Bonner County, in 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.
Bonner County lies within the Idaho Panhandle (North Idaho) — a regional growing area with its own character.
Grounded in USDA PHZM 2023 · Growable Ground suitability scoring · NOAA 1991–2020 Climate Normals
Bonner County holds more than one microclimate.
Soils and elevations shift across Bonner 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 Bonner County — soil, climate, flood, and parcel records. How we handle your address.
No card required · your full report in seconds
Bonner County — the short answer
Bonner County, Idaho: USDA zone 6b, about 187 days between hard freezes, across 1.1M acres.
- USDA zone
- 6b
- USDA PHZM 2023
- Last hard freeze (28°F)
- Apr 21
- NOAA 1991–2020 Climate Normals, 28°F
- First hard freeze (28°F)
- Oct 25
- NOAA 1991–2020 Climate Normals, 28°F
- Days between freezes
- ~187
- 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 6b is Bonner County's average, not your lot's — a low corner or a tree line moves it. Against Bonner County's 187-day season, see what your own ground reads.
Heat in Bonner County
Across a year, Bonner County accumulates about 1,078 growing degree days above 50°F, about 413 fewer than the middle Idaho county — ahead of 9 of Idaho’s 44 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 Bonner County
Across Bonner County, the ground is predominantly Andisols, where Pend Oreille, Bonner, and Vay are the most extensive named soil series. The soil is generally well drained with a ashy silt loam surface. Topsoil pH runs about 6.3–6.5, slightly acidic. Rainfall drains through hydrologic group B soils.
Soil order
Andisols
Drainage
Well drained
Prime farmland
9%
Hydric soils
4%
Soil still varies lot by lot — soil types explained.
How the ground varies across Bonner County
The USDA soil survey maps 76% of Bonner County as well drained — but another 14% drains differently: 6% moderately well drained, 4% somewhat poorly drained.
Pend Oreille is the most extensive named soil at 10% of mapped acres, then Bonner (7%) and Vay (4%).
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 Bonner County
Each reading below is measured for Bonner 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 Bonner 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 Bonner County runs about pH 6.3–6.5, 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
MeasuredBonner County runs about 187 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
MeasuredBonner County 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 Bonner County is in
Bonner County sits in the Northern Rockies — EPA Level III, inside the wider Northwestern Forested Mountains. One consistent ecological setting across the whole county.
What Grows in Bonner County
We scored all 1,086 plants against Bonner County's own USDA zone 6b and its own 187-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 Idaho profile.
Is it too late to plant in Bonner County?
Usually not — gardeners here simply switch what goes in the ground as the season moves. Cool-season crops can go in from around Mar 24; tender transplants wait until two to three weeks after the last 28°F hard freeze, which lands near Apr 21 (NOAA 1991–2020 climate normals); and from midsummer, planting counts back from the first fall freeze around Oct 25 — 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 gets applied to farmland in Bonner County
USGS estimates 1,040 lb of Glyphosate on Bonner County farmland in 2019, its largest by weight, ahead of 2,4-d (543 lb) and Atrazine (401 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 Bonner County — and how to grow with it.
We checked the federal record across Bonner County — 627 documented sites across 7 of the 9 source types we track.
The most significant on record: 7 Superfund sites (none NPL-listed). Sites tracked in EPA's Superfund program — from assessment-stage CERCLIS entries to confirmed National Priorities List cleanup sites.
Bonner 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 Bonner County
Closest first, across Bonner County. Listing isn't leaking, and distance isn't exposure.
- FlowerMining · 1.3 mi
- Big Hill MineMining · 2.2 mi
- Cabinet RangeMining · 2.3 mi
- SCHWEITZER MTN RESORTUnderground Storage Tanks · 2.9 mi
- 57N 02W 16BAC1Nitrate · 3.0 mi
- SANDPOINT ORGANIC AGRICULTURE CENTERBrownfields · 3.2 mi
- AMAZON.COM SERVICES LLC - WID8Brownfields · 3.2 mi
- KODIAK AIRCRAFT CO INCBrownfields · 3.3 mi
- Little CasinoMining · 3.4 mi
- Big CasinoMining · 3.4 mi
- Idaho PanhandleMining · 3.4 mi
- BONNER COUNTY ROAD DEPT SHOP #3Underground Storage Tanks · 3.6 mi
6 more sites are on the record inside the same radius. See them on the map
Measured from Bonner 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 Bonner County.
