Dennison, Minnesota, sits in USDA hardiness zone 4b — enough range to grow cool-season vegetables, hardy fruit, and warm-season crops that mature before the first hard frost.
Reliable performers under these conditions include cabbage, cranberry, turkish rocket, and collard greens; what your own ground favors still comes down to its soil, sun, and drainage.
Even in Dennison, 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 Dennison 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 Dennison — soil, climate, flood, and parcel records. How we handle your address.
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Dennison — the short answer
Dennison, Minnesota: USDA zone 4b, about 179 days between hard freezes, across 803 acres of city.
- USDA zone
- 4b
- USDA PHZM 2023
- Last hard freeze (28°F)
- Apr 21
- NOAA 1991–2020 Climate Normals, 28°F — this town
- First hard freeze (28°F)
- Oct 17
- NOAA 1991–2020 Climate Normals, 28°F — this town
- Days between freezes
- ~179
- NOAA 1991–2020 Climate Normals, 28°F — this town
- City area
- 803 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 4b is Dennison's average, not your lot's — a low corner or a tree line moves it. Against Dennison's 179-day season, see what your own ground reads.
Soil varies lot by lot — soil types explained.
What this means for growing in Dennison
Each reading below is measured for Dennison itself — here is what it means for a garden here, and the move an experienced grower makes about it.
Season length
MeasuredDennison runs about 179 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
MeasuredDennison sits in USDA hardiness zone 4b.
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 Dennison is in
Dennison sits in the Western Corn Belt Plains — EPA Level III, inside the wider Great Plains. That is read at Dennison's own centroid, and it is not what its county reads: Goodhue County is mostly Driftless Area. The wider page above you is answering a different question about different ground.
What Grows in Dennison
Every plant below cleared Dennison's own zone 4b and its 179-day season. Each card opens that plant's Minnesota profile. How we score.
Is it too late to plant in Dennison?
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 24; tender transplants wait until two to three weeks after the last 28°F hard freeze, which lands near Apr 21 (NOAA 1991–2020 climate normals); and from midsummer, planting counts back from the first fall freeze around Oct 17 — long-season crops need about 90 days of runway, quick greens only 30. Even past midsummer there is room for a true fall garden here, and garlic planted near the close carries the momentum into next year.
What's on the federal record near Dennison
Closest first, within ~10 miles of Dennison. Listing isn't leaking, and distance isn't exposure.
- 474688Nitrate · 1300 ft
- 219002Nitrate · 0.9 mi
- Gladys StenhaugUnderground Storage Tanks · 1.4 mi
- Dennison Depot Conv StoreUnderground Storage Tanks · 1.4 mi
- DANIEL PATEBrownfields · 1.5 mi
- GILLISPIE SCRAPBrownfields · 1.6 mi
- 432876Nitrate · 2.7 mi
- 156928Nitrate · 2.9 mi
- HOLDEN FARMS INC - SPRING HILL FACILITYCAFO · 3.5 mi
- JON KELLER FARMCAFO · 3.6 mi
- SUSTANE COMPOST FACILITYCAFO · 3.6 mi
- HOLDEN FARMS INC - PINE GROVE FACILITYCAFO · 3.7 mi
6 more sites are on the record inside the same radius. See them on the map
Measured from Dennison'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 Dennison.
Total Sites
346
within ~10 miles of Dennison
Risk Level
Elevated
Highest-severity
1 Superfund site (none NPL-listed)
Sources Checked
within ~10 miles of Dennison
Severity Distribution
within ~10 miles of Dennison
Highest-Severity Sites
A note from Gnorman
What an experienced grower watches for around here
In and around Dennison, two things run higher than the national average within ~10 miles of Dennison — CAFO (16 sites) and Nitrate (106 sites). It's not cause for alarm — it's worth knowing, and there's a sensible way to grow around it.
CAFO: CAFOs pose a different contamination profile than chemical sources.
Nitrate: Nitrate contamination primarily comes from agricultural fertilizer runoff and failing septic systems.
Wash all produce consumed raw thoroughly, especially leafy greens grown near CAFOs.
Test well water for nitrate if you rely on a private well for irrigation (EPA standard: 10 mg/L).
