St. Clair, Michigan, sits in USDA hardiness zone 6a — a zone band wide enough that plant choice, not possibility, is the interesting question.
Expect cabbage, hazelnut, lavender, and collard greens to be strong candidates here; the deciding factors on any one parcel stay local — soil, sun, and drainage.
Even in St. Clair, 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 St. Clair 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 St. Clair — soil, climate, flood, and parcel records. How we handle your address.
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St. Clair — the short answer
St. Clair, Michigan: USDA zone 6a, about 204 days between hard freezes, across 2K acres of city.
- USDA zone
- 6a
- USDA PHZM 2023
- Last hard freeze (28°F)
- Apr 15
- NOAA 1991–2020 Climate Normals, 28°F — this town
- First hard freeze (28°F)
- Nov 5
- NOAA 1991–2020 Climate Normals, 28°F — this town
- Days between freezes
- ~204
- NOAA 1991–2020 Climate Normals, 28°F — this town
- City area
- 2K 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 6a is St. Clair's average, not your lot's — a low corner or a tree line moves it. Against St. Clair's 204-day season, see what your own ground reads.
Soil varies lot by lot — soil types explained.
What this means for growing in St. Clair
Each reading below is measured for St. Clair itself — here is what it means for a garden here, and the move an experienced grower makes about it.
Season length
MeasuredSt. Clair runs about 204 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
MeasuredSt. Clair sits in USDA hardiness zone 6a.
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. Clair is in
St. Clair sits in the Huron/Erie Lake Plains — EPA Level III, inside the wider Eastern Temperate Forests. That is read at St. Clair's own centroid rather than borrowed from St. Clair County.
What Grows in St. Clair
Every plant below cleared St. Clair's own zone 6a and its 204-day season. Each card opens that plant's Michigan profile. How we score.
Is it too late to plant in St. Clair?
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 18; tender transplants wait until two to three weeks after the last 28°F hard freeze, which lands near Apr 15 (NOAA 1991–2020 climate normals); and from midsummer, planting counts back from the first fall freeze around Nov 5 — long-season crops need about 90 days of runway, quick greens only 30. With a season this long, “too late” mostly means “switch crops” — second sowings and a full fall garden are the norm, with garlic closing the year.
Documented around St. Clair
Survey cells within 31 miles of St. Clair checked for spotted lanternfly, none carrying a detection — a surveyed negative, not an absence of looking. Nearest documented record 43 miles off. What to watch for.
What's on the federal record near St. Clair
Closest first, within ~10 miles of St. Clair. Listing isn't leaking, and distance isn't exposure.
- Theo V Eddy Elementary SchoolUnderground Storage Tanks · 150 ft
- St Clair CO (M18367)Underground Storage Tanks · 850 ft
- SBC SERVICES INCBrownfields · 850 ft
- PETERNEL ENTERPRISES LLCBrownfields · 1400 ft
- WITHERELL MERCURY SITESuperfund · 1800 ft
- Kelly & Son ServiceUnderground Storage Tanks · 2000 ft
- St Clair Housing ComissionUnderground Storage Tanks · 2000 ft
- St Clair InnUnderground Storage Tanks · 2000 ft
- ST. CLAIR RESIDENTIAL MERCURY SPILLSuperfund · 2000 ft
- Sunrise Store #60Underground Storage Tanks · 2200 ft
- RIVERSIDE TANK & MANUFACTURING CORPBrownfields · 2300 ft
- St Clair Plumbing & Heating IncUnderground Storage Tanks · 2300 ft
6 more sites are on the record inside the same radius. See them on the map
Measured from St. Clair'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. Clair.
Total Sites
427
within ~10 miles of St. Clair
Risk Level
Elevated
Highest-severity
5 Superfund sites (none NPL-listed)
Sources Checked
within ~10 miles of St. Clair
Severity Distribution
within ~10 miles of St. Clair
Highest-Severity Sites
A note from Gnorman
What an experienced grower watches for around here
In and around St. Clair, two things run higher than the national average within ~10 miles of St. Clair — PFAS (9 sites) and Toxics Release Inventory (49 sites). It's not cause for alarm — it's worth knowing, and there's a sensible way to grow around it.
PFAS: PFAS (per- and polyfluoroalkyl substances) are called "forever chemicals" because they do not biodegrade.
Toxics Release Inventory: TRI facilities report annual chemical releases to air, water, and land.
Test irrigation water source — this is the primary pathway for PFAS to reach garden crops.
