Swan Valley, Idaho, sits in USDA hardiness zone 5a — enough range to grow cool-season vegetables, hardy fruit, and warm-season crops that mature before the first hard frost.
A short list that earns its place here — cabbage, cranberry, lavender, and collard greens — with any one site's soil, sun, and drainage making the final cut.
Even in Swan Valley, 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 Swan Valley 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 Swan Valley — soil, climate, flood, and parcel records. How we handle your address.
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Swan Valley — the short answer
Swan Valley, Idaho: USDA zone 5a, about 137 days between hard freezes, across 7K acres of city.
- USDA zone
- 5a
- USDA PHZM 2023
- Last hard freeze (28°F)
- May 12
- NOAA 1991–2020 Climate Normals, 28°F — this town
- First hard freeze (28°F)
- Sep 26
- NOAA 1991–2020 Climate Normals, 28°F — this town
- Days between freezes
- ~137
- NOAA 1991–2020 Climate Normals, 28°F — this town
- City area
- 7K 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 Swan Valley's average, not your lot's — a low corner or a tree line moves it. Against Swan Valley's 137-day season, see what your own ground reads.
Soil varies lot by lot — soil types explained.
What this means for growing in Swan Valley
Each reading below is measured for Swan Valley itself — here is what it means for a garden here, and the move an experienced grower makes about it.
Season length
MeasuredSwan Valley runs about 137 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
MeasuredSwan Valley 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 Swan Valley is in
Swan Valley sits in the Middle Rockies — EPA Level III, inside the wider Northwestern Forested Mountains. That is read at Swan Valley's own centroid rather than borrowed from Bonneville County.
What Grows in Swan Valley
Every plant below cleared Swan Valley's own zone 5a and its 137-day season. Each card opens that plant's Idaho profile. How we score.
Is it too late to plant in Swan Valley?
Almost never — the real question is what to plant next. Cool-season crops can go in from around Apr 14; tender transplants wait until two to three weeks after the last 28°F hard freeze, which lands near May 12 (NOAA 1991–2020 climate normals); and from midsummer, planting counts back from the first fall freeze around Sep 26 — 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's on the federal record near Swan Valley
Closest first, within ~10 miles of Swan Valley. Listing isn't leaking, and distance isn't exposure.
- 01N 43E 12ACB1Nitrate · 0.9 mi
- 01N 43E 12ACD1Nitrate · 0.9 mi
- RAINEY CREEK COUNTRY STOREUnderground Storage Tanks · 0.9 mi
- Targhee National Forest Snake River Work StationUnderground Storage Tanks · 1.0 mi
- BONNEVILLE COUNTY 3Underground Storage Tanks · 1.0 mi
- 01N 44E 05CCD1Nitrate · 1.0 mi
- 02N 43E 35DAD1Nitrate · 1.6 mi
- CARL ZITLAU 1Underground Storage Tanks · 1.7 mi
- 01N 44E 17ADA1Nitrate · 2.7 mi
- IRWIN TRADING POSTUnderground Storage Tanks · 3.0 mi
- SWAN VALLEY ELEMENTARY SCHOOLUnderground Storage Tanks · 3.0 mi
- PALISADES RDUnderground Storage Tanks · 3.7 mi
6 more sites are on the record inside the same radius. See them on the map
Measured from Swan Valley'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 Swan Valley.
Total Sites
29
within ~10 miles of Swan Valley
Risk Level
Elevated
Highest-severity
1 Superfund site (none NPL-listed)
Sources Checked
within ~10 miles of Swan Valley
Severity Distribution
within ~10 miles of Swan Valley
Highest-Severity Sites
A note from Gnorman
What an experienced grower watches for around here
In and around Swan Valley, Nitrate runs higher than the national average — 14 sites within ~10 miles of Swan Valley. 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.
Test well water for nitrate if you rely on a private well for irrigation (EPA standard: 10 mg/L).
