Helena, Montana, sits in USDA hardiness zone 4b — a range where zone-matched perennials and frost-aware annual timing set what succeeds.
Among the crops suited to this profile: cabbage, cranberry, turkish rocket, and collard greens. The site-level story — soil, sun, drainage — decides the rest.
Even in Helena, 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 Helena 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 Helena — soil, climate, flood, and parcel records. How we handle your address.
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Helena — the short answer
Helena, Montana: USDA zone 4b, about 156 days between hard freezes, across 11K acres of city.
- USDA zone
- 4b
- USDA PHZM 2023
- Last hard freeze (28°F)
- May 3
- NOAA 1991–2020 Climate Normals, 28°F — this town
- First hard freeze (28°F)
- Oct 6
- NOAA 1991–2020 Climate Normals, 28°F — this town
- Days between freezes
- ~156
- NOAA 1991–2020 Climate Normals, 28°F — this town
- City area
- 11K 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 Helena's average, not your lot's — a low corner or a tree line moves it. Against Helena's 156-day season, see what your own ground reads.
Soil varies lot by lot — soil types explained.
What this means for growing in Helena
Each reading below is measured for Helena itself — here is what it means for a garden here, and the move an experienced grower makes about it.
Season length
MeasuredHelena runs about 156 days between hard freezes — a moderate growing season.
There is room for the full run of cool-season crops plus a warm-season main crop, but the calendar is tight enough that a late spring or early fall frost still decides how much finishes.
Time warm-season transplants to your last hard freeze, and a few weeks of season extension turns a near-miss harvest into a sure one.
NOAA 1991–2020 Climate Normals
Winter hardiness
MeasuredHelena 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 Helena is in
Helena sits in the Middle Rockies — EPA Level III, inside the wider Northwestern Forested Mountains. That is read at Helena's own centroid rather than borrowed from Lewis and Clark County.
What Grows in Helena
Every plant below cleared Helena's own zone 4b and its 156-day season. Each card opens that plant's Montana profile. How we score.
Is it too late to plant in Helena?
Too late for some crops, right on time for others — a growing season is a sequence, not a deadline. Cool-season crops can go in from around Apr 5; tender transplants wait until two to three weeks after the last 28°F hard freeze, which lands near May 3 (NOAA 1991–2020 climate normals); and from midsummer, planting counts back from the first fall freeze around Oct 6 — long-season crops need about 90 days of runway, quick greens only 30. Late in the year the fall bench takes over — quick greens, radishes, and garlic that repays you next summer.
What's on the federal record near Helena
Closest first, within ~10 miles of Helena. Listing isn't leaking, and distance isn't exposure.
- MR WISE CLEANERS HELENABrownfields · 350 ft
- HELENA SOLVENT SITE SOIL VAPOR EXTRACTION SYSTEMBrownfields · 350 ft
- JUNCTION ETHANOL CARD STOPUnderground Storage Tanks · 450 ft
- CAIRD ENGINEERING WORKSUnderground Storage Tanks · 550 ft
- U HAUL CENTER OF HELENAUnderground Storage Tanks · 750 ft
- SMITHAM BROTHERS AUTOMOTIVEBrownfields · 900 ft
- COLUMBIA PAINT & COATINGS CO HLN LYNDALEBrownfields · 950 ft
- HELENA MOTOR REPAIR INCUnderground Storage Tanks · 1000 ft
- MERGENTHALER TRANSFER & STORAGE MONTANA AVEUnderground Storage Tanks · 1000 ft
- PACIFIC HIDE AND FUR HELENAUnderground Storage Tanks · 1100 ft
- SMITH TRANSMISSIONBrownfields · 1100 ft
- A 1 RENTALS INC HELENAUnderground Storage Tanks · 1100 ft
6 more sites are on the record inside the same radius. See them on the map
Measured from Helena'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 Helena.
Sources Checked
within ~10 miles of Helena
Severity Distribution
within ~10 miles of Helena
Highest-Severity Sites
A note from Gnorman
What an experienced grower watches for around here
In and around Helena, two things run higher than the national average within ~10 miles of Helena — Nitrate (672 sites) and Mining (123 sites). It's not cause for alarm — it's worth knowing, and there's a sensible way to grow around it.
Nitrate: Nitrate contamination primarily comes from agricultural fertilizer runoff and failing septic systems.
