St. Mary, Montana, sits in USDA hardiness zone 4b — a band that supports both cool-season staples and warm-season crops chosen to fit the local frost window.
Crops well matched to these conditions include cabbage, cranberry, cilantro, and collard greens — though what thrives on any one site still turns on its specific soil, sun, and drainage.
Even in St. Mary, 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. Mary 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. Mary — soil, climate, flood, and parcel records. How we handle your address.
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St. Mary — the short answer
St. Mary, Montana: USDA zone 4b, about 132 days between hard freezes, across 482 acres of town.
- USDA zone
- 4b
- USDA PHZM 2023
- Last hard freeze (28°F)
- May 16
- NOAA 1991–2020 Climate Normals, 28°F — this town
- First hard freeze (28°F)
- Sep 25
- NOAA 1991–2020 Climate Normals, 28°F — this town
- Days between freezes
- ~132
- NOAA 1991–2020 Climate Normals, 28°F — this town
- Town area
- 482 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 St. Mary's average, not your lot's — a low corner or a tree line moves it. Against St. Mary's 132-day season, see what your own ground reads.
Soil varies lot by lot — soil types explained.
What this means for growing in St. Mary
Each reading below is measured for St. Mary itself — here is what it means for a garden here, and the move an experienced grower makes about it.
Season length
MeasuredSt. Mary runs about 132 days between hard freezes — a short growing season.
Long-maturing crops like melons, sweet potatoes, and winter squash can run out of runway before the first hard freeze, ripening late or not at all.
Lead with fast-maturing varieties, and stretch the season on both ends with cold frames, low tunnels, or a greenhouse.
NOAA 1991–2020 Climate Normals
Winter hardiness
MeasuredSt. Mary 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. Mary is in
St. Mary sits in the Canadian Rockies — EPA Level III, inside the wider Northwestern Forested Mountains. That is read at St. Mary's own centroid, and it is not what its county reads: Glacier County is mostly Northwestern Glaciated Plains. The wider page above you is answering a different question about different ground.
What Grows in St. Mary
Every plant below cleared St. Mary's own zone 4b and its 132-day season. Each card opens that plant's Montana profile. How we score.
Is it too late to plant in St. Mary?
Almost never — the real question is what to plant next. Cool-season crops can go in from around Apr 18; tender transplants wait until two to three weeks after the last 28°F hard freeze, which lands near May 16 (NOAA 1991–2020 climate normals); and from midsummer, planting counts back from the first fall freeze around Sep 25 — long-season crops need about 90 days of runway, quick greens only 30. Even here the calendar’s edges hold value: thirty-day greens late in the window, then garlic and a rested bed for spring.
What's on the federal record near St. Mary
Closest first, within ~10 miles of St. Mary. Listing isn't leaking, and distance isn't exposure.
- RISING SUN BOAT DOCKUnderground Storage Tanks · 600 ft
- ST MARY LODGEUnderground Storage Tanks · 700 ft
- 35N14W34CCCA01Nitrate · 1100 ft
- 34N14W03BBBA01Nitrate · 1200 ft
- PARK CAFE AND GROCERYUnderground Storage Tanks · 1200 ft
- 35N14W33DADD01Nitrate · 1400 ft
- SAINT MARY RANGER STATIONUnderground Storage Tanks · 1600 ft
- 35N14W33DADC01Nitrate · 1800 ft
- 35N14W33DDBA01Nitrate · 2100 ft
- RISING SUN MOTOR INNUnderground Storage Tanks · 7.5 mi
- ST MARY AUTO SHOPUnderground Storage Tanks · 8.5 mi
- MANY GLACIER HOTEL SERVICE STATIONUnderground Storage Tanks · 8.5 mi
5 more sites are on the record inside the same radius. See them on the map
Measured from St. Mary'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. Mary.
Total Sites
24
within ~10 miles of St. Mary
Risk Level
Low
Highest-severity
1 mining site (prospects, none worked)
Sources Checked
within ~10 miles of St. Mary
Severity Distribution
within ~10 miles of St. Mary
Highest-Severity Sites
Know Before You Grow
- •On a private well, test for nitrates: above 10 mg/L the water needs treatment before irrigating.
- •Underground tanks leak petroleum as they age — near a former filling station, test the soil.
- •Mine waste leaches heavy metals. Test for lead, arsenic and cadmium before growing food here.
