St. Croix County, in Wisconsin, sits in USDA hardiness zone 4b — a range where zone-matched perennials and frost-aware annual timing set what succeeds.
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.
Grounded in USDA PHZM 2023 · Growable Ground suitability scoring · NOAA 1991–2020 Climate Normals
St. Croix County holds more than one microclimate.
Soils and elevations shift across St. Croix 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 St. Croix County — soil, climate, flood, and parcel records. How we handle your address.
No card required · your full report in seconds
St. Croix County — the short answer
St. Croix County, Wisconsin: USDA zone 4b, about 175 days between hard freezes, across 462K acres.
- USDA zone
- 4b
- USDA PHZM 2023
- Last hard freeze (28°F)
- Apr 24
- NOAA 1991–2020 Climate Normals, 28°F
- First hard freeze (28°F)
- Oct 16
- NOAA 1991–2020 Climate Normals, 28°F
- Days between freezes
- ~175
- NOAA 1991–2020 Climate Normals, 28°F
- County area
- 462K 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 4b is St. Croix County's average, not your lot's — a low corner or a tree line moves it. Against St. Croix County's 175-day season, see what your own ground reads.
Heat in St. Croix County
Across a year, St. Croix County accumulates about 2,136 growing degree days above 50°F, about 14 fewer than the middle Wisconsin county — ahead of 33 of Wisconsin’s 72 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 St. Croix County
Across St. Croix County, the ground is predominantly Alfisols, where Santiago, Sattre, and Amery are the most extensive named soil series. The soil is generally well drained with a silt loam surface. Topsoil pH runs about 5.9–6.2, moderately acidic. Rainfall drains through hydrologic group B soils.
Soil order
Alfisols
Drainage
Well drained
Prime farmland
45%
Hydric soils
5%
Soil still varies lot by lot — soil types explained.
How the ground varies across St. Croix County
The USDA soil survey maps 53% of St. Croix County as well drained — but another 44% drains differently: 15% moderately well drained, 13% somewhat poorly drained.
Santiago is the most extensive named soil at 11% of mapped acres, then Sattre (10%) and Amery (7%).
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 St. Croix County
Each reading below is measured for St. Croix 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 St. Croix 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 St. Croix County runs about pH 5.9–6.2, 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
Season length
MeasuredSt. Croix County runs about 175 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
MeasuredSt. Croix County 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 St. Croix County is in
St. Croix County spans 3 EPA Level III ecoregions — Western Corn Belt Plains (52%), North Central Hardwood Forests (42%) and Driftless Area (6%). 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 St. Croix County
We scored all 1,086 plants against St. Croix County's own USDA zone 4b and its own 175-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 Wisconsin profile.
Is it too late to plant in St. Croix County?
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 27; tender transplants wait until two to three weeks after the last 28°F hard freeze, which lands near Apr 24 (NOAA 1991–2020 climate normals); and from midsummer, planting counts back from the first fall freeze around Oct 16 — long-season crops need about 90 days of runway, quick greens only 30. As the window narrows, the plantings just get faster — fall brassicas, then greens, then garlic to finish.
Documented around St. Croix County
- Japanese beetle1 documented records
- monarch butterfly66 documented records
Sighting records, so they follow observers as much as insects.
What gets applied to farmland in St. Croix County
USGS estimates 136,522 lb of Glyphosate on St. Croix County farmland in 2019, its largest by weight, ahead of Metolachlor & Metolachlor-s (98,173 lb) and Metolachlor-s (86,734 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 St. Croix County — and how to grow with it.
We checked the federal record across St. Croix County — 957 documented sites across 7 of the 9 source types we track.
The most significant on record: 7 Superfund sites (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 St. Croix 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 St. Croix County
Closest first, across St. Croix County. Listing isn't leaking, and distance isn't exposure.
- SC-29/17W/03-0404Nitrate · 0.6 mi
- Donald SershenUnderground Storage Tanks · 1.8 mi
- STUCKEYSUnderground Storage Tanks · 1.8 mi
- Hubert NeumanUnderground Storage Tanks · 1.8 mi
- DOUGLAS HANSON CO INCUnderground Storage Tanks · 1.8 mi
- ROLLING HILLS FARMUnderground Storage Tanks · 1.8 mi
- SC-30/17W/29-0751Nitrate · 2.6 mi
- Ken Rich Farm IncUnderground Storage Tanks · 2.6 mi
- LINDQUIST REPAIRBrownfields · 3.2 mi
- HAMMOND HEALTH SERVICESBrownfields · 3.3 mi
- SC-30/17W/30-0088Nitrate · 3.3 mi
- Holiday #53Underground Storage Tanks · 3.4 mi
6 more sites are on the record inside the same radius. See them on the map
Measured from St. Croix 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 St. Croix County.