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 well water for nitrate if you rely on a private well for irrigation (EPA standard: 10 mg/L).
Test soil for heavy metals (lead, arsenic, cadmium, mercury) — this is essential near any mining site.
Check your specific parcel in Helena
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 Helena average
Your land is one point inside Helena
Everything above resolves to Helena as a whole — one PHZM band and one 28°F frost record, read across 11K 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 Helena Average
Helena Average
- ●USDA Zones 4b, averaged across Helena
- ●One soil character for all of Helena
- ●Frost dates read at Helena's scale: May 3 to Oct 6
YOUR Parcel
- ✓Your exact zone, not Helena's 4b
- ✓Your SSURGO soil type & pH
- ✓Your sun exposure, cast in 3D
See MY Growing Report
Read your specific parcel in Helena
Pull a site-specific report for your exact address in Helena, Montana — soil, sun, drainage, frost risk, and scored plant recommendations.
Three things about your lot that Helena averages can't show:
We read public map data around Helena — soil, climate, flood, and parcel records. How we handle your address.
25+ data sources read at your address, not the Helena average
How we know this about Helena
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 at Helena’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 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 Helena
When does frost risk typically end in Helena?
The last hard freeze (28°F) in Helena typically lands around May 3, 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 24.
When is the first frost in Helena?
The first hard freeze (28°F) in Helena typically arrives around Oct 6, per NOAA 1991–2020 climate normals — the point tender summer crops finish. Lighter frosts run ahead of it, near Sep 22, so the watching starts about Sep 6 — about 156 days after the spring freeze cleared.
How long is the growing season in Helena?
Measured between 28°F hard freezes, Helena sees about 156 frost-free days — roughly May 3 through Oct 6, per NOAA 1991–2020 climate normals. Tender crops work a shorter one: nearer May 24 to Sep 22, about 121 days.
Is the soil safe to grow vegetables in Helena?
The federal record around Helena runs heavier than most — 1,153 documented sites, mostly Nitrate entries (672), the nearest Brownfields record under a tenth of a mile 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 I protect my plants from frost in Helena?
From about Sep 6 the job here turns from planting to protecting — the last start even a 30-day crop can finish. As the season closes around the first 28°F hard freeze near Oct 6 (NOAA 1991–2020 climate normals), 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 Oct 6. Hardy greens and roots shrug off light frost and sweeten after it — leave them in.
Everything above is measured at Helena's scale — its 4b band and its 156-day season. Your yard writes its own version of Helena'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 Helena’s own scale
6 of the readings below were taken at Helena's own scale — its own ~156-day season between 28°F freezes, the 10,988 acres it covers and 1,153 documented sites around it; 4 are borrowed from a wider read, named and linked below.
Measured here
- Helena's own USDA hardiness band, zones 4bUSDA PHZM 2023
- Helena's own 28°F hard-freeze dates, about May 3 and Oct 6 and the ~156-day span between themNOAA 1991–2020 Climate Normals
- 1,153 documented contamination sites on the federal record near Helena, the closest Brownfields record under a tenth of a mile out from the town centreFederal environmental registers
- Helena's boundary and the 10,988 acres inside itUS Census TIGER/Line 2025
- Which of 1,086 plants clear zones 4b and a ~156-day seasonGrowable Ground crop-matching engine
- The ecoregion at Helena's own centroid, the Middle RockiesUS EPA Level III Ecoregions
Inherited from a wider read
- Soil character — no town-scale survey exists, so Helena's 10,988 acres read through its county's SSURGO summaryfrom Lewis and Clark County
- Growing-degree days and winter chill — measured county-wide only, so the county page carries themfrom Lewis and Clark 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 Lewis and Clark County
What this page can’t tell you
- The soil pH, drainage, sun hours, and frost pockets on any one lot among Helena's 10,988 acreswhy one lot differs from the next →
- Which side of Helena you're on — a low spot frosts first and a south wall warms early, and one normal is being asked to speak for all 10,988 acresreading your own microclimate →
- How close that record sits to YOUR lot — the closest Brownfields record under a tenth of a mile 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 Helena-wide figureread your own land →
More in Montana
Wider growing context
What grows across MontanaHelena sits outside our named growing regions, so Montana as a whole is its closest context here.
Nearby growing guides