Cardwell, Montana, sits in USDA hardiness zone 5a — enough range to grow cool-season vegetables, hardy fruit, and warm-season crops that mature before the first hard frost.
Well-matched crops include cabbage, cranberry, lavender, and collard greens, and the gap between "grows in the area" and "grows in your yard" is closed by soil, sun, and drainage.
Even in Cardwell, 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 Cardwell 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 Cardwell — soil, climate, flood, and parcel records. How we handle your address.
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Cardwell — the short answer
Cardwell, Montana: USDA zone 5a, about 149 days between hard freezes, across 1K acres of town.
- USDA zone
- 5a
- USDA PHZM 2023
- Last hard freeze (28°F)
- May 6
- NOAA 1991–2020 Climate Normals, 28°F — this town
- First hard freeze (28°F)
- Oct 2
- NOAA 1991–2020 Climate Normals, 28°F — this town
- Days between freezes
- ~149
- NOAA 1991–2020 Climate Normals, 28°F — this town
- Town area
- 1K 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 5a is Cardwell's average, not your lot's — a low corner or a tree line moves it. Against Cardwell's 149-day season, see what your own ground reads.
Soil varies lot by lot — soil types explained.
What this means for growing in Cardwell
Each reading below is measured for Cardwell itself — here is what it means for a garden here, and the move an experienced grower makes about it.
Season length
MeasuredCardwell runs about 149 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
MeasuredCardwell 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 Cardwell is in
Cardwell sits in the Middle Rockies — EPA Level III, inside the wider Northwestern Forested Mountains. That is read at Cardwell's own centroid rather than borrowed from Jefferson County.
What Grows in Cardwell
Every plant below cleared Cardwell's own zone 5a and its 149-day season. Each card opens that plant's Montana profile. How we score.
Is it too late to plant in Cardwell?
Usually not — gardeners here simply switch what goes in the ground as the season moves. Cool-season crops can go in from around Apr 8; tender transplants wait until two to three weeks after the last 28°F hard freeze, which lands near May 6 (NOAA 1991–2020 climate normals); and from midsummer, planting counts back from the first fall freeze around Oct 2 — 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 Cardwell
Closest first, within ~10 miles of Cardwell. Listing isn't leaking, and distance isn't exposure.
- 01N03W03DCCD01Nitrate · 2300 ft
- MDOT WHITEHALL MAINTENANCEUnderground Storage Tanks · 0.5 mi
- FELLS STOREUnderground Storage Tanks · 0.6 mi
- JOHN HOWARD MULLIGANUnderground Storage Tanks · 0.7 mi
- CARDWELL STORE LLCUnderground Storage Tanks · 0.8 mi
- CARDWELL SCHOOL DIST 16 & 31Underground Storage Tanks · 0.8 mi
- 01N03W02BACB01Nitrate · 1.1 mi
- Butte CardwellMining · 1.7 mi
- Hope MineMining · 1.8 mi
- HopeMining · 2.2 mi
- GOLDEN SUNLIGHT MINES INC USTUnderground Storage Tanks · 2.2 mi
- Golden SunlightMining · 3.3 mi
6 more sites are on the record inside the same radius. See them on the map
Measured from Cardwell'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 Cardwell.
Total Sites
114
within ~10 miles of Cardwell
Risk Level
High
Highest-severity
1 Toxics Release Inventory facility
Sources Checked
within ~10 miles of Cardwell
Severity Distribution
within ~10 miles of Cardwell
Highest-Severity Sites
A note from Gnorman
What an experienced grower watches for around here
In and around Cardwell, Mining runs higher than the national average — 59 sites within ~10 miles of Cardwell. It's not cause for alarm — it's worth knowing, and there's a sensible way to grow around 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 Cardwell
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 Cardwell average
Your land is one point inside Cardwell
Everything above resolves to Cardwell as a whole — one PHZM band and one 28°F frost record, read across 1K 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 Cardwell Average
Cardwell Average
- ●USDA Zones 5a, averaged across Cardwell
- ●One soil character for all of Cardwell
- ●Frost dates read at Cardwell's scale: May 6 to Oct 2
YOUR Parcel
- ✓Your exact zone, not Cardwell's 5a
- ✓Your SSURGO soil type & pH
- ✓Your sun exposure, cast in 3D
See MY Growing Report
Read your specific parcel in Cardwell
Pull a site-specific report for your exact address in Cardwell, Montana — soil, sun, drainage, frost risk, and scored plant recommendations.