Check your specific parcel in Dennison
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 Dennison average
Your land is one point inside Dennison
Everything above resolves to Dennison as a whole — one PHZM band and one 28°F frost record, read across 803 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 city 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 Dennison Average
Dennison Average
- ●USDA Zones 4b, averaged across Dennison
- ●One soil character for all of Dennison
- ●Frost dates read at Dennison's scale: Apr 21 to Oct 17
YOUR Parcel
- ✓Your exact zone, not Dennison's 4b
- ✓Your SSURGO soil type & pH
- ✓Your sun exposure, cast in 3D
See MY Growing Report
Read your specific parcel in Dennison
Pull a site-specific report for your exact address in Dennison, Minnesota — soil, sun, drainage, frost risk, and scored plant recommendations.
Three things about your lot that Dennison averages can't show:
We read public map data around Dennison — soil, climate, flood, and parcel records. How we handle your address.
25+ data sources read at your address, not the Dennison average
How we know this about Dennison
The datasets: hardiness from the USDA ARS Plant Hardiness Zone Map 2023, read at this city’s own centroid; hard-freeze dates from NOAA 1991–2020 28°F normals at Dennison’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 city grain anywhere on this page — there is no city-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 Dennison
When does frost risk typically end in Dennison?
The last hard freeze (28°F) in Dennison typically lands around Apr 21, 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 12.
When is the first frost in Dennison?
The first hard freeze (28°F) in Dennison typically arrives around Oct 17, per NOAA 1991–2020 climate normals — the point tender summer crops finish. Lighter frosts run ahead of it, near Oct 3, so the watching starts about Sep 17 — about 179 days after the spring freeze cleared.
How long is the growing season in Dennison?
Measured between 28°F hard freezes, Dennison sees about 179 frost-free days — roughly Apr 21 through Oct 17, per NOAA 1991–2020 climate normals. Tender crops work a shorter one: nearer May 12 to Oct 3, about 144 days.
Is the soil safe to grow vegetables in Dennison?
The federal record around Dennison is a meaningful one — 346 documented sites, mostly Brownfields entries (150), the nearest Nitrate record about 0.2 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.
How do I protect my plants from frost in Dennison?
From about Sep 17 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 17 (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 17. Hardy greens and roots shrug off light frost and sweeten after it — leave them in.
Everything above is measured at Dennison's scale — its 4b band and its 179-day season. Your yard writes its own version of Dennison'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 Dennison’s own scale
6 of the readings below were taken at Dennison's own scale — its own ~179-day season between 28°F freezes, the 803 acres it covers and 346 documented sites around it; 4 are borrowed from a wider read, named and linked below.
Measured here
- Dennison's own USDA hardiness band, zones 4bUSDA PHZM 2023
- Dennison's own 28°F hard-freeze dates, about Apr 21 and Oct 17 and the ~179-day span between themNOAA 1991–2020 Climate Normals
- 346 documented contamination sites on the federal record near Dennison, the closest Nitrate record about 0.2 miles out from the town centreFederal environmental registers
- Dennison's boundary and the 803 acres inside itUS Census TIGER/Line 2025
- Which of 1,086 plants clear zones 4b and a ~179-day seasonGrowable Ground crop-matching engine
- Dennison sits in the Western Corn Belt Plains — not the ecoregion its county mostly readsUS EPA Level III Ecoregions
Inherited from a wider read
- Soil character — no town-scale survey exists, so Dennison's 803 acres read through its county's SSURGO summaryfrom Goodhue County
- Growing-degree days and winter chill — measured county-wide only, so the county page carries themfrom Goodhue County
- The growing challenges every Minnesota grower plans around — written at state scale, so they stay on the state guidefrom Minnesota
- Butterfly and beetle records, and the farmland pesticide estimate — all published county-widefrom Goodhue County
What this page can’t tell you
- The soil pH, drainage, sun hours, and frost pockets on any one lot among Dennison's 803 acreswhy one lot differs from the next →
- Which side of Dennison you're on — a low spot frosts first and a south wall warms early, and one normal is being asked to speak for all 803 acresreading your own microclimate →
- How close that record sits to YOUR lot — the closest Nitrate record about 0.2 miles 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 Dennison-wide figureread your own land →
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