Generally — Most Areas
sweetspire (zones 5-11) suits most of Wyoming (3b-6a) — zones 5-6 are in range, and the rest of the state is the exception.
Sweetspire in Wyoming — the short answer
Sweetspire in Wyoming: hardy in zones 5–11, shade, against a state median of ~151 frost-free days.
- Plant zones
- 5-11
- 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
- Wyoming zones
- 3b-6a
- USDA PHZM 2023
- Frost window
- May 4 - May 13 – Sep 30 - Oct 7
- NOAA RCC ACIS 1991-2020, 28°F
- Shortest county season
- 79 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.
Wyoming spans zones 3b-6a, 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 sweetspire against your parcel's actual hardiness, soil, and sun.
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Wyoming is not one climate
Wyoming’s winter-low ladder runs across 23 counties, from zone 4.5 in Albany County to zone 5.5 in Uinta County. That is 10°F between the two counties’ average coldest night — the difference between sweetspire overwintering in the ground and coming under cover.
The middle half of 23 counties runs 4.5–5 zones, with a median of 5 zones — a 1-zone span end to end.
Measured across 23 Wyoming 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 Wyoming Fits Best
Sweetspire is rated for zones 5–11 — a cold floor USDA puts at -20 to -10°F. Against Wyoming’s 23 counties that band holds in 17 of them, and the line runs at Campbell County (zone 5a), the coldest county still inside it.
Inside zones 5–11
17 counties
- Carbon County · zone 5a
- Converse County · zone 5a
- Crook County · zone 5a
3 of 17 shown
Below the zone 5 floor
6 counties
- Albany County · zone 4b
- Big Horn County · zone 4b
- Hot Springs County · zone 4b
3 of 6 shown
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 Wyoming's zones 3b-6a, county microclimates differ enough to change what thrives. These counties carry the closest zone match for sweetspire (USDA PHZM 2023):
Zone Comparison
Sweetspire Needs
- USDA Zones: 5-11
- Frost-Free Days: 180+
- Sun: Shade
- Mature size: 6 ft tall
- Drought tolerance: Low
Wyoming Has
- USDA Zones: 3b-6a
- Last Hard Freeze (28°F): May 4 - May 13
- First Hard Freeze (28°F): Sep 30 - Oct 7
- Annual Rainfall: 6-20 inches
- Common Soils: Sandy loam, Clay, Alkaline
Plant Zone Range (zones 5-11)
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 Sweetspire in Wyoming
The frost window
Across Wyoming, the last spring hard freeze (28°F) clears between May 4 and May 13, and the first fall hard freeze lands between Sep 30 and Oct 7 (NOAA Regional Climate Centers ACIS, 1991-2020). Counting from the latest last freeze to the earliest first freeze, that's a 140-day window you can count on — up to 156 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
Wyoming runs as cold as USDA zone 3, and no sourced winter-hardiness floor is on record for sweetspire, so this page does not state whether it overwinters here — and gives no fall establishment date on the strength of a guess. Whether sweetspire is a permanent planting or a replant-every-spring crop for you turns on your own zone within Wyoming; 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 sweetspire survives winter in part of Wyoming, not across all of it. Whether the season is long enough — and warm enough — is a different question.
Frost-free days
Sweetspire wants 180+ frost-free days; a typical Wyoming site sees ~151 (NOAA Regional Climate Centers ACIS, 1991-2020) — 29 days short of what it needs. A typical Wyoming season does not carry this crop to harvest outdoors, and a gap that size is not one an earlier sowing date or a faster cultivar closes; growing it here means growing it under cover.
Chill hours
Sweetspire requires ~400 chill hours (32-45°F dormancy window). Wyoming 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
Sweetspire tolerates a wide pH range (pH 4-7.5) — 3.5 units, acid ground through alkaline — so soil acidity is rarely what limits it in Wyoming. A soil test is still worth having, but for what else it tells you about this site, not to clear this plant.
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. Wyoming soil profile from USDA NRCS SSURGO. Site-specific verification: a 30-minute soil test from your local Extension lab.
What Else to Consider for Sweetspire in Wyoming
Zone compatibility tells you about winter cold survival — but Wyoming growers also need to think about:
Extremely short growing season (60-90 frost-free days)
Very low rainfall requires irrigation
Persistent high winds desiccate and damage plants
What to actually do about these — and the constraints that apply to every Wyoming grower, not just sweetspire — is covered on the Wyoming growing guide.
