St. Mary's, Alaska, 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.
Expect cabbage, chokecherry, roman chamomile, and collard greens to be strong candidates here; the deciding factors on any one parcel stay local — soil, sun, and drainage.
Even in St. Mary's, 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's 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's — soil, climate, flood, and parcel records. How we handle your address.
No card required · your full report in seconds
St. Mary's — the short answer
St. Mary's, Alaska: USDA zone 4b, across 29K acres of city.
- USDA zone
- 4b
- USDA PHZM 2023
- Last hard freeze (statewide)
- Apr 16 - May 15
- NOAA RCC ACIS 1991–2020, state middle half
- First hard freeze (statewide)
- Sep 24 - Oct 29
- NOAA RCC ACIS 1991–2020, state middle half
- City area
- 29K acres
- US Census TIGER/Line 2025
Every figure names the dataset it came from. Where no local normal resolves, the figure is the statewide middle-half window, labelled as such rather than passed off as local.
Hardiness Zone Range
Growing Season
Zone 4b is St. Mary's's average, not your lot's — a low corner or a tree line moves it. Against that, see what your own ground reads.
Soil varies lot by lot — soil types explained.
What this means for growing in St. Mary's
Each reading below is measured for St. Mary's itself — here is what it means for a garden here, and the move an experienced grower makes about it.
Winter hardiness
MeasuredSt. Mary's 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
What Grows in St. Mary's
Every plant below cleared St. Mary's's own zone 4b. Each card opens that plant's Alaska profile. How we score.
What's on the federal record near St. Mary's
Closest first, within ~10 miles of St. Mary's. Listing isn't leaking, and distance isn't exposure.
- USDOT FAA SAINT MARYS AIR NAV STASuperfund · 1.3 mi
- ADOTPF - Saint MarysUnderground Storage Tanks · 1.5 mi
- ST Mary's AirportUnderground Storage Tanks · 1.5 mi
- DOT&PF SAINT MARYS AIRPORTBrownfields · 1.7 mi
Measured from St. Mary's'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's.
Total Sites
4
within ~10 miles of St. Mary's
Risk Level
Elevated
Highest-severity
1 Superfund site (none NPL-listed)
Severity Distribution
within ~10 miles of St. Mary's
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.
- •A Superfund listing means federally documented contamination. Test soil and water before planting edibles nearby.
Check your specific parcel in St. Mary's
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's average
Your land is one point inside St. Mary's
Everything above resolves to St. Mary's as a whole — one PHZM band and one 28°F frost record, read across 29K 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. Mary's Average
St. Mary's Average
- ●USDA Zones 4b, averaged across St. Mary's
- ●One soil character for all of St. Mary's
- ●State-average frost dates
YOUR Parcel
- ✓Your exact zone, not St. Mary's's 4b
- ✓Your SSURGO soil type & pH
- ✓Your sun exposure, cast in 3D
See MY Growing Report
Read your specific parcel in St. Mary's
Pull a site-specific report for your exact address in St. Mary's, Alaska — soil, sun, drainage, frost risk, and scored plant recommendations.
Three things about your lot that St. Mary's averages can't show:
We read public map data around St. Mary's — soil, climate, flood, and parcel records. How we handle your address.
25+ data sources read at your address, not the St. Mary's average
How we know this about St. Mary's
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, with the labelled statewide window where none resolves; 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. Mary's
When does frost risk typically end in St. Mary's?
St. Mary's has no hard-freeze normal of its own, so it follows Alaska's statewide window: the middle half of counties see their last spring hard freeze (28°F) around Apr 16 - May 15 and their first fall hard freeze around Sep 24 - Oct 29, per NOAA Regional Climate Centers ACIS (1991–2020). Frost dates shift with elevation and local microclimate, so watch your own site's cold pockets. That marks the hard freeze, not the last light frost — light frosts can still bite for a few more weeks, so tender transplants usually wait another 2–3 weeks.
Is the soil safe to grow vegetables in St. Mary's?
The federal record around St. Mary's is a meaningful one — 4 documented sites, mostly Underground Storage Tanks entries (2), the nearest Superfund record about 1.3 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 St. Mary's?
As the season closes around Alaska's statewide first fall hard freeze (28°F) near Sep 24 - Oct 29 (NOAA Regional Climate Centers ACIS (1991–2020)), 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 the first hard night. Hardy greens and roots shrug off light frost and sweeten after it — leave them in.
Everything above is measured at St. Mary's's scale — its 4b band and its zone 4b. Your yard writes its own version of St. Mary's'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’s own scale
4 of the readings below were taken at St. Mary's's own scale — the 28,547 acres it covers and 4 documented sites around it; 5 are borrowed from a wider read, named and linked below.
Measured here
- St. Mary's's own USDA hardiness band, zones 4bUSDA PHZM 2023
- 4 documented contamination sites on the federal record near St. Mary's, the closest Superfund record about 1.3 miles out from the town centreFederal environmental registers
- St. Mary's's boundary and the 28,547 acres inside itUS Census TIGER/Line 2025
- Which of 1,086 plants clear St. Mary's's hardiness zoneGrowable Ground crop-matching engine
Inherited from a wider read
- The frost window — no local hard-freeze normal resolved here, so the statewide dates stand infrom Alaska
- Soil character — no town-scale survey exists, so St. Mary's's 28,547 acres read through its county's SSURGO summaryfrom Kusilvak County
- Growing-degree days and winter chill — measured county-wide only, so the county page carries themfrom Kusilvak County
- The growing challenges every Alaska grower plans around — written at state scale, so they stay on the state guidefrom Alaska
- Butterfly and beetle records, and the farmland pesticide estimate — all published county-widefrom Kusilvak 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's 28,547 acreswhy one lot differs from the next →
- Which side of St. Mary's you're on — a low spot frosts first and a south wall warms early, and one normal is being asked to speak for all 28,547 acresreading your own microclimate →
- How close that record sits to YOUR lot — the closest Superfund record about 1.3 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's-wide figureread your own land →
More in Alaska
Wider growing context
What grows across AlaskaSt. Mary's sits outside our named growing regions, so Alaska as a whole is its closest context here.
Nearby growing guides