Unlikely — Zone Mismatch
lobelia (zones 10-11) does not overlap with Utah's zone range (4a-9a). Growing outdoors is unlikely without significant protection.
One zone short — what would close it
Lobelia is hardy to zone 10, and the warmest ground in Utah is zone 9 — 1 zone short. Planted in open ground it will not survive a Utah winter. To grow it here, grow lobelia in a hