Unlikely — Zone Mismatch
rose gum (zones 9-11) does not overlap with Idaho's zone range (3b-8a). Growing outdoors is unlikely without significant protection.
2 zones short — what would close it
Rose Gum is hardy to zone 9, and the warmest ground in Idaho is zone 7 — 2 zones short. Planted in open ground it will not survive a Idaho winter. To grow it here, grow rose gum under glass — a greenhouse is the only lift this wide the engine models.
A greenhouse is the lift this needs. How a greenhouse changes what you can grow →
Zone math from 9-11 (plant) against 4-7 (Idaho). Lift modeled by crop_engine Sprint 20B effective_zone_modifier (+2 zones) via api/fast_sections.py Unlock Engine v2.
Your yard isn't the whole zone.
Idaho spans zones 3b-8a, 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 rose gum against your parcel's actual hardiness, soil, and sun.
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Zone Comparison
Rose Gum Needs
- USDA Zones: 9-11
- Frost-Free Days: 150+
- Sun: Full Sun
Idaho Has
- USDA Zones: 3b-8a
- Last Hard Freeze (28°F): Apr 26 - May 17
- First Hard Freeze (28°F): Oct 1 - Oct 17
- Annual Rainfall: 8-35 inches
- Common Soils: Volcanic ash, Silt loam, Sandy loam
Plant Zone Range (zones 9-11)
Preferred Soil pH
Plant data: USDA PLANTS Database / Growable Ground plant catalog. State data: USDA ARS PHZM 2023, NOAA Climate Normals, NRCS SSURGO.
When to Plant Rose Gum in Idaho
The frost window
Across Idaho, the last spring hard freeze (28°F) clears between Apr 26 and May 17, and the first fall hard freeze lands between Oct 1 and Oct 17 (NOAA Regional Climate Centers ACIS, 1991-2020). Counting from the latest last freeze to the earliest first freeze, that's a 137-day window you can count on — up to 174 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
Idaho runs as cold as USDA zone 3, and no sourced winter-hardiness floor is on record for rose gum, so this page does not state whether it overwinters here — and gives no fall establishment date on the strength of a guess. Whether rose gum is a permanent planting or a replant-every-spring crop for you turns on your own zone within Idaho; check its hardiness range against that before treating it as long-lived ground.
Timing tuned to sub-state frost dates — Valley County, not the statewide average.
Frost window: NOAA Climate Normals 1991-2020. Plant timing fields: USDA PLANTS Database. 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 rose gum does not survive a Idaho winter in the ground. The season figures below measure a different question — whether it could finish a season here at all — and they only bear on Idaho under protection.
Frost-free days
Rose Gum wants 150+ frost-free days; a typical Idaho site sees ~160 (NOAA Regional Climate Centers ACIS, 1991-2020). That leaves a tight window — use transplants and pick early-maturing cultivars.
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
Rose Gum likes near-neutral soil (pH 5-7.5). That's the common-ground band across Idaho's volcanic ash and silt loam — a soil test confirms it for your site. It will grow across that whole span, but it does best between pH 5.5 and 6.5 — worth knowing before you decide whether a Idaho soil test result is a problem or just a number. Drainage matters: this plant wants well (dry spells). If your Idaho site is heavier clay or sits in a low spot, raised beds or amendment with compost solve it.
Your land, not the state average
Idaho's soils run mostly silt loam, but SSURGO maps the series, texture, and drainage under your exact parcel. Rose Gum needs about 59 inches of workable depth, so it is that horizon — not the surface — you are testing for. That map unit, not the state average, decides how rose gum performs.
Check your parcel → Source: USDA NRCS SSURGO.
Plant pH and drainage requirements from USDA PLANTS Database. Idaho soil profile from USDA NRCS SSURGO. Site-specific verification: a 30-minute soil test from your local Extension lab.
Rose Gum in Idaho — Quick Answer
- Verdict: Unlikely — Zone Mismatch
- Plant Zones: 9-11 (USDA PLANTS Database)
- State Zones: 3b-8a (USDA ARS PHZM 2023)
- Growing Season: 28°F hard freezes about Apr 26 - May 17 to Oct 1 - Oct 17 (NOAA Regional Climate Centers ACIS, 1991-2020)
What Else to Consider for Rose Gum in Idaho
Zone compatibility tells you about winter cold survival — but Idaho growers also need to think about:
Short growing season at higher elevations
Arid conditions require irrigation in most of the state
Cold winter snaps can reach -30F in mountain valleys
Growing rose gum here specifically
Rose Gum needs pH 5.0–7.5; Idaho's dominant silt loam soils may or may not deliver that, so your parcel's SSURGO map unit is the real test.