Check prevailing wind direction — downwind parcels face higher exposure than upwind or crosswind locations.
Check your specific parcel in St. Clair
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. Clair average
Your land is one point inside St. Clair
Everything above resolves to St. Clair as a whole — one PHZM band and one 28°F frost record, read across 2K 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 St. Clair Average
St. Clair Average
- ●USDA Zones 6a, averaged across St. Clair
- ●One soil character for all of St. Clair
- ●Frost dates read at St. Clair's scale: Apr 15 to Nov 5
YOUR Parcel
- ✓Your exact zone, not St. Clair's 6a
- ✓Your SSURGO soil type & pH
- ✓Your sun exposure, cast in 3D
See MY Growing Report
Read your specific parcel in St. Clair
Pull a site-specific report for your exact address in St. Clair, Michigan — soil, sun, drainage, frost risk, and scored plant recommendations.
Three things about your lot that St. Clair averages can't show:
We read public map data around St. Clair — soil, climate, flood, and parcel records. How we handle your address.
25+ data sources read at your address, not the St. Clair average
How we know this about St. Clair
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 St. Clair’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 St. Clair
When does frost risk typically end in St. Clair?
The last hard freeze (28°F) in St. Clair typically lands around Apr 15, 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 6.
When is the first frost in St. Clair?
The first hard freeze (28°F) in St. Clair typically arrives around Nov 5, per NOAA 1991–2020 climate normals — the point tender summer crops finish. Lighter frosts run ahead of it, near Oct 22, so the watching starts about Oct 6 — about 204 days after the spring freeze cleared.
How long is the growing season in St. Clair?
Measured between 28°F hard freezes, St. Clair sees about 204 frost-free days — roughly Apr 15 through Nov 5, per NOAA 1991–2020 climate normals. Tender crops work a shorter one: nearer May 6 to Oct 22, about 169 days.
Is the soil safe to grow vegetables in St. Clair?
The federal record around St. Clair is a meaningful one — 427 documented sites, mostly Brownfields entries (186), the nearest Underground Storage Tanks record under a tenth of a mile 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 St. Clair?
From about Oct 6 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 5 (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 5. Hardy greens and roots shrug off light frost and sweeten after it — leave them in.
Everything above is measured at St. Clair's scale — its 6a band and its 204-day season. Your yard writes its own version of St. Clair'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 St. Clair’s own scale
7 of the readings below were taken at St. Clair's own scale — its own ~204-day season between 28°F freezes, the 1,882 acres it covers and 427 documented sites around it; 4 are borrowed from a wider read, named and linked below.
Measured here
- St. Clair's own USDA hardiness band, zones 6aUSDA PHZM 2023
- St. Clair's own 28°F hard-freeze dates, about Apr 15 and Nov 5 and the ~204-day span between themNOAA 1991–2020 Climate Normals
- 427 documented contamination sites on the federal record near St. Clair, the closest Underground Storage Tanks record under a tenth of a mile out from the town centreFederal environmental registers
- St. Clair's boundary and the 1,882 acres inside itUS Census TIGER/Line 2025
- Which of 1,086 plants clear zones 6a and a ~204-day seasonGrowable Ground crop-matching engine
- The ecoregion at St. Clair's own centroid, the Huron/Erie Lake PlainsUS EPA Level III Ecoregions
- Lanternfly survey cells around St. Clair checked, none carrying a detectionlydemapr (De Bona & Helmus), 10 km survey lattice
Inherited from a wider read
- Soil character — no town-scale survey exists, so St. Clair's 1,882 acres read through its county's SSURGO summaryfrom St. Clair County
- Growing-degree days and winter chill — measured county-wide only, so the county page carries themfrom St. Clair County
- The growing challenges every Michigan grower plans around — written at state scale, so they stay on the state guidefrom Michigan
- Butterfly and beetle records, and the farmland pesticide estimate — all published county-widefrom St. Clair County
What this page can’t tell you
- The soil pH, drainage, sun hours, and frost pockets on any one lot among St. Clair's 1,882 acreswhy one lot differs from the next →
- Which side of St. Clair you're on — a low spot frosts first and a south wall warms early, and one normal is being asked to speak for all 1,882 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 St. Clair-wide figureread your own land →
More in Michigan
Wider growing context
What grows across MichiganSt. Clair sits outside our named growing regions, so Michigan as a whole is its closest context here.
Nearby growing guides