Generally — Most Areas
boxwood (zones 5-8) suits most of Utah (4a-9a) — zones 5-8 are in range, and the rest of the state is the exception.
Boxwood in Utah — the short answer
Boxwood in Utah: hardy in zones 5–8, against a state median of ~175 frost-free days.
- Plant zones
- 5-8
- Manual horticultural correction (source not retained); NC State Extension and Missouri Botanical Garden, with the remaining rows from other published sources or Growable Ground compilation
- Utah zones
- 4a-9a
- USDA PHZM 2023
- Frost window
- Apr 12 - May 6 – Oct 8 - Oct 27
- NOAA RCC ACIS 1991-2020, 28°F
- Shortest county season
- 98 days
- NOAA Regional Climate Centers ACIS, 1991-2020, county 28°F killing freeze
Plant data: Growable Ground Plant Database, compiled from FAO ECOCROP, USDA PLANTS and university Extension sources — per-field provenance varies and is published with the dataset.
Your yard isn't the whole zone.
Utah spans zones 4a-9a, but your yard sits in exactly one — and slope, tree cover, and cold-air pockets nudge it further. Enter your address and we'll score boxwood against your parcel's actual hardiness, soil, and sun.
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Utah is not one climate
Utah’s winter-low ladder runs across 29 counties, from zone 4.5 in Rich County to zone 7.5 in Washington County. That is 30°F between the two counties’ average coldest night — the difference between boxwood overwintering in the ground and coming under cover.
The middle half of 29 counties runs 6–7 zones, with a median of 6.5 zones — a 3-zone span end to end.
Measured across 29 Utah counties. USDA PHZM 2023, per county. Quartiles are order statistics — every figure shown is a value a real county recorded, not an interpolation. Your own site sits somewhere inside this range; a parcel report resolves where.
Where in Utah Fits Best
Boxwood is rated for zones 5–8 — a cold floor USDA puts at -20 to -10°F. Against Utah’s 29 counties that band holds in 28 of them, and the line runs at Daggett County (zone 5b), the coldest county still inside it.
Inside zones 5–8
28 counties
- Iron County · zone 5b
- Sanpete County · zone 5b
- Summit County · zone 5b
3 of 28 shown
Below the zone 5 floor
1 county
- Rich County · zone 4b
Winter cold is the limit here — the same plant works in a container that comes under cover.
County hardiness zones: USDA Plant Hardiness Zone Map (PHZM) 2023, per county. A zone is a 10°F band of average annual extreme minimum temperature, so the floor above is the band the plant's rating denotes, not a single measured kill point. Slope, shelter and cold-air drainage routinely move a site half a zone either way from its county figure — which is the part only your address resolves.
Even within Utah's zones 4a-9a, county microclimates differ enough to change what thrives. These counties carry the closest zone match for boxwood (USDA PHZM 2023):
Zone Comparison
Boxwood Needs
- USDA Zones: 5-8
- Mature size: 15 ft tall
- Drought tolerance: Medium
Utah Has
- USDA Zones: 4a-9a
- Last Hard Freeze (28°F): Apr 12 - May 6
- First Hard Freeze (28°F): Oct 8 - Oct 27
- Annual Rainfall: 5-20 inches
- Common Soils: Sandy loam, Alkaline clay, Desert sand
Plant Zone Range (zones 5-8)
Preferred Soil pH
Plant data: Growable Ground Plant Database, compiled from FAO ECOCROP, USDA PLANTS, and university Extension sources — per-field provenance varies and is published with the dataset. State data: USDA ARS PHZM 2023, NOAA Climate Normals, NRCS SSURGO.
When to Plant Boxwood in Utah
The frost window
Across Utah, the last spring hard freeze (28°F) clears between Apr 12 and May 6, and the first fall hard freeze lands between Oct 8 and Oct 27 (NOAA Regional Climate Centers ACIS, 1991-2020). Counting from the latest last freeze to the earliest first freeze, that's a 155-day window you can count on — up to 198 days on a mild site in a kind year. That marks the hard freeze, not the last light frost, so tender transplants usually wait another 2-3 weeks.
Winter standing
Utah runs as cold as USDA zone 4, and no sourced winter-hardiness floor is on record for boxwood, so this page does not state whether it overwinters here — and gives no fall establishment date on the strength of a guess. Whether boxwood is a permanent planting or a replant-every-spring crop for you turns on your own zone within Utah; check its hardiness range against that before treating it as long-lived ground.
Frost window: NOAA Climate Normals 1991-2020. Plant timing fields: Growable Ground Plant Database — frost-free days from FAO ECOCROP, days to harvest from university Extension production guides, and growing-degree-day and chill-hour minimums that are compilation estimates rather than published figures. Your site's own frost dates can run earlier or later than the state range — a parcel report pins them down.
Growing Season Fit
The zone check says boxwood survives winter in part of Utah, not across all of it. Whether the season is long enough — and warm enough — is a different question.
Chill hours
Boxwood requires ~200 chill hours (32-45°F dormancy window). Utah typically banks ~2500 chill hours per winter (from PRISM 1991-2020 climate normals), which keeps this plant on track.
GDD and chill-hour figures are computed from PRISM 1991-2020 monthly climate normals; frost-free days from NOAA Regional Climate Centers ACIS, 1991-2020. Each is the state median across its counties (P25/P75 span the within-state spread). Hardiness-zone range is USDA PHZM 2023.
Soil + Drainage Fit
Boxwood likes near-neutral soil (pH 6.5-8.5). That's the common-ground band across Utah's sandy loam and alkaline clay — a soil test confirms it for your site. It will grow across that whole span, but it does best between pH 7 and 8 — worth knowing before you decide whether a Utah soil test result is a problem or just a number.
Plant pH requirements: FAO ECOCROP and USDA PLANTS, with the remaining rows from other published sources or Growable Ground compilation. Drainage: FAO ECOCROP, with the remaining rows from other published sources or Growable Ground compilation. Utah soil profile from USDA NRCS SSURGO. Site-specific verification: a 30-minute soil test from your local Extension lab.
What Else to Consider for Boxwood in Utah
Zone compatibility tells you about winter cold survival — but Utah growers also need to think about:
Very low rainfall — irrigation essential
Alkaline soils (pH 7.5-8.5) limit many species
High altitude frost risk in mountain valleys
What to actually do about these — and the constraints that apply to every Utah grower, not just boxwood — is covered on the Utah growing guide.
Where in Utah Boxwood Is Zone-Hardy
Boxwood is rated for USDA zones 5–8. 28 of Utah’s 29 counties fall inside that band. The coldest that does is Daggett County at zone 5b. 1 county sits below the plant’s zone 5 floor, where an unprotected plant is relying on snow cover and a mild year. Where you are in Utah decides this one.
Across those 29 counties Utah’s winter-low ladder runs from zone 4b in Rich County to zone 7b in Washington County — 3 USDA zones of spread, which is 30°F between the two counties’ average coldest night of the year. That is why a statewide hardiness answer is where you start and not where you finish.
The planting window moves with it. Summit County holds its last hard freeze (28°F) until about Jun 10, while Washington County is clear by Mar 20 — 82 days apart. Set boxwood out on your county’s date, not the state’s.
County hardiness zones: USDA Plant Hardiness Zone Map (PHZM) 2023, per county. County last-freeze dates: NOAA Regional Climate Centers ACIS (1991-2020), county 28°F killing freeze — earlier than the folk 32°F "last frost". Boxwood’s zone 5–8 band: USDA PLANTS / Growable Ground plant database. A parcel report resolves your address’s own zone and frost dates rather than its county’s.
Pollinator + Wildlife Value
Boxwood draws honeybees (low value, Growable Ground Plant Database). Planting it near vegetable beds can lift fruit set on neighboring crops. Outdoors, boxwood can only work that bloom inside Utah's frost window — roughly 175 days, opening after the last 28°F freeze (Apr 12 - May 6) and closing at the first (Oct 8 - Oct 27), per NOAA Regional Climate Centers ACIS, 1991-2020. Deer pressure is meaningful across much of Utah; boxwood is listed as deer-resistant (USDA PLANTS Database), which makes it a safer pick for unfenced sites. Our deer & wildlife guide carries the full deer-resistant list and how to protect the rest.
Utah Cooperative Extension
For Utah-specific cultivar recommendations, planting calendars, and pest pressure for boxwood, the canonical source is Utah State University Extension. Their fact sheets carry the local trial data we can't generalize across 50 states.
Is Boxwood native to Utah?
No — the USDA PLANTS Database lists Boxwood as introduced rather than native in the Lower 48, so it is not part of Utah's native flora. It grows here as a garden plant; pairing it with a few Utah natives keeps local pollinators fed too.
Looking for plants that belong here? The Utah growing guide lists USDA-documented natives for the state.
Native-range data: USDA PLANTS Database state-distribution records, accessed 2026-07-01.
Common Questions About Growing Boxwood in Utah
When can I plant Boxwood in Utah?
Utah's last spring hard freeze (28°F) clears between Apr 12 and May 6, and the first fall hard freeze lands between Oct 8 and Oct 27 (NOAA Regional Climate Centers ACIS, 1991-2020). No sourced winter-hardiness floor is on record for Boxwood, so this page does not state whether it overwinters in Utah and publishes no fall establishment date for it — check its hardiness range against your own zone before treating it as a permanent planting.
What hardiness zone is Boxwood grown in across Utah?
Utah spans USDA hardiness zones 4a-9a (USDA ARS PHZM 2023). Boxwood carries a range of zones 5-8, so the overlap zones are where outdoor growing is most reliable.
How many frost-free days does a typical Utah site have?
A typical Utah site sees ~175 frost-free days per year (derived from NOAA Regional Climate Centers ACIS, 1991-2020). Boxwood should be matched against that window, so check whether your local microclimate runs above or below the state average before settling on a planting date.
Is Boxwood native to Utah?
No — the USDA PLANTS Database lists Boxwood as introduced rather than native in the Lower 48, so it is not part of Utah's native flora. It grows here as a garden plant; pairing it with a few Utah natives keeps local pollinators fed too.
How should I amend the soil for Boxwood in Utah?
Boxwood prefers pH 6.5-8.5 (FAO ECOCROP). That sits in the common-ground band across Utah soils — a 30-minute soil test from a local Extension lab confirms it for your specific site.
Will Boxwood actually grow on my specific land in Utah?
State-level zone + climate data is a sketch. A Growable Ground parcel report scores boxwood against your address's exact soil pH, drainage, sun, and frost-date data drawn from USDA SSURGO, NOAA, and PRISM — not state averages.
Check your specific parcel in Utah
State-level data is a sketch. Your Growable Ground report scores boxwood against your parcel's exact soil, sun, drainage, and frost data — not zone averages.
Three things about your lot that Utah boxwood averages can't show:
We read public map data around Utah — soil, climate, flood, and parcel records. How we handle your address.
25+ data sources read at your address, not the Utah boxwood average
Explore More
Growing guides for boxwood
Explore Utah county by county
Utah carries 29 counties with their own USDA zone — a sample of the growing pages for boxwood there:
Where else boxwood grows
Boxwood's zone band crosses state lines — these are the states closest to Utah in winter climate where it also has a page, plus the far ends of its range. Each one re-answers the question with that state's own record.
More to grow in Utah
Utah has a growing page for 1,038 plants — a rotating sample of the rest of the shelf.
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