Check your specific parcel in Swan Valley
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 Swan Valley average
Your land is one point inside Swan Valley
Everything above resolves to Swan Valley as a whole — one PHZM band and one 28°F frost record, read across 7K 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 Swan Valley Average
Swan Valley Average
- ●USDA Zones 5a, averaged across Swan Valley
- ●One soil character for all of Swan Valley
- ●Frost dates read at Swan Valley's scale: May 12 to Sep 26
YOUR Parcel
- ✓Your exact zone, not Swan Valley's 5a
- ✓Your SSURGO soil type & pH
- ✓Your sun exposure, cast in 3D
See MY Growing Report
Read your specific parcel in Swan Valley
Pull a site-specific report for your exact address in Swan Valley, Idaho — soil, sun, drainage, frost risk, and scored plant recommendations.
Three things about your lot that Swan Valley averages can't show:
We read public map data around Swan Valley — soil, climate, flood, and parcel records. How we handle your address.
25+ data sources read at your address, not the Swan Valley average
How we know this about Swan Valley
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 Swan Valley’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 Swan Valley
When does frost risk typically end in Swan Valley?
The last hard freeze (28°F) in Swan Valley typically lands around May 12, 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 2.
When is the first frost in Swan Valley?
The first hard freeze (28°F) in Swan Valley typically arrives around Sep 26, per NOAA 1991–2020 climate normals — the point tender summer crops finish. Lighter frosts run ahead of it, near Sep 12, so the watching starts about Aug 27 — about 137 days after the spring freeze cleared.
How long is the growing season in Swan Valley?
Measured between 28°F hard freezes, Swan Valley sees about 137 frost-free days — roughly May 12 through Sep 26, per NOAA 1991–2020 climate normals. Tender crops work a shorter one: nearer Jun 2 to Sep 12, about 102 days.
Is the soil safe to grow vegetables in Swan Valley?
The federal record around Swan Valley is a meaningful one — 29 documented sites, mostly Nitrate entries (14), the nearest Nitrate record about 0.9 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 Swan Valley?
With about 137 frost-free days between hard freezes, Swan Valley 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 165 to 193 days — and cold frames or low tunnels buy more. Starting transplants indoors ahead of the May 12 hard-freeze normal stretches the season without touching the calendar.
Everything above is measured at Swan Valley's scale — its 5a band and its 137-day season. Your yard writes its own version of Swan Valley'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 Swan Valley’s own scale
6 of the readings below were taken at Swan Valley's own scale — its own ~137-day season between 28°F freezes, the 7,428 acres it covers and 29 documented sites around it; 4 are borrowed from a wider read, named and linked below.
Measured here
- Swan Valley's own USDA hardiness band, zones 5aUSDA PHZM 2023
- Swan Valley's own 28°F hard-freeze dates, about May 12 and Sep 26 and the ~137-day span between themNOAA 1991–2020 Climate Normals
- 29 documented contamination sites on the federal record near Swan Valley, the closest Nitrate record about 0.9 miles out from the town centreFederal environmental registers
- Swan Valley's boundary and the 7,428 acres inside itUS Census TIGER/Line 2025
- Which of 1,086 plants clear zones 5a and a ~137-day seasonGrowable Ground crop-matching engine
- The ecoregion at Swan Valley's own centroid, the Middle RockiesUS EPA Level III Ecoregions
Inherited from a wider read
- Soil character — no town-scale survey exists, so Swan Valley's 7,428 acres read through its county's SSURGO summaryfrom Bonneville County
- Growing-degree days and winter chill — measured county-wide only, so the county page carries themfrom Bonneville 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 Bonneville County
What this page can’t tell you
- The soil pH, drainage, sun hours, and frost pockets on any one lot among Swan Valley's 7,428 acreswhy one lot differs from the next →
- Which side of Swan Valley you're on — a low spot frosts first and a south wall warms early, and one normal is being asked to speak for all 7,428 acresreading your own microclimate →
- How close that record sits to YOUR lot — the closest Nitrate record about 0.9 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 Swan Valley-wide figureread your own land →