Boise County, in Idaho, sits in USDA hardiness zone 6b — a range where zone-matched perennials and frost-aware annual timing set what succeeds.
Well-matched crops include cabbage, blackberry, california poppy, and collard greens, and the gap between "grows in the area" and "grows in your yard" is closed by soil, sun, and drainage.
Boise County lies within the Treasure Valley — a regional growing area with its own character.
Grounded in USDA PHZM 2023 · Growable Ground suitability scoring · NOAA 1991–2020 Climate Normals
Boise County holds more than one microclimate.
Soils and elevations shift across Boise 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 Boise County — soil, climate, flood, and parcel records. How we handle your address.
No card required · your full report in seconds
Boise County — the short answer
Boise County, Idaho: USDA zone 6b, about 125 days between hard freezes, across 1.2M acres.
- USDA zone
- 6b
- USDA PHZM 2023
- Last hard freeze (28°F)
- May 30
- NOAA 1991–2020 Climate Normals, 28°F
- First hard freeze (28°F)
- Oct 2
- NOAA 1991–2020 Climate Normals, 28°F
- Days between freezes
- ~125
- NOAA 1991–2020 Climate Normals, 28°F
- County area
- 1.2M 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 Boise County's average, not your lot's — a low corner or a tree line moves it. Against Boise County's 125-day season, see what your own ground reads.
Heat in Boise County
Across a year, Boise County accumulates about 1,004 growing degree days above 50°F, about 487 fewer than the middle Idaho county — ahead of 6 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 Boise County
Across Boise County, the ground is predominantly Mollisols, where Shirts, Charters, and Coski are the most extensive named soil series. The soil is generally somewhat excessively drained with a fine gravelly sandy loam surface. Topsoil pH runs about 5.9–6.5, slightly acidic. Rainfall drains through hydrologic group A soils.
Soil order
Mollisols
Drainage
Somewhat excessively drained
Hydric soils
0%
Soil still varies lot by lot — soil types explained.
How the ground varies across Boise County
The USDA soil survey maps 45% of Boise County as somewhat excessively drained — but another 53% drains differently: 38% well drained, 14% excessively drained.
Shirts is the most extensive named soil at 9% of mapped acres, then Charters (7%) and Coski (5%).
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 Boise County
Each reading below is measured for Boise 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 Boise County are somewhat excessively drained, in hydrologic group A — 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 Boise County runs about pH 5.9–6.5, 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
MeasuredBoise County runs about 125 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
MeasuredBoise 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 Boise County is in
Boise County sits in the Idaho Batholith — EPA Level III, inside the wider Northwestern Forested Mountains. One consistent ecological setting across the whole county.
What Grows in Boise County
We scored all 1,086 plants against Boise County's own USDA zone 6b and its own 125-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 Boise County?
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 May 2; tender transplants wait until two to three weeks after the last 28°F hard freeze, which lands near May 30 (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 gets applied to farmland in Boise County
USGS estimates 3,533 lb of Glyphosate on Boise County farmland in 2019, its largest by weight, ahead of Chlorpyrifos (638 lb) and 2,4-d (546 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 Boise County — and how to grow with it.
We checked the federal record across Boise County — 276 documented sites across 6 of the 9 source types we track.
The most significant on record: 4 Superfund sites (none NPL-listed). Sites tracked in EPA's Superfund program — from assessment-stage CERCLIS entries to confirmed National Priorities List cleanup sites.
Boise 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 Boise County
Closest first, across Boise County. Listing isn't leaking, and distance isn't exposure.
- Idaho CityMining · 0.6 mi
- Church Placer MineMining · 0.6 mi
- Mammoth MineMining · 1.3 mi
- Golden Cycle MineMining · 3.1 mi
- Black Jack ProspectMining · 3.5 mi
- Sarvis ProspectMining · 3.8 mi
- Edna MineMining · 3.8 mi
- Overlook MineMining · 4.4 mi
- Cumo ProspectMining · 4.8 mi
- VoltaireMining · 4.9 mi
- Enterprise Group MineMining · 5.2 mi
- Ader GroupMining · 5.2 mi
6 more sites are on the record inside the same radius. See them on the map
Measured from Boise 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 Boise County.