Sources Checked
across Bonner County
Severity Distribution
across Bonner County
Highest-Severity Sites
A note from Gnorman
What an experienced grower watches for around here
In and around Bonner County, Mining runs higher than the national average — 251 sites across Bonner County. Knowing it is half the work — and it's nothing a thoughtful grower can't plan for.
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 Bonner 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 Bonner County average
Your land is one point inside Bonner County
Everything above resolves to Bonner 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 Bonner County Average
Bonner County Average
- ●USDA Zones 6b, averaged across Bonner County
- ●One soil character for all of Bonner County
- ●Frost dates read at Bonner County's scale: Apr 21 to Oct 25
YOUR Parcel
- ✓Your exact zone, not Bonner County's 6b
- ✓Your SSURGO soil type & pH
- ✓Your sun exposure, cast in 3D
See MY Growing Report
Read your parcel in Bonner County
Pull a site-specific report for your exact address in Bonner County, Idaho — soil, sun, drainage, frost risk, and scored plant recommendations.
Three things about your lot that Bonner County averages can't show:
We read public map data around Bonner County — soil, climate, flood, and parcel records. How we handle your address.
25+ data sources read at your address, not the Bonner County average
How we know this about Bonner 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 Bonner County carries no record of its own, the figure is inherited and labelled — the resolution ledger below names each.
Common questions about Bonner County
When does frost risk typically end in Bonner County?
The last hard freeze (28°F) in Bonner County typically lands around Apr 21, 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 12.
How long is the growing season in Bonner County?
Measured between 28°F hard freezes, Bonner County sees about 187 frost-free days — roughly Apr 21 through Oct 25, per NOAA 1991–2020 climate normals. Tender crops work a shorter one: nearer May 12 to Oct 11, about 152 days.
Is the soil safe to grow vegetables in Bonner County?
The federal record around Bonner County runs heavier than most — 627 documented sites, mostly Mining entries (251), the nearest Mining record about 1.3 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.
Everything above is measured at Bonner County's scale — its 6b band and its 187-day season. Your yard writes its own version of Bonner 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 Idaho's frost window, season length, and soil profile against the plant's real requirements.
What this page reads at Bonner County’s own scale
8 of the readings below were taken at Bonner County's own scale — its own ~187-day span between 28°F freezes, the 3 most extensive soil series mapped here and 627 documented sites inside its boundary; one is borrowed from a wider read, named and linked below.
Measured here
- Bonner County's own USDA hardiness band, zones 6bUSDA PHZM 2023
- Bonner County's own 28°F hard-freeze dates and its ~187-day span between themNOAA 1991–2020 Climate Normals
- The soil order, drainage, surface pH, and the 3 most extensive named soil series mapped in Bonner CountyUSDA NRCS SSURGO
- 627 documented contamination sites inside the county boundary, distance-sorted from its center — the closest Mining record about 1.3 miles outFederal environmental registers
- Bonner County's boundary and the 1,109,265 acres inside itUS Census TIGER/Line 2025
- Which of 1,086 plants clear zones 6b and a ~187-day seasonGrowable Ground crop-matching engine
- Bonner County sitting wholly inside the Northern RockiesUS EPA Level III Ecoregions
- Which agricultural compounds go onto Bonner County farmland, and roughly how muchUSGS NAWQA EPest county estimates
Inherited from a wider read
- The growing challenges every Idaho grower plans around — written at state scale, so they stay on the state guidefrom Idaho
What this page can’t tell you
- How the season shifts across Bonner County — the ~187 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 Bonner County's 1,109,265 acreswhy one lot differs from the next →
- Which of those 627 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 Bonner Countyread your own land →