Check your specific parcel in St. Mary
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. Mary average
Your land is one point inside St. Mary
Everything above resolves to St. Mary as a whole — one PHZM band and one 28°F frost record, read across 482 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 St. Mary Average
St. Mary Average
- ●USDA Zones 4b, averaged across St. Mary
- ●One soil character for all of St. Mary
- ●Frost dates read at St. Mary's scale: May 16 to Sep 25
YOUR Parcel
- ✓Your exact zone, not St. Mary's 4b
- ✓Your SSURGO soil type & pH
- ✓Your sun exposure, cast in 3D
See MY Growing Report
Read your specific parcel in St. Mary
Pull a site-specific report for your exact address in St. Mary, Montana — soil, sun, drainage, frost risk, and scored plant recommendations.
Three things about your lot that St. Mary averages can't show:
We read public map data around St. Mary — soil, climate, flood, and parcel records. How we handle your address.
25+ data sources read at your address, not the St. Mary average
How we know this about St. Mary
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 St. Mary’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 St. Mary
When does frost risk typically end in St. Mary?
The last hard freeze (28°F) in St. Mary typically lands around May 16, 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 Jun 6.
When is the first frost in St. Mary?
The first hard freeze (28°F) in St. Mary typically arrives around Sep 25, per NOAA 1991–2020 climate normals — the point tender summer crops finish. Lighter frosts run ahead of it, near Sep 11, so the watching starts about Aug 26 — about 132 days after the spring freeze cleared.
How long is the growing season in St. Mary?
Measured between 28°F hard freezes, St. Mary sees about 132 frost-free days — roughly May 16 through Sep 25, per NOAA 1991–2020 climate normals. Tender crops work a shorter one: nearer Jun 6 to Sep 11, about 97 days.
Is the soil safe to grow vegetables in St. Mary?
The federal record around St. Mary is light — 24 documented sites across the 9 federal source types we checked, mostly Nitrate entries (14), the nearest Underground Storage Tanks record about 0.1 miles 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 gardeners stretch the season in St. Mary?
With about 132 frost-free days between hard freezes, St. Mary rewards the classic extension moves: floating row cover buys roughly two to four extra weeks at each shoulder — on this season that is a working window nearer 160 to 188 days — and cold frames or low tunnels buy more. Starting transplants indoors ahead of the May 16 hard-freeze normal stretches the season without touching the calendar.
Everything above is measured at St. Mary's scale — its 4b band and its 132-day season. Your yard writes its own version of St. Mary'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. Mary’s own scale
6 of the readings below were taken at St. Mary's own scale — its own ~132-day season between 28°F freezes, the 482 acres it covers and 24 documented sites around it; 4 are borrowed from a wider read, named and linked below.
Measured here
- St. Mary's own USDA hardiness band, zones 4bUSDA PHZM 2023
- St. Mary's own 28°F hard-freeze dates, about May 16 and Sep 25 and the ~132-day span between themNOAA 1991–2020 Climate Normals
- 24 documented contamination sites on the federal record near St. Mary, the closest Underground Storage Tanks record about 0.1 miles out from the town centreFederal environmental registers
- St. Mary's boundary and the 482 acres inside itUS Census TIGER/Line 2025
- Which of 1,086 plants clear zones 4b and a ~132-day seasonGrowable Ground crop-matching engine
- St. Mary sits in the Canadian Rockies — not the ecoregion its county mostly readsUS EPA Level III Ecoregions
Inherited from a wider read
- Soil character — no town-scale survey exists, so St. Mary's 482 acres read through its county's SSURGO summaryfrom Glacier County
- Growing-degree days and winter chill — measured county-wide only, so the county page carries themfrom Glacier County
- The growing challenges every Montana grower plans around — written at state scale, so they stay on the state guidefrom Montana
- Butterfly and beetle records, and the farmland pesticide estimate — all published county-widefrom Glacier County
What this page can’t tell you
- The soil pH, drainage, sun hours, and frost pockets on any one lot among St. Mary's 482 acreswhy one lot differs from the next →
- Which side of St. Mary you're on — a low spot frosts first and a south wall warms early, and one normal is being asked to speak for all 482 acresreading your own microclimate →
- How close that record sits to YOUR lot — the closest Underground Storage Tanks record about 0.1 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 St. Mary-wide figureread your own land →