Koosharem, Utah, sits in USDA hardiness zone 5b — a band that supports both cool-season staples and warm-season crops chosen to fit the local frost window.
Growers here do well with pumpkin, blackberry, lavender, and zucchini — with the usual caveat that any single yard's soil, sun, and drainage cast the deciding vote.
Even in Koosharem, 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 Koosharem 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 Koosharem — soil, climate, flood, and parcel records. How we handle your address.
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Koosharem — the short answer
Koosharem, Utah: USDA zone 5b, about 107 days between hard freezes, across 534 acres of town.
- USDA zone
- 5b
- 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
- Town area
- 534 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 5b is Koosharem's average, not your lot's — a low corner or a tree line moves it. Against Koosharem's 107-day season, see what your own ground reads.
Soil varies lot by lot — soil types explained.
What this means for growing in Koosharem
Each reading below is measured for Koosharem itself — here is what it means for a garden here, and the move an experienced grower makes about it.
Season length
MeasuredKoosharem 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
MeasuredKoosharem sits in USDA hardiness zone 5b.
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 Koosharem is in
Koosharem sits in the Wasatch and Uinta Mountains — EPA Level III, inside the wider Northwestern Forested Mountains. That is read at Koosharem's own centroid rather than borrowed from Sevier County.
What Grows in Koosharem
Every plant below cleared Koosharem's own zone 5b and its 107-day season. Each card opens that plant's Utah profile. How we score.
Is it too late to plant in Koosharem?
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. When the window is tight, the fall moves are quick ones — baby greens, radishes, and garlic set for next season.
What's on the federal record near Koosharem
Closest first, within ~10 miles of Koosharem. Listing isn't leaking, and distance isn't exposure.
- UDOT STA. #331Underground Storage Tanks · 400 ft
- CHARLES DELANGEUnderground Storage Tanks · 1200 ft
- (C-26- 1)23ddb- 1Nitrate · 1.1 mi
- GRASS VALLEY RANCHUnderground Storage Tanks · 1.3 mi
- (C-27- 1)10dab- 1Nitrate · 2.6 mi
- (C-26- 1)12dbc- 1Nitrate · 3.5 mi
- BILL SORENSON PROPERTYUnderground Storage Tanks · 4.9 mi
- FULLMER CEDAR RIDGE DAIRYCAFO · 6.5 mi
- RICHFIELD CITYPFAS · 6.9 mi
- LAKESIDE RESORTUnderground Storage Tanks · 7.9 mi
- FISHLAKE LODGEUnderground Storage Tanks · 8.9 mi
- FISHLAKE ADMINISTRATIVE SITEUnderground Storage Tanks · 9.0 mi
Measured from Koosharem'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 Koosharem.
Total Sites
16
within ~10 miles of Koosharem
Risk Level
Moderate
Highest-severity
1 concentrated animal feeding operation
Sources Checked
within ~10 miles of Koosharem
Severity Distribution
within ~10 miles of Koosharem
Highest-Severity Sites
Know Before You Grow
- •Underground tanks leak petroleum as they age — near a former filling station, test the soil.
- •On a private well, test for nitrates: above 10 mg/L the water needs treatment before irrigating.
- •Large animal operations push nitrates and bacteria downstream. Below one, test your water.
Check your specific parcel in Koosharem
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 Koosharem average
Your land is one point inside Koosharem
Everything above resolves to Koosharem as a whole — one PHZM band and one 28°F frost record, read across 534 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 town 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 Koosharem Average
Koosharem Average
- ●USDA Zones 5b, averaged across Koosharem
- ●One soil character for all of Koosharem
- ●Frost dates read at Koosharem's scale: Jun 2 to Sep 17
YOUR Parcel
- ✓Your exact zone, not Koosharem's 5b
- ✓Your SSURGO soil type & pH
- ✓Your sun exposure, cast in 3D
See MY Growing Report
Read your specific parcel in Koosharem
Pull a site-specific report for your exact address in Koosharem, Utah — soil, sun, drainage, frost risk, and scored plant recommendations.
Three things about your lot that Koosharem averages can't show:
We read public map data around Koosharem — soil, climate, flood, and parcel records. How we handle your address.
25+ data sources read at your address, not the Koosharem average
How we know this about Koosharem
The datasets: hardiness from the USDA ARS Plant Hardiness Zone Map 2023, read at this town’s own centroid; hard-freeze dates from NOAA 1991–2020 28°F normals at Koosharem’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 town grain anywhere on this page — there is no town-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 Koosharem
When does frost risk typically end in Koosharem?
The last hard freeze (28°F) in Koosharem 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 Koosharem?
The first hard freeze (28°F) in Koosharem 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 Koosharem?
Measured between 28°F hard freezes, Koosharem 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 Koosharem?
The federal record around Koosharem shows 16 documented sites, mostly Underground Storage Tanks entries (8), 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 gardeners stretch the season in Koosharem?
With about 107 frost-free days between hard freezes, Koosharem 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 Koosharem's scale — its 5b band and its 107-day season. Your yard writes its own version of Koosharem'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 Koosharem’s own scale
6 of the readings below were taken at Koosharem's own scale — its own ~107-day season between 28°F freezes, the 534 acres it covers and 16 documented sites around it; 4 are borrowed from a wider read, named and linked below.
Measured here
- Koosharem's own USDA hardiness band, zones 5bUSDA PHZM 2023
- Koosharem's own 28°F hard-freeze dates, about Jun 2 and Sep 17 and the ~107-day span between themNOAA 1991–2020 Climate Normals
- 16 documented contamination sites on the federal record near Koosharem, the closest Underground Storage Tanks record under a tenth of a mile out from the town centreFederal environmental registers
- Koosharem's boundary and the 534 acres inside itUS Census TIGER/Line 2025
- Which of 1,086 plants clear zones 5b and a ~107-day seasonGrowable Ground crop-matching engine
- The ecoregion at Koosharem's own centroid, the Wasatch and Uinta MountainsUS EPA Level III Ecoregions
Inherited from a wider read
- Soil character — no town-scale survey exists, so Koosharem's 534 acres read through its county's SSURGO summaryfrom Sevier County
- Growing-degree days and winter chill — measured county-wide only, so the county page carries themfrom Sevier County
- The growing challenges every Utah grower plans around — written at state scale, so they stay on the state guidefrom Utah
- Butterfly and beetle records, and the farmland pesticide estimate — all published county-widefrom Sevier County
What this page can’t tell you
- The soil pH, drainage, sun hours, and frost pockets on any one lot among Koosharem's 534 acreswhy one lot differs from the next →
- Which side of Koosharem you're on — a low spot frosts first and a south wall warms early, and one normal is being asked to speak for all 534 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 Koosharem-wide figureread your own land →
More in Utah
Wider growing context
What grows across UtahKoosharem sits outside our named growing regions, so Utah as a whole is its closest context here.
Nearby growing guides