around Dahlgren, Underground Storage Tanks runs higher than the national average — 22 sites within ~10 miles of Dahlgren. It's not cause for alarm — it's worth knowing, and there's a sensible way to grow around it.
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 Dahlgren
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 Dahlgren average
Your land is one point inside Dahlgren
Everything above resolves to Dahlgren as a whole — one PHZM band and one 28°F frost record, read across 651 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 Dahlgren Average
Dahlgren Average
- ●USDA Zones 6b, averaged across Dahlgren
- ●One soil character for all of Dahlgren
- ●Frost dates read at Dahlgren's scale: Mar 29 to Nov 2
YOUR Parcel
- ✓Your exact zone, not Dahlgren's 6b
- ✓Your SSURGO soil type & pH
- ✓Your sun exposure, cast in 3D
See MY Growing Report
Read your specific parcel in Dahlgren
Pull a site-specific report for your exact address in Dahlgren, Illinois — soil, sun, drainage, frost risk, and scored plant recommendations.
Three things about your lot that Dahlgren averages can't show:
We read public map data around Dahlgren — soil, climate, flood, and parcel records. How we handle your address.
25+ data sources read at your address, not the Dahlgren average
How we know this about Dahlgren
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 Dahlgren’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 Dahlgren
When does frost risk typically end in Dahlgren?
The last hard freeze (28°F) in Dahlgren typically lands around Mar 29, 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 19.
When is the first frost in Dahlgren?
The first hard freeze (28°F) in Dahlgren typically arrives around Nov 2, per NOAA 1991–2020 climate normals — the point tender summer crops finish. Lighter frosts run ahead of it, near Oct 19, so the watching starts about Oct 3 — about 218 days after the spring freeze cleared.
How long is the growing season in Dahlgren?
Measured between 28°F hard freezes, Dahlgren sees about 218 frost-free days — roughly Mar 29 through Nov 2, per NOAA 1991–2020 climate normals. Tender crops work a shorter one: nearer Apr 19 to Oct 19, about 183 days.
Is the soil safe to grow vegetables in Dahlgren?
The federal record around Dahlgren is light — 28 documented sites across the 9 federal source types we checked, mostly Underground Storage Tanks entries (22), 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 Dahlgren?
From about Oct 3 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 Nov 2 (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 Nov 2. Hardy greens and roots shrug off light frost and sweeten after it — leave them in.
Everything above is measured at Dahlgren's scale — its 6b band and its 218-day season. Your yard writes its own version of Dahlgren'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 Dahlgren’s own scale
6 of the readings below were taken at Dahlgren's own scale — its own ~218-day season between 28°F freezes, the 651 acres it covers and 28 documented sites around it; 4 are borrowed from a wider read, named and linked below.
Measured here
- Dahlgren's own USDA hardiness band, zones 6bUSDA PHZM 2023
- Dahlgren's own 28°F hard-freeze dates, about Mar 29 and Nov 2 and the ~218-day span between themNOAA 1991–2020 Climate Normals
- 28 documented contamination sites on the federal record near Dahlgren, the closest Underground Storage Tanks record under a tenth of a mile out from the town centreFederal environmental registers
- Dahlgren's boundary and the 651 acres inside itUS Census TIGER/Line 2025
- Which of 1,086 plants clear zones 6b and a ~218-day seasonGrowable Ground crop-matching engine
- The ecoregion at Dahlgren's own centroid, the Interior River Valleys and HillsUS EPA Level III Ecoregions
Inherited from a wider read
- Soil character — no town-scale survey exists, so Dahlgren's 651 acres read through its county's SSURGO summaryfrom Hamilton County
- Growing-degree days and winter chill — measured county-wide only, so the county page carries themfrom Hamilton County
- The growing challenges every Illinois grower plans around — written at state scale, so they stay on the state guidefrom Illinois
- Butterfly and beetle records, and the farmland pesticide estimate — all published county-widefrom Hamilton County
What this page can’t tell you
- The soil pH, drainage, sun hours, and frost pockets on any one lot among Dahlgren's 651 acreswhy one lot differs from the next →
- Which side of Dahlgren you're on — a low spot frosts first and a south wall warms early, and one normal is being asked to speak for all 651 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 Dahlgren-wide figureread your own land →
More in Illinois
Wider growing context
What grows across IllinoisDahlgren sits outside our named growing regions, so Illinois as a whole is its closest context here.
Nearby growing guides