Garrison, Montana, sits in USDA hardiness zone 4b — a zone band wide enough that plant choice, not possibility, is the interesting question.
Growers here do well with cabbage, cranberry, cilantro, and collard greens — with the usual caveat that any single yard's soil, sun, and drainage cast the deciding vote.
Even in Garrison, 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 Garrison 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 Garrison — soil, climate, flood, and parcel records. How we handle your address.
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Garrison — the short answer
Garrison, Montana: USDA zone 4b, about 124 days between hard freezes, across 6K acres of town.
- USDA zone
- 4b
- USDA PHZM 2023
- Last hard freeze (28°F)
- May 17
- NOAA 1991–2020 Climate Normals, 28°F — this town
- First hard freeze (28°F)
- Sep 18
- NOAA 1991–2020 Climate Normals, 28°F — this town
- Days between freezes
- ~124
- NOAA 1991–2020 Climate Normals, 28°F — this town
- Town area
- 6K 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 Garrison's average, not your lot's — a low corner or a tree line moves it. Against Garrison's 124-day season, see what your own ground reads.
Soil varies lot by lot — soil types explained.
What this means for growing in Garrison
Each reading below is measured for Garrison itself — here is what it means for a garden here, and the move an experienced grower makes about it.
Season length
MeasuredGarrison runs about 124 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
MeasuredGarrison 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 Garrison is in
Garrison sits in the Middle Rockies — EPA Level III, inside the wider Northwestern Forested Mountains. That is read at Garrison's own centroid rather than borrowed from Powell County.
What Grows in Garrison
Every plant below cleared Garrison's own zone 4b and its 124-day season. Each card opens that plant's Montana profile. How we score.
Is it too late to plant in Garrison?
Usually not — gardeners here simply switch what goes in the ground as the season moves. Cool-season crops can go in from around Apr 19; tender transplants wait until two to three weeks after the last 28°F hard freeze, which lands near May 17 (NOAA 1991–2020 climate normals); and from midsummer, planting counts back from the first fall freeze around Sep 18 — long-season crops need about 90 days of runway, quick greens only 30. Short seasons reward decisiveness — quick-maturing varieties late, hardy greens under cover, and next year’s garlic in the ground before it closes.
What's on the federal record near Garrison
Closest first, within ~10 miles of Garrison. Listing isn't leaking, and distance isn't exposure.
- 09N10W24BBCA01Nitrate · 1.1 mi
- GARRISON MERCANTILE & POST OFFICE INCUnderground Storage Tanks · 1.2 mi
- COMINCO AMERICAN INC USTUnderground Storage Tanks · 1.2 mi
- 09N10W10CDBD01Nitrate · 1.3 mi
- BN GARRISONUnderground Storage Tanks · 1.6 mi
- BN GARRISON MICROWAVEUnderground Storage Tanks · 1.7 mi
- 09N10W04BDBC01Nitrate · 2.9 mi
- 09N09W28CCDD01Nitrate · 4.6 mi
- 10N10W31BABA02Nitrate · 5.2 mi
- 09N09W33CDBC01Nitrate · 5.2 mi
- 10N11W36ACDD01Nitrate · 5.5 mi
- 09N11W01BCAC01Nitrate · 5.6 mi
6 more sites are on the record inside the same radius. See them on the map
Measured from Garrison'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 Garrison.
Total Sites
232
within ~10 miles of Garrison
Risk Level
Elevated
Highest-severity
1 Superfund site (none NPL-listed)
Sources Checked
within ~10 miles of Garrison
Severity Distribution
within ~10 miles of Garrison
Highest-Severity Sites
A note from Gnorman
What an experienced grower watches for around here
In and around Garrison, Nitrate runs higher than the national average — 214 sites within ~10 miles of Garrison. Knowing it is half the work — and it's nothing a thoughtful grower can't plan for.
Nitrate: Nitrate contamination primarily comes from agricultural fertilizer runoff and failing septic systems.
Test well water for nitrate if you rely on a private well for irrigation (EPA standard: 10 mg/L).