Start with a soil test on your own ground and adjust pH and texture to fit rose gum's 5.0–7.5 range. How to handle it →
What to actually do about these — and the constraints that apply to every Idaho grower, not just rose gum — is covered on the Idaho growing guide.
Timing shifts within Idaho
Idaho isn't one climate. In Valley County, the last hard freeze (28°F) holds until about Jun 14 — roughly 42 days later than the recorded state median — so plant rose gum to your county's window, not the statewide date.
Rose Gum needs about 150 days of frost-free season to complete its cycle. 25 of Idaho’s 44 counties give it that outright. The tightest that does is Lewis County at 156 frost-free days — 6 to spare. Below that line you are transplanting or extending the season, not direct-sowing.
Across Idaho’s 44 counties the frost-free season runs from 94 days in Valley County to 216 days in Nez Perce County — a spread of 122 days, which is why a single statewide planting date misleads. The median Idaho county sees 160 frost-free days, leaving rose gum about 10 days of slack on a typical parcel — room for a second sowing where the season runs long.
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"). Rose Gum's 150-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
Rose Gum draws honeybees and native bees (high value, Growable Ground Plant Database). Planting it near vegetable beds can lift fruit set on neighboring crops. Outdoors, rose gum can only work that bloom inside Idaho's frost window — roughly 160 days, opening after the last 28°F freeze (Apr 26 - May 17) and closing at the first (Oct 1 - Oct 17), per NOAA Regional Climate Centers ACIS, 1991-2020.
Good to Know Before You Plant Rose Gum
Rose Gum is listed as toxic to dogs, cats (leaves) at a moderate level (ASPCA). Most listed plants only cause brief upset — a raised bed or a fenced corner usually keeps curious pets clear.
Idaho Cooperative Extension
For Idaho-specific cultivar recommendations, planting calendars, and pest pressure for rose gum, the canonical source is University of Idaho Extension. Their fact sheets carry the local trial data we can't generalize across 50 states.
Common Questions About Growing Rose Gum in Idaho
When can I plant Rose Gum in Idaho?
Idaho's last spring hard freeze (28°F) clears between Apr 26 and May 17, and the first fall hard freeze lands between Oct 1 and Oct 17 (NOAA Regional Climate Centers ACIS, 1991-2020). No sourced winter-hardiness floor is on record for Rose Gum, so this page does not state whether it overwinters in Idaho 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 Rose Gum grown in across Idaho?
Idaho spans USDA hardiness zones 3b-8a (USDA ARS PHZM 2023). Rose Gum carries a range of zones 9-11, so the overlap zones are where outdoor growing is most reliable.
How many frost-free days does a typical Idaho site have?
A typical Idaho site sees ~160 frost-free days per year (derived from NOAA Regional Climate Centers ACIS, 1991-2020). Rose Gum needs 150+ frost-free days, so check whether your local microclimate runs above or below the state average before settling on a planting date. In cooler counties like Valley, the freeze-free season runs shorter than the state average, so verify your own county's window.
How should I amend the soil for Rose Gum in Idaho?
Rose Gum prefers pH 5-7.5 and well (dry spells) drainage (FAO ECOCROP). That sits in the common-ground band across Idaho soils — a 30-minute soil test from a local Extension lab confirms it for your specific site.
Will Rose Gum actually grow on my specific land in Idaho?
State-level zone + climate data is a sketch. A Growable Ground parcel report scores rose gum 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 Idaho
State-level data is a sketch. Your Growable Ground report scores rose gum against your parcel's exact soil, sun, drainage, and frost data — not zone averages.
Three things about your lot that Idaho rose gum averages can't show:
We read public map data around Idaho — soil, climate, flood, and parcel records. How we handle your address.
25+ data sources read at your address, not the Idaho rose gum average
Explore More
Growing guides for rose gum
Analysis by the Growable Ground research team, grounded in USDA PLANTS, USDA NRCS SSURGO, NOAA Climate Normals (1991-2020), and named Cooperative Extension sources. How we know →
Cite this dataset
Kirchick, M. (2026). Growable Ground Plant Database [Data set]. Zenodo. https://doi.org/10.5281/zenodo.21435643
Licensed CC BY-NC 4.0. DOI 10.5281/zenodo.21435643
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