St. Maries, Idaho, sits in USDA hardiness zone 6b — a zone band wide enough that plant choice, not possibility, is the interesting question.
A short list that earns its place here — cabbage, blackberry, california poppy, and collard greens — with any one site's soil, sun, and drainage making the final cut.
Even in St. Maries, 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. Maries 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. Maries — soil, climate, flood, and parcel records. How we handle your address.
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St. Maries — the short answer
St. Maries, Idaho: USDA zone 6b, about 187 days between hard freezes, across 760 acres of city.
- USDA zone
- 6b
- USDA PHZM 2023
- Last hard freeze (28°F)
- Apr 15
- NOAA 1991–2020 Climate Normals, 28°F — this town
- First hard freeze (28°F)
- Oct 19
- NOAA 1991–2020 Climate Normals, 28°F — this town
- Days between freezes
- ~187
- NOAA 1991–2020 Climate Normals, 28°F — this town
- City area
- 760 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 St. Maries's average, not your lot's — a low corner or a tree line moves it. Against St. Maries's 187-day season, see what your own ground reads.
Soil varies lot by lot — soil types explained.
What this means for growing in St. Maries
Each reading below is measured for St. Maries itself — here is what it means for a garden here, and the move an experienced grower makes about it.
Season length
MeasuredSt. Maries runs about 187 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. Maries 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 St. Maries is in
St. Maries sits in the Northern Rockies — EPA Level III, inside the wider Northwestern Forested Mountains. That is read at St. Maries's own centroid rather than borrowed from Benewah County.
What Grows in St. Maries
Every plant below cleared St. Maries's own zone 6b and its 187-day season. Each card opens that plant's Idaho profile. How we score.
Is it too late to plant in St. Maries?
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 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 Oct 19 — 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 St. Maries
Closest first, within ~10 miles of St. Maries. Listing isn't leaking, and distance isn't exposure.
- St. Maries Joint School District No. 41 Bus GarageUnderground Storage Tanks · 350 ft
- VACANT LOTUnderground Storage Tanks · 750 ft
- KEN'S BODY SHOPUnderground Storage Tanks · 750 ft
- GERALD HAASUnderground Storage Tanks · 1200 ft
- 10th Street SuperstopUnderground Storage Tanks · 1200 ft
- BENEWAH COMMUNITY HOSPITALUnderground Storage Tanks · 1400 ft
- CITY OF ST. MARIESUnderground Storage Tanks · 1600 ft
- PENDELL OIL INCUnderground Storage Tanks · 1800 ft
- ST. MARIES GENERATOR (1340-BO2)Underground Storage Tanks · 1900 ft
- Potlatch CorporationUnderground Storage Tanks · 1900 ft
- IDL-ST. MARIESUnderground Storage Tanks · 2000 ft
- THIRD STREET ONE STOPUnderground Storage Tanks · 2000 ft
6 more sites are on the record inside the same radius. See them on the map
Measured from St. Maries'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. Maries.
Sources Checked
within ~10 miles of St. Maries
Severity Distribution
within ~10 miles of St. Maries
Highest-Severity Sites
A note from Gnorman
What an experienced grower watches for around here
In and around St. Maries, two things run higher than the national average within ~10 miles of St. Maries — Mining (10 sites) and Nitrate (44 sites). Knowing it is half the work — and it's nothing a thoughtful grower can't plan for.
Mining: Mining sites — both historic and active — can leach heavy metals (arsenic, lead, cadmium, mercury) into soil and water for centuries after operations cease.
Nitrate: Nitrate contamination primarily comes from agricultural fertilizer runoff and failing septic systems.
Test soil for heavy metals (lead, arsenic, cadmium, mercury) — this is essential near any mining site.
Test well water for nitrate if you rely on a private well for irrigation (EPA standard: 10 mg/L).
Check your specific parcel in St. Maries
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. Maries average
Your land is one point inside St. Maries
Everything above resolves to St. Maries as a whole — one PHZM band and one 28°F frost record, read across 760 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. Maries Average
St. Maries Average
- ●USDA Zones 6b, averaged across St. Maries
- ●One soil character for all of St. Maries
- ●Frost dates read at St. Maries's scale: Apr 15 to Oct 19
YOUR Parcel
- ✓Your exact zone, not St. Maries's 6b
- ✓Your SSURGO soil type & pH
- ✓Your sun exposure, cast in 3D
See MY Growing Report
Read your specific parcel in St. Maries
Pull a site-specific report for your exact address in St. Maries, Idaho — soil, sun, drainage, frost risk, and scored plant recommendations.
Three things about your lot that St. Maries averages can't show:
We read public map data around St. Maries — soil, climate, flood, and parcel records. How we handle your address.
25+ data sources read at your address, not the St. Maries average
How we know this about St. Maries
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. Maries’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. Maries
When does frost risk typically end in St. Maries?
The last hard freeze (28°F) in St. Maries 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. Maries?
The first hard freeze (28°F) in St. Maries typically arrives around Oct 19, per NOAA 1991–2020 climate normals — the point tender summer crops finish. Lighter frosts run ahead of it, near Oct 5, so the watching starts about Sep 19 — about 187 days after the spring freeze cleared.
How long is the growing season in St. Maries?
Measured between 28°F hard freezes, St. Maries sees about 187 frost-free days — roughly Apr 15 through Oct 19, per NOAA 1991–2020 climate normals. Tender crops work a shorter one: nearer May 6 to Oct 5, about 152 days.
Is the soil safe to grow vegetables in St. Maries?
The federal record around St. Maries is a meaningful one — 89 documented sites, mostly Nitrate entries (44), 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. Maries?
From about Sep 19 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 19 (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 19. Hardy greens and roots shrug off light frost and sweeten after it — leave them in.
Everything above is measured at St. Maries's scale — its 6b band and its 187-day season. Your yard writes its own version of St. Maries'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. Maries’s own scale
6 of the readings below were taken at St. Maries's own scale — its own ~187-day season between 28°F freezes, the 760 acres it covers and 89 documented sites around it; 4 are borrowed from a wider read, named and linked below.
Measured here
- St. Maries's own USDA hardiness band, zones 6bUSDA PHZM 2023
- St. Maries's own 28°F hard-freeze dates, about Apr 15 and Oct 19 and the ~187-day span between themNOAA 1991–2020 Climate Normals
- 89 documented contamination sites on the federal record near St. Maries, the closest Underground Storage Tanks record under a tenth of a mile out from the town centreFederal environmental registers
- St. Maries's boundary and the 760 acres inside itUS Census TIGER/Line 2025
- Which of 1,086 plants clear zones 6b and a ~187-day seasonGrowable Ground crop-matching engine
- The ecoregion at St. Maries's own centroid, the Northern RockiesUS EPA Level III Ecoregions
Inherited from a wider read
- Soil character — no town-scale survey exists, so St. Maries's 760 acres read through its county's SSURGO summaryfrom Benewah County
- Growing-degree days and winter chill — measured county-wide only, so the county page carries themfrom Benewah County
- The growing challenges every Idaho grower plans around — written at state scale, so they stay on the state guidefrom Idaho
- Butterfly and beetle records, and the farmland pesticide estimate — all published county-widefrom Benewah County
What this page can’t tell you
- The soil pH, drainage, sun hours, and frost pockets on any one lot among St. Maries's 760 acreswhy one lot differs from the next →
- Which side of St. Maries you're on — a low spot frosts first and a south wall warms early, and one normal is being asked to speak for all 760 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. Maries-wide figureread your own land →
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