Total Sites
957
across St. Croix County
Risk Level
Elevated
Highest-severity
7 Superfund sites (none NPL-listed)
Sources Checked
across St. Croix County
Severity Distribution
across St. Croix County
Highest-Severity Sites
Know Before You Grow
- •Underground tanks leak petroleum as they age — near a former filling station, test the soil.
- •Near a brownfield, raised beds of imported soil give your food clean ground.
- •On a private well, test for nitrates: above 10 mg/L the water needs treatment before irrigating.
Check your specific parcel in St. Croix 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 St. Croix County average
Your land is one point inside St. Croix County
Everything above resolves to St. Croix County as a whole — one PHZM band and one county frost record, read across 462K 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 St. Croix County Average
St. Croix County Average
- ●USDA Zones 4b, averaged across St. Croix County
- ●One soil character for all of St. Croix County
- ●Frost dates read at St. Croix County's scale: Apr 24 to Oct 16
YOUR Parcel
- ✓Your exact zone, not St. Croix County's 4b
- ✓Your SSURGO soil type & pH
- ✓Your sun exposure, cast in 3D
See MY Growing Report
Read your parcel in St. Croix County
Pull a site-specific report for your exact address in St. Croix County, Wisconsin — soil, sun, drainage, frost risk, and scored plant recommendations.
Three things about your lot that St. Croix County averages can't show:
We read public map data around St. Croix County — soil, climate, flood, and parcel records. How we handle your address.
25+ data sources read at your address, not the St. Croix County average
How we know this about St. Croix 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 St. Croix County carries no record of its own, the figure is inherited and labelled — the resolution ledger below names each.
Common questions about St. Croix County
When does frost risk typically end in St. Croix County?
The last hard freeze (28°F) in St. Croix County typically lands around Apr 24, 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 15.
How long is the growing season in St. Croix County?
Measured between 28°F hard freezes, St. Croix County sees about 175 frost-free days — roughly Apr 24 through Oct 16, per NOAA 1991–2020 climate normals. Tender crops work a shorter one: nearer May 15 to Oct 2, about 140 days.
Is the soil safe to grow vegetables in St. Croix County?
The federal record around St. Croix County is a meaningful one — 957 documented sites, mostly Underground Storage Tanks entries (350), the nearest Nitrate record about 0.6 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 St. Croix County's scale — its 4b band and its 175-day season. Your yard writes its own version of St. Croix 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 Wisconsin's frost window, season length, and soil profile against the plant's real requirements.
What this page reads at St. Croix County’s own scale
9 of the readings below were taken at St. Croix County's own scale — its own ~175-day span between 28°F freezes, the 3 most extensive soil series mapped here and 957 documented sites inside its boundary; one is borrowed from a wider read, named and linked below.
Measured here
- St. Croix County's own USDA hardiness band, zones 4bUSDA PHZM 2023
- St. Croix County's own 28°F hard-freeze dates and its ~175-day span between themNOAA 1991–2020 Climate Normals
- The soil order, drainage, surface pH, and the 3 most extensive named soil series mapped in St. Croix CountyUSDA NRCS SSURGO
- 957 documented contamination sites inside the county boundary, distance-sorted from its center — the closest Nitrate record about 0.6 miles outFederal environmental registers
- St. Croix County's boundary and the 462,181 acres inside itUS Census TIGER/Line 2025
- Which of 1,086 plants clear zones 4b and a ~175-day seasonGrowable Ground crop-matching engine
- The 3 ecoregions St. Croix County spans, Western Corn Belt Plains the largestUS EPA Level III Ecoregions
- Open occurrence records documented in St. Croix County for 2 tracked speciesGBIF derived datasets (CC0 / CC BY 4.0)
- Which agricultural compounds go onto St. Croix County farmland, and roughly how muchUSGS NAWQA EPest county estimates
Inherited from a wider read
- The growing challenges every Wisconsin grower plans around — written at state scale, so they stay on the state guidefrom Wisconsin
What this page can’t tell you
- How the season shifts across St. Croix County — the ~175 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 St. Croix County's 462,181 acreswhy one lot differs from the next →
- Which of those 957 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 St. Croix Countyread your own land →