Lost River, Idaho, sits in USDA hardiness zone 5a — a band that supports both cool-season staples and warm-season crops chosen to fit the local frost window.
Expect pumpkin, cranberry, lavender, and zucchini to be strong candidates here; the deciding factors on any one parcel stay local — soil, sun, and drainage.
Even in Lost River, 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 Lost River 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 Lost River — soil, climate, flood, and parcel records. How we handle your address.
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Lost River — the short answer
Lost River, Idaho: USDA zone 5a, about 107 days between hard freezes, across 5K acres of city.
- USDA zone
- 5a
- USDA PHZM 2023
- Last hard freeze (28°F)
- Jun 2
- NOAA 1991–2020 Climate Normals, 28°F — this town
- First hard freeze (28°F)
- Sep 17
- NOAA 1991–2020 Climate Normals, 28°F — this town
- Days between freezes
- ~107
- NOAA 1991–2020 Climate Normals, 28°F — this town
- City area
- 5K 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 Lost River's average, not your lot's — a low corner or a tree line moves it. Against Lost River's 107-day season, see what your own ground reads.
Soil varies lot by lot — soil types explained.
What this means for growing in Lost River
Each reading below is measured for Lost River itself — here is what it means for a garden here, and the move an experienced grower makes about it.
Season length
MeasuredLost River runs about 107 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
MeasuredLost River 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 Lost River is in
Lost River sits in the Middle Rockies — EPA Level III, inside the wider Northwestern Forested Mountains. That is read at Lost River's own centroid, and it is not what its county reads: Custer County is mostly Idaho Batholith. The wider page above you is answering a different question about different ground.
What Grows in Lost River
Every plant below cleared Lost River's own zone 5a and its 107-day season. Each card opens that plant's Idaho profile. How we score.
Is it too late to plant in Lost River?
Almost never — the real question is what to plant next. Cool-season crops can go in from around May 5; tender transplants wait until two to three weeks after the last 28°F hard freeze, which lands near Jun 2 (NOAA 1991–2020 climate normals); and from midsummer, planting counts back from the first fall freeze around Sep 17 — long-season crops need about 90 days of runway, quick greens only 30. In a season this compact, fast finishers and cold-hardy greens do the late work, and garlic tucked in before the freeze repays you next summer.
What's on the federal record near Lost River
Closest first, within ~10 miles of Lost River. Listing isn't leaking, and distance isn't exposure.
- 05N 24E 36CACB1Nitrate · 4.7 mi
- Lead Belt MineMining · 6.1 mi
- Reliance MineMining · 6.4 mi
- Ella MineMining · 6.4 mi
- St. Louis MineMining · 6.8 mi
- Saint Louis MineMining · 6.8 mi
- Hornsilver MineMining · 7.0 mi
- Butte - Antelope MineMining · 7.0 mi
- USDOI BLM CHAMPAGNE CREEK MINESuperfund · 7.2 mi
- Last Chance MineMining · 7.5 mi
- Silver BellMining · 9.6 mi
Measured from Lost River'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 Lost River.
Total Sites
12
within ~10 miles of Lost River
Risk Level
Elevated
Highest-severity
1 Superfund site (none NPL-listed)
Severity Distribution
within ~10 miles of Lost River
Highest-Severity Sites
Know Before You Grow
- •Mine waste leaches heavy metals. Test for lead, arsenic and cadmium before growing food here.
- •On a private well, test for nitrates: above 10 mg/L the water needs treatment before irrigating.
- •A Superfund listing means federally documented contamination. Test soil and water before planting edibles nearby.
Check your specific parcel in Lost River
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 Lost River average
Your land is one point inside Lost River
Everything above resolves to Lost River as a whole — one PHZM band and one 28°F frost record, read across 5K 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 Lost River Average
Lost River Average
- ●USDA Zones 5a, averaged across Lost River
- ●One soil character for all of Lost River
- ●Frost dates read at Lost River's scale: Jun 2 to Sep 17
YOUR Parcel
- ✓Your exact zone, not Lost River's 5a
- ✓Your SSURGO soil type & pH
- ✓Your sun exposure, cast in 3D
See MY Growing Report
Read your specific parcel in Lost River
Pull a site-specific report for your exact address in Lost River, Idaho — soil, sun, drainage, frost risk, and scored plant recommendations.
Three things about your lot that Lost River averages can't show:
We read public map data around Lost River — soil, climate, flood, and parcel records. How we handle your address.
25+ data sources read at your address, not the Lost River average
How we know this about Lost River
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 Lost River’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 Lost River
When does frost risk typically end in Lost River?
The last hard freeze (28°F) in Lost River typically lands around Jun 2, 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 23.
When is the first frost in Lost River?
The first hard freeze (28°F) in Lost River typically arrives around Sep 17, per NOAA 1991–2020 climate normals — the point tender summer crops finish. Lighter frosts run ahead of it, near Sep 3, so the watching starts about Aug 18 — about 107 days after the spring freeze cleared.
How long is the growing season in Lost River?
Measured between 28°F hard freezes, Lost River sees about 107 frost-free days — roughly Jun 2 through Sep 17, per NOAA 1991–2020 climate normals. Tender crops work a shorter one: nearer Jun 23 to Sep 3, about 72 days.
Is the soil safe to grow vegetables in Lost River?
The federal record around Lost River is a meaningful one — 12 documented sites, mostly Mining entries (9), the nearest Nitrate record about 4.7 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 Lost River?
With about 107 frost-free days between hard freezes, Lost River 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 135 to 163 days — and cold frames or low tunnels buy more. Starting transplants indoors ahead of the Jun 2 hard-freeze normal stretches the season without touching the calendar.
Everything above is measured at Lost River's scale — its 5a band and its 107-day season. Your yard writes its own version of Lost River'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 Lost River’s own scale
6 of the readings below were taken at Lost River's own scale — its own ~107-day season between 28°F freezes, the 5,324 acres it covers and 12 documented sites around it; 4 are borrowed from a wider read, named and linked below.
Measured here
- Lost River's own USDA hardiness band, zones 5aUSDA PHZM 2023
- Lost River's own 28°F hard-freeze dates, about Jun 2 and Sep 17 and the ~107-day span between themNOAA 1991–2020 Climate Normals
- 12 documented contamination sites on the federal record near Lost River, the closest Nitrate record about 4.7 miles out from the town centreFederal environmental registers
- Lost River's boundary and the 5,324 acres inside itUS Census TIGER/Line 2025
- Which of 1,086 plants clear zones 5a and a ~107-day seasonGrowable Ground crop-matching engine
- Lost River sits in the Middle Rockies — not the ecoregion its county mostly readsUS EPA Level III Ecoregions
Inherited from a wider read
- Soil character — no town-scale survey exists, so Lost River's 5,324 acres read through its county's SSURGO summaryfrom Custer County
- Growing-degree days and winter chill — measured county-wide only, so the county page carries themfrom Custer County
- The growing challenges every Idaho grower plans around — written at state scale, so they stay on the state guidefrom Idaho
- Butterfly and beetle records, and the farmland pesticide estimate — all published county-widefrom Custer County
What this page can’t tell you
- The soil pH, drainage, sun hours, and frost pockets on any one lot among Lost River's 5,324 acreswhy one lot differs from the next →
- Which side of Lost River you're on — a low spot frosts first and a south wall warms early, and one normal is being asked to speak for all 5,324 acresreading your own microclimate →
- How close that record sits to YOUR lot — the closest Nitrate record about 4.7 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 Lost River-wide figureread your own land →
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