Timing shifts within Wyoming
Sweetspire needs about 180 days of frost-free season to complete its cycle. No Wyoming county gives it that outdoors: even Big Horn County, the state’s longest season at 166 frost-free days, falls 14 days short — so it needs transplants, a short-season variety, or covered growing.
Across Wyoming’s 23 counties the frost-free season runs from 79 days in Teton County to 166 days in Big Horn County — a spread of 87 days, which is why a single statewide planting date misleads. The median Wyoming county sees 151 frost-free days, which is 29 days short of what sweetspire needs — so on a typical Wyoming parcel this is a transplant-or-protect crop, not a direct-sow one.
County last-freeze dates and frost-free day counts: NOAA Regional Climate Centers ACIS (1991-2020), county 28°F freeze (earlier than the folk 32°F "last frost"). Sweetspire's 180-day requirement: USDA PLANTS / Growable Ground plant database (minimum frost-free days). A parcel report resolves your address's own frost dates.
Pollinator + Wildlife Value
Sweetspire draws honeybees, native bees, and butterflies (moderate value, Growable Ground Plant Database). Planting it near vegetable beds can lift fruit set on neighboring crops. Outdoors, sweetspire can only work that bloom inside Wyoming's frost window — roughly 151 days, opening after the last 28°F freeze (May 4 - May 13) and closing at the first (Sep 30 - Oct 7), per NOAA Regional Climate Centers ACIS, 1991-2020.
Wyoming Cooperative Extension
For Wyoming-specific cultivar recommendations, planting calendars, and pest pressure for sweetspire, the canonical source is University of Wyoming Extension. Their fact sheets carry the local trial data we can't generalize across 50 states.
Is Sweetspire native to Wyoming?
Sweetspire is native to parts of the Lower 48, but the USDA PLANTS Database (accessed 2026-07-01) does not document a native range in Wyoming. It can still earn a place in a Wyoming garden — the zone comparison above tells you whether it will thrive.
Looking for plants that belong here? The Wyoming 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 Sweetspire in Wyoming
When can I plant Sweetspire in Wyoming?
Wyoming's last spring hard freeze (28°F) clears between May 4 and May 13, and the first fall hard freeze lands between Sep 30 and Oct 7 (NOAA Regional Climate Centers ACIS, 1991-2020). No sourced winter-hardiness floor is on record for Sweetspire, so this page does not state whether it overwinters in Wyoming 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 Sweetspire grown in across Wyoming?
Wyoming spans USDA hardiness zones 3b-6a (USDA ARS PHZM 2023). Sweetspire carries a range of zones 5-11, so the overlap zones are where outdoor growing is most reliable.
How many frost-free days does a typical Wyoming site have?
A typical Wyoming site sees ~151 frost-free days per year (derived from NOAA Regional Climate Centers ACIS, 1991-2020). Sweetspire needs 180+ frost-free days, so check whether your local microclimate runs above or below the state average before settling on a planting date.
Is Sweetspire native to Wyoming?
Sweetspire is native to parts of the Lower 48, but the USDA PLANTS Database (accessed 2026-07-01) does not document a native range in Wyoming. It can still earn a place in a Wyoming garden — the zone comparison above tells you whether it will thrive.
How should I amend the soil for Sweetspire in Wyoming?
Sweetspire tolerates pH 4-7.5 (USDA PLANTS). That is a 3.5-unit span, acid ground through alkaline, so pH is rarely what limits this plant on a Wyoming site — amend for drainage and organic matter first.
Will Sweetspire actually grow on my specific land in Wyoming?
State-level zone + climate data is a sketch. A Growable Ground parcel report scores sweetspire 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 Wyoming
State-level data is a sketch. Your Growable Ground report scores sweetspire against your parcel's exact soil, sun, drainage, and frost data — not zone averages.
Three things about your lot that Wyoming sweetspire averages can't show:
We read public map data around Wyoming — soil, climate, flood, and parcel records. How we handle your address.
25+ data sources read at your address, not the Wyoming sweetspire average
Explore More
Growing guides for sweetspire
Explore Wyoming county by county
Wyoming carries 23 counties with their own USDA zone — a sample of the growing pages for sweetspire there:
Where else sweetspire grows
Sweetspire's zone band crosses state lines — these are the states closest to Wyoming 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 Wyoming
Wyoming has a growing page for 806 plants — a rotating sample of the rest of the shelf.
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