Granite County, in Montana, sits in USDA hardiness zone 5a — a range where zone-matched perennials and frost-aware annual timing set what succeeds.
Crops well matched to these conditions include okra, cranberry, lavender, and pumpkin — though what thrives on any one site still turns on its specific soil, sun, and drainage.
Grounded in USDA PHZM 2023 · Growable Ground suitability scoring · NOAA 1991–2020 Climate Normals
Granite County holds more than one microclimate.
Soils and elevations shift across Granite County, so your frost dates and drainage aren't the county average. 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 Granite County — soil, climate, flood, and parcel records. How we handle your address.
No card required · your full report in seconds
Granite County — the short answer
Granite County, Montana: USDA zone 5a, about 118 days between hard freezes, across 1.1M acres.
- USDA zone
- 5a
- USDA PHZM 2023
- Last hard freeze (28°F)
- May 28
- NOAA 1991–2020 Climate Normals, 28°F
- First hard freeze (28°F)
- Sep 23
- NOAA 1991–2020 Climate Normals, 28°F
- Days between freezes
- ~118
- NOAA 1991–2020 Climate Normals, 28°F
- County area
- 1.1M acres
- US Census TIGER/Line 2025
Every figure names the dataset it came from. Hard-freeze dates are county 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 5a is Granite County's average, not your lot's — a low corner or a tree line moves it. Against Granite County's 118-day season, see what your own ground reads.
Heat in Granite County
Across a year, Granite County accumulates about 647 growing degree days above 50°F, about 1,023 fewer than the middle Montana county — ahead of 2 of Montana’s 56 counties. Degree days are the heat a crop actually gets to work with — more of them is more room to ripen a long-season crop before the freeze closes the window.
Grounded in PRISM Climate Group, Oregon State University — 1991–2020 monthly normals
Soil in Granite County
Across Granite County, the ground is predominantly Inceptisols, where Whitecow, Danvers, and Braziel are the most extensive named soil series. The soil is generally well drained with a gravelly loam surface. Topsoil pH runs about 6.0–6.7, slightly acidic. Rainfall drains through hydrologic group B soils.
Soil order
Inceptisols
Drainage
Well drained
Prime farmland
2%
Hydric soils
2%
Soil still varies lot by lot — soil types explained.
How the ground varies across Granite County
The USDA soil survey maps 73% of Granite County as well drained — but another 23% drains differently: 16% somewhat excessively drained, 4% excessively drained.
Whitecow is the most extensive named soil at 2% of mapped acres, then Danvers (1%) and Braziel (1%).
Which of them your own lot sits on is a parcel question, not a county one. Check your address for the survey at your boundary.
What this means for growing in Granite County
Each reading below is measured for Granite County itself — here is what it means for a garden here, and the move an experienced grower makes about it.
Drainage
MeasuredThe dominant soils across Granite County are well drained, in hydrologic group B — ground that drains quickly.
The upside is soil you can work early in spring and roots that never drown; the cost is that fast-draining ground dries out fast and leaches nutrients away before plants can use them.
Work in compost and mulch to hold moisture and feed, and water more often in short doses than deep and rarely.
USDA NRCS SSURGO
Surface pH
MeasuredTopsoil across Granite County runs about pH 6.0–6.7, close to neutral.
This is the range most vegetables prefer — one correction you probably do not have to make, which is genuinely good news for a new bed.
Keep it there with compost rather than lime or sulfur, and only amend if your own soil test says otherwise.
USDA NRCS SSURGO
Season length
MeasuredGranite County runs about 118 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
MeasuredGranite County sits in USDA hardiness zone 5a.
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 Granite County is in
Granite County sits in the Middle Rockies — EPA Level III, inside the wider Northwestern Forested Mountains. One consistent ecological setting across the whole county.
What Grows in Granite County
We scored all 1,086 plants against Granite County's own USDA zone 5a and its own 118-day season between hard freezes, using the same matching engine that runs a full parcel report. These cleared both. Sun, soil pH and drainage vary lot by lot — those are the parcel questions below. Each card opens that plant's Montana profile.
