Troy, Idaho, sits in USDA hardiness zone 6b — room for a real mix of vegetables, fruit, and perennials matched to the local frost calendar.
A short list that earns its place here — cabbage, blackberry, california poppy, and collard greens — with any one site's soil, sun, and drainage making the final cut.
Even in Troy, 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 Troy 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 Troy — soil, climate, flood, and parcel records. How we handle your address.
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Troy — the short answer
Troy, Idaho: USDA zone 6b, about 186 days between hard freezes, across 506 acres of city.
- USDA zone
- 6b
- USDA PHZM 2023
- Last hard freeze (28°F)
- Apr 17
- NOAA 1991–2020 Climate Normals, 28°F — this town
- First hard freeze (28°F)
- Oct 20
- NOAA 1991–2020 Climate Normals, 28°F — this town
- Days between freezes
- ~186
- NOAA 1991–2020 Climate Normals, 28°F — this town
- City area
- 506 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 6b is Troy's average, not your lot's — a low corner or a tree line moves it. Against Troy's 186-day season, see what your own ground reads.
Soil varies lot by lot — soil types explained.
What this means for growing in Troy
Each reading below is measured for Troy itself — here is what it means for a garden here, and the move an experienced grower makes about it.
Season length
MeasuredTroy runs about 186 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
MeasuredTroy sits in USDA hardiness zone 6b.
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 Troy is in
Troy sits in the Northern Rockies — EPA Level III, inside the wider Northwestern Forested Mountains. That is read at Troy's own centroid rather than borrowed from Latah County.
What Grows in Troy
Every plant below cleared Troy's own zone 6b and its 186-day season. Each card opens that plant's Idaho profile. How we score.
Is it too late to plant in Troy?
Usually not — gardeners here simply switch what goes in the ground as the season moves. Cool-season crops can go in from around Mar 20; tender transplants wait until two to three weeks after the last 28°F hard freeze, which lands near Apr 17 (NOAA 1991–2020 climate normals); and from midsummer, planting counts back from the first fall freeze around Oct 20 — long-season crops need about 90 days of runway, quick greens only 30. Even past midsummer there is room for a true fall garden here, and garlic planted near the close carries the momentum into next year.
What's on the federal record near Troy
Closest first, within ~10 miles of Troy. Listing isn't leaking, and distance isn't exposure.
- SUNSET MART #10Underground Storage Tanks · 500 ft
- IDAHO CEDAR SALESUnderground Storage Tanks · 1500 ft
- OMER DRURYUnderground Storage Tanks · 1500 ft
- TROY COMPUTERS #1 & 2Underground Storage Tanks · 1500 ft
- STROM ELECTRICBrownfields · 1600 ft
- RICHARD GLUDT/HOMETOWN SERVICEUnderground Storage Tanks · 1600 ft
- WHITEPINE JT SCHOOL DISTUnderground Storage Tanks · 1800 ft
- TROY CHEVRONUnderground Storage Tanks · 1900 ft
- 39N 03W 07DAC1Nitrate · 0.9 mi
- ZIMMERMAN LOGGING CO.Underground Storage Tanks · 1.3 mi
- LITTLER FARMUnderground Storage Tanks · 1.6 mi
- 39N 03W 10CAB1Nitrate · 3.4 mi
6 more sites are on the record inside the same radius. See them on the map
Measured from Troy'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 Troy.
Sources Checked
within ~10 miles of Troy
Severity Distribution
within ~10 miles of Troy
Highest-Severity Sites
A note from Gnorman
What an experienced grower watches for around here
In and around Troy, two things run higher than the national average within ~10 miles of Troy — Nitrate (38 sites) and Mining (5 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 Troy
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 Troy average
Your land is one point inside Troy
Everything above resolves to Troy as a whole — one PHZM band and one 28°F frost record, read across 506 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 Troy Average
Troy Average
- ●USDA Zones 6b, averaged across Troy
- ●One soil character for all of Troy
- ●Frost dates read at Troy's scale: Apr 17 to Oct 20
YOUR Parcel
- ✓Your exact zone, not Troy's 6b
- ✓Your SSURGO soil type & pH
- ✓Your sun exposure, cast in 3D
See MY Growing Report
Read your specific parcel in Troy
Pull a site-specific report for your exact address in Troy, Idaho — soil, sun, drainage, frost risk, and scored plant recommendations.
Three things about your lot that Troy averages can't show:
We read public map data around Troy — soil, climate, flood, and parcel records. How we handle your address.
25+ data sources read at your address, not the Troy average
How we know this about Troy
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 Troy’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 Troy
When does frost risk typically end in Troy?
The last hard freeze (28°F) in Troy typically lands around Apr 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 May 8.
When is the first frost in Troy?
The first hard freeze (28°F) in Troy typically arrives around Oct 20, per NOAA 1991–2020 climate normals — the point tender summer crops finish. Lighter frosts run ahead of it, near Oct 6, so the watching starts about Sep 20 — about 186 days after the spring freeze cleared.
How long is the growing season in Troy?
Measured between 28°F hard freezes, Troy sees about 186 frost-free days — roughly Apr 17 through Oct 20, per NOAA 1991–2020 climate normals. Tender crops work a shorter one: nearer May 8 to Oct 6, about 151 days.
Is the soil safe to grow vegetables in Troy?
The federal record around Troy shows 68 documented sites, mostly Nitrate entries (38), the nearest Underground Storage Tanks record under a tenth of a mile out — a typical footprint for a growing area, and proximity to a documented site is information, not a diagnosis of any one yard. It's worth seeing which recorded sites sit closest to where you grow, and testing the soil before new food beds near any of them.
How do I protect my plants from frost in Troy?
From about Sep 20 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 20 (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 20. Hardy greens and roots shrug off light frost and sweeten after it — leave them in.
Everything above is measured at Troy's scale — its 6b band and its 186-day season. Your yard writes its own version of Troy'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 Troy’s own scale
6 of the readings below were taken at Troy's own scale — its own ~186-day season between 28°F freezes, the 506 acres it covers and 68 documented sites around it; 4 are borrowed from a wider read, named and linked below.
Measured here
- Troy's own USDA hardiness band, zones 6bUSDA PHZM 2023
- Troy's own 28°F hard-freeze dates, about Apr 17 and Oct 20 and the ~186-day span between themNOAA 1991–2020 Climate Normals
- 68 documented contamination sites on the federal record near Troy, the closest Underground Storage Tanks record under a tenth of a mile out from the town centreFederal environmental registers
- Troy's boundary and the 506 acres inside itUS Census TIGER/Line 2025
- Which of 1,086 plants clear zones 6b and a ~186-day seasonGrowable Ground crop-matching engine
- The ecoregion at Troy's own centroid, the Northern RockiesUS EPA Level III Ecoregions
Inherited from a wider read
- Soil character — no town-scale survey exists, so Troy's 506 acres read through its county's SSURGO summaryfrom Latah County
- Growing-degree days and winter chill — measured county-wide only, so the county page carries themfrom Latah 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 Latah County
What this page can’t tell you
- The soil pH, drainage, sun hours, and frost pockets on any one lot among Troy's 506 acreswhy one lot differs from the next →
- Which side of Troy you're on — a low spot frosts first and a south wall warms early, and one normal is being asked to speak for all 506 acresreading your own microclimate →
- How close that record sits to YOUR lot — the closest Underground Storage Tanks 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 Troy-wide figureread your own land →
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