Three things about your lot that Cardwell averages can't show:
We read public map data around Cardwell — soil, climate, flood, and parcel records. How we handle your address.
25+ data sources read at your address, not the Cardwell average
How we know this about Cardwell
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 Cardwell’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 Cardwell
When does frost risk typically end in Cardwell?
The last hard freeze (28°F) in Cardwell typically lands around May 6, 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 27.
When is the first frost in Cardwell?
The first hard freeze (28°F) in Cardwell typically arrives around Oct 2, per NOAA 1991–2020 climate normals — the point tender summer crops finish. Lighter frosts run ahead of it, near Sep 18, so the watching starts about Sep 2 — about 149 days after the spring freeze cleared.
How long is the growing season in Cardwell?
Measured between 28°F hard freezes, Cardwell sees about 149 frost-free days — roughly May 6 through Oct 2, per NOAA 1991–2020 climate normals. Tender crops work a shorter one: nearer May 27 to Sep 18, about 114 days.
Is the soil safe to grow vegetables in Cardwell?
The federal record around Cardwell runs heavier than most — 114 documented sites, mostly Mining entries (59), the nearest Nitrate record about 0.4 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 Cardwell?
With about 149 frost-free days between hard freezes, Cardwell 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 177 to 205 days — and cold frames or low tunnels buy more. Starting transplants indoors ahead of the May 6 hard-freeze normal stretches the season without touching the calendar.
Everything above is measured at Cardwell's scale — its 5a band and its 149-day season. Your yard writes its own version of Cardwell'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 Cardwell’s own scale
6 of the readings below were taken at Cardwell's own scale — its own ~149-day season between 28°F freezes, the 1,374 acres it covers and 114 documented sites around it; 4 are borrowed from a wider read, named and linked below.
Measured here
- Cardwell's own USDA hardiness band, zones 5aUSDA PHZM 2023
- Cardwell's own 28°F hard-freeze dates, about May 6 and Oct 2 and the ~149-day span between themNOAA 1991–2020 Climate Normals
- 114 documented contamination sites on the federal record near Cardwell, the closest Nitrate record about 0.4 miles out from the town centreFederal environmental registers
- Cardwell's boundary and the 1,374 acres inside itUS Census TIGER/Line 2025
- Which of 1,086 plants clear zones 5a and a ~149-day seasonGrowable Ground crop-matching engine
- The ecoregion at Cardwell's own centroid, the Middle RockiesUS EPA Level III Ecoregions
Inherited from a wider read
- Soil character — no town-scale survey exists, so Cardwell's 1,374 acres read through its county's SSURGO summaryfrom Jefferson County
- Growing-degree days and winter chill — measured county-wide only, so the county page carries themfrom Jefferson 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 Jefferson County
What this page can’t tell you
- The soil pH, drainage, sun hours, and frost pockets on any one lot among Cardwell's 1,374 acreswhy one lot differs from the next →
- Which side of Cardwell you're on — a low spot frosts first and a south wall warms early, and one normal is being asked to speak for all 1,374 acresreading your own microclimate →
- How close that record sits to YOUR lot — the closest Nitrate record about 0.4 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 Cardwell-wide figureread your own land →
More in Montana
Wider growing context
What grows across MontanaCardwell sits outside our named growing regions, so Montana as a whole is its closest context here.
Nearby growing guides