Is it too late to plant in Granite County?
For most of the year, no — what changes is which crops still fit the days remaining. Cool-season crops can go in from around Apr 30; tender transplants wait until two to three weeks after the last 28°F hard freeze, which lands near May 28 (NOAA 1991–2020 climate normals); and from midsummer, planting counts back from the first fall freeze around Sep 23 — 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 gets applied to farmland in Granite County
USGS estimates 11,203 lb of Glyphosate on Granite County farmland in 2019, its largest by weight, ahead of 2,4-d (5,885 lb) and Atrazine (3,107 lb).
Farmland across the whole county, not any one lot. Check your address for the site-by-site record.
Safe to Grow Here?
What the federal record shows across Granite County — and how to grow with it.
We checked the federal record across Granite County — 445 documented sites across 5 of the 9 source types we track.
The most significant on record: 4 Superfund sites (none NPL-listed). Sites tracked in EPA's Superfund program — from assessment-stage CERCLIS entries to confirmed National Priorities List cleanup sites.
Granite County carries one of the heavier federal records we track — and that's not a verdict on your yard. Proximity to a documented site is information, not a diagnosis: nothing here says any particular parcel is affected. It does earn one concrete step — before food beds go in the ground, a professional soil test tells you exactly what you're working with, and raised beds with clean imported soil grow well almost anywhere in the meantime.
Sources: EPA, USGS — 1.8M documented sites tracked nationwide across 9 federal source types.
What's on the federal record near Granite County
Closest first, across Granite County. Listing isn't leaking, and distance isn't exposure.
- Copper Queen GroupMining · 1.4 mi
- BLACK PINE MINING COUnderground Storage Tanks · 1.6 mi
- MDOT PHILIPSBURGUnderground Storage Tanks · 1.6 mi
- CONTACT MINING CO MILLUnderground Storage Tanks · 1.6 mi
- Black Pine DistrictMining · 4.4 mi
- Double EagleMining · 4.5 mi
- Black Pine MineMining · 4.6 mi
- Combination MineMining · 4.6 mi
- Last Chance ClaimMining · 6.2 mi
- Last Chance TailingsMining · 6.3 mi
- Peacock GroupMining · 6.8 mi
- SUNSHINE STATION 417Underground Storage Tanks · 6.9 mi
6 more sites are on the record inside the same radius. See them on the map
Measured from Granite County'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 Granite County.
Total Sites
445
across Granite County
Risk Level
High
Highest-severity
4 Superfund sites (none NPL-listed)
Sources Checked
across Granite County
Severity Distribution
across Granite County
Highest-Severity Sites
A note from Gnorman
What an experienced grower watches for around here
In and around Granite County, Mining runs higher than the national average — 374 sites across Granite County. That's not a problem with your land — it's information about it.
Mining: Mining sites — both historic and active — can leach heavy metals (arsenic, lead, cadmium, mercury) into soil and water for centuries after operations cease.
Test soil for heavy metals (lead, arsenic, cadmium, mercury) — this is essential near any mining site.
Check your specific parcel in Granite County
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 Granite County average
Your land is one point inside Granite County
Everything above resolves to Granite County as a whole — one PHZM band and one county frost record, read across 1.1M 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 county 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 county average.
Your Lot vs the Granite County Average
Granite County Average
- ●USDA Zones 5a, averaged across Granite County
- ●One soil character for all of Granite County
- ●Frost dates read at Granite County's scale: May 28 to Sep 23
YOUR Parcel
- ✓Your exact zone, not Granite County's 5a
- ✓Your SSURGO soil type & pH
- ✓Your sun exposure, cast in 3D
See MY Growing Report
Read your parcel in Granite County
Pull a site-specific report for your exact address in Granite County, Montana — soil, sun, drainage, frost risk, and scored plant recommendations.