Sources Checked
across Boise County
Severity Distribution
across Boise County
Highest-Severity Sites
A note from Gnorman
What an experienced grower watches for around here
In and around Boise County, two things run higher than the national average across Boise County — Mining (186 sites) and Superfund (4 sites). That's not a problem with your land — it's information about 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.
Superfund: Superfund sites represent the most severe contamination in the federal system.
Test soil for heavy metals (lead, arsenic, cadmium, mercury) — this is essential near any mining site.
Commission professional soil testing before any food production (test for heavy metals, VOCs, and SVOCs).
Check your specific parcel in Boise 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 Boise County average
Your land is one point inside Boise County
Everything above resolves to Boise County as a whole — one PHZM band and one county frost record, read across 1.2M 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 Boise County Average
Boise County Average
- ●USDA Zones 6b, averaged across Boise County
- ●One soil character for all of Boise County
- ●Frost dates read at Boise County's scale: May 30 to Oct 2
YOUR Parcel
- ✓Your exact zone, not Boise County's 6b
- ✓Your SSURGO soil type & pH
- ✓Your sun exposure, cast in 3D
See MY Growing Report
Read your parcel in Boise County
Pull a site-specific report for your exact address in Boise County, Idaho — soil, sun, drainage, frost risk, and scored plant recommendations.
Three things about your lot that Boise County averages can't show:
We read public map data around Boise County — soil, climate, flood, and parcel records. How we handle your address.
25+ data sources read at your address, not the Boise County average
How we know this about Boise 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 Boise County carries no record of its own, the figure is inherited and labelled — the resolution ledger below names each.
Common questions about Boise County
When does frost risk typically end in Boise County?
The last hard freeze (28°F) in Boise County typically lands around May 30, 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 20.
How long is the growing season in Boise County?
Measured between 28°F hard freezes, Boise County sees about 125 frost-free days — roughly May 30 through Oct 2, per NOAA 1991–2020 climate normals. Tender crops work a shorter one: nearer Jun 20 to Sep 18, about 90 days.
Is the soil safe to grow vegetables in Boise County?
The federal record around Boise County runs heavier than most — 276 documented sites, mostly Mining entries (186), the nearest Mining record about 0.6 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 Boise County?
With about 125 frost-free days between hard freezes, Boise County 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 153 to 181 days — and cold frames or low tunnels buy more. Starting transplants indoors ahead of the May 30 hard-freeze normal stretches the season without touching the calendar.
Everything above is measured at Boise County's scale — its 6b band and its 125-day season. Your yard writes its own version of Boise 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 Boise County’s own scale
8 of the readings below were taken at Boise County's own scale — its own ~125-day span between 28°F freezes, the 3 most extensive soil series mapped here and 276 documented sites inside its boundary; one is borrowed from a wider read, named and linked below.
Measured here
- Boise County's own USDA hardiness band, zones 6bUSDA PHZM 2023
- Boise County's own 28°F hard-freeze dates and its ~125-day span between themNOAA 1991–2020 Climate Normals
- The soil order, drainage, surface pH, and the 3 most extensive named soil series mapped in Boise CountyUSDA NRCS SSURGO
- 276 documented contamination sites inside the county boundary, distance-sorted from its center — the closest Mining record about 0.6 miles outFederal environmental registers
- Boise County's boundary and the 1,215,594 acres inside itUS Census TIGER/Line 2025
- Which of 1,086 plants clear zones 6b and a ~125-day seasonGrowable Ground crop-matching engine
- Boise County sitting wholly inside the Idaho BatholithUS EPA Level III Ecoregions
- Which agricultural compounds go onto Boise 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 Boise County — the ~125 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 Boise County's 1,215,594 acreswhy one lot differs from the next →
- Which of those 276 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 Boise Countyread your own land →