Check your specific parcel in Garrison
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 Garrison average
Your land is one point inside Garrison
Everything above resolves to Garrison as a whole — one PHZM band and one 28°F frost record, read across 6K 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 Garrison Average
Garrison Average
- ●USDA Zones 4b, averaged across Garrison
- ●One soil character for all of Garrison
- ●Frost dates read at Garrison's scale: May 17 to Sep 18
YOUR Parcel
- ✓Your exact zone, not Garrison's 4b
- ✓Your SSURGO soil type & pH
- ✓Your sun exposure, cast in 3D
See MY Growing Report
Read your specific parcel in Garrison
Pull a site-specific report for your exact address in Garrison, Montana — soil, sun, drainage, frost risk, and scored plant recommendations.
Three things about your lot that Garrison averages can't show:
We read public map data around Garrison — soil, climate, flood, and parcel records. How we handle your address.
25+ data sources read at your address, not the Garrison average
How we know this about Garrison
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 Garrison’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 Garrison
When does frost risk typically end in Garrison?
The last hard freeze (28°F) in Garrison typically lands around May 17, 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 7.
When is the first frost in Garrison?
The first hard freeze (28°F) in Garrison typically arrives around Sep 18, per NOAA 1991–2020 climate normals — the point tender summer crops finish. Lighter frosts run ahead of it, near Sep 4, so the watching starts about Aug 19 — about 124 days after the spring freeze cleared.
How long is the growing season in Garrison?
Measured between 28°F hard freezes, Garrison sees about 124 frost-free days — roughly May 17 through Sep 18, per NOAA 1991–2020 climate normals. Tender crops work a shorter one: nearer Jun 7 to Sep 4, about 89 days.
Is the soil safe to grow vegetables in Garrison?
The federal record around Garrison is a meaningful one — 232 documented sites, mostly Nitrate entries (214), the nearest Nitrate record about 1.1 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 gardeners stretch the season in Garrison?
With about 124 frost-free days between hard freezes, Garrison 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 152 to 180 days — and cold frames or low tunnels buy more. Starting transplants indoors ahead of the May 17 hard-freeze normal stretches the season without touching the calendar.
Everything above is measured at Garrison's scale — its 4b band and its 124-day season. Your yard writes its own version of Garrison'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 Garrison’s own scale
6 of the readings below were taken at Garrison's own scale — its own ~124-day season between 28°F freezes, the 6,166 acres it covers and 232 documented sites around it; 4 are borrowed from a wider read, named and linked below.
Measured here
- Garrison's own USDA hardiness band, zones 4bUSDA PHZM 2023
- Garrison's own 28°F hard-freeze dates, about May 17 and Sep 18 and the ~124-day span between themNOAA 1991–2020 Climate Normals
- 232 documented contamination sites on the federal record near Garrison, the closest Nitrate record about 1.1 miles out from the town centreFederal environmental registers
- Garrison's boundary and the 6,166 acres inside itUS Census TIGER/Line 2025
- Which of 1,086 plants clear zones 4b and a ~124-day seasonGrowable Ground crop-matching engine
- The ecoregion at Garrison's own centroid, the Middle RockiesUS EPA Level III Ecoregions
Inherited from a wider read
- Soil character — no town-scale survey exists, so Garrison's 6,166 acres read through its county's SSURGO summaryfrom Powell County
- Growing-degree days and winter chill — measured county-wide only, so the county page carries themfrom Powell 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 Powell County
What this page can’t tell you
- The soil pH, drainage, sun hours, and frost pockets on any one lot among Garrison's 6,166 acreswhy one lot differs from the next →
- Which side of Garrison you're on — a low spot frosts first and a south wall warms early, and one normal is being asked to speak for all 6,166 acresreading your own microclimate →
- How close that record sits to YOUR lot — the closest Nitrate record about 1.1 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 Garrison-wide figureread your own land →
More in Montana
Wider growing context
What grows across MontanaGarrison sits outside our named growing regions, so Montana as a whole is its closest context here.
Nearby growing guides