Three things about your lot that Granite County averages can't show:
We read public map data around Granite County — soil, climate, flood, and parcel records. How we handle your address.
25+ data sources read at your address, not the Granite County average
How we know this about Granite County
The datasets: hardiness from the USDA ARS Plant Hardiness Zone Map 2023, read at county grain; hard-freeze dates from NOAA 1991–2020 28°F normals at this county’s own record where one resolves, and the labelled statewide window where none does; soils from the USDA NRCS SSURGO survey, area-weighted across the county’s own map units; boundaries and acreage from US Census TIGER/Line 2025; the contamination and pesticide records from the federal sources named in their beats above. Where Granite County carries no record of its own, the figure is inherited and labelled — the resolution ledger below names each.
Common questions about Granite County
When does frost risk typically end in Granite County?
The last hard freeze (28°F) in Granite County typically lands around May 28, 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 18.
How long is the growing season in Granite County?
Measured between 28°F hard freezes, Granite County sees about 118 frost-free days — roughly May 28 through Sep 23, per NOAA 1991–2020 climate normals. Tender crops work a shorter one: nearer Jun 18 to Sep 9, about 83 days.
Is the soil safe to grow vegetables in Granite County?
The federal record around Granite County runs heavier than most — 445 documented sites, mostly Mining entries (374), the nearest Mining record about 1.4 miles out — so test the soil before planting food in the ground, and raised beds with clean imported soil grow well in the meantime. Even here, proximity to a documented site is information, not a diagnosis of any one yard; the contamination map shows exactly what's recorded and where.
How do gardeners stretch the season in Granite County?
With about 118 frost-free days between hard freezes, Granite County 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 146 to 174 days — and cold frames or low tunnels buy more. Starting transplants indoors ahead of the May 28 hard-freeze normal stretches the season without touching the calendar.
Everything above is measured at Granite County's scale — its 5a band and its 118-day season. Your yard writes its own version of Granite County's numbers: we read soil, sun, drainage and frost at your exact address. Try it for 14 days — no card required.
Will It Grow Here?
Zone fit is the first question — each answer below reads Montana's frost window, season length, and soil profile against the plant's real requirements.
What this page reads at Granite County’s own scale
8 of the readings below were taken at Granite County's own scale — its own ~118-day span between 28°F freezes, the 3 most extensive soil series mapped here and 445 documented sites inside its boundary; one is borrowed from a wider read, named and linked below.
Measured here
- Granite County's own USDA hardiness band, zones 5aUSDA PHZM 2023
- Granite County's own 28°F hard-freeze dates and its ~118-day span between themNOAA 1991–2020 Climate Normals
- The soil order, drainage, surface pH, and the 3 most extensive named soil series mapped in Granite CountyUSDA NRCS SSURGO
- 445 documented contamination sites inside the county boundary, distance-sorted from its center — the closest Mining record about 1.4 miles outFederal environmental registers
- Granite County's boundary and the 1,105,383 acres inside itUS Census TIGER/Line 2025
- Which of 1,086 plants clear zones 5a and a ~118-day seasonGrowable Ground crop-matching engine
- Granite County sitting wholly inside the Middle RockiesUS EPA Level III Ecoregions
- Which agricultural compounds go onto Granite County farmland, and roughly how muchUSGS NAWQA EPest county estimates
Inherited from a wider read
- The growing challenges every Montana grower plans around — written at state scale, so they stay on the state guidefrom Montana
What this page can’t tell you
- How the season shifts across Granite County — the ~118 days above is one reading at its centre; the 12 towns below each carry their owntowns in this county →
- The soil pH, drainage, sun hours, and frost pockets on any one lot among Granite County's 1,105,383 acreswhy one lot differs from the next →
- Which of those 445 documented sites actually reaches your soil — that needs your address, the wind, and the groundwater directionhow we read the record →
- Where cold air settles, which slopes face the sun, and which way the wind runs on your own ground — none of it survives being averaged over Granite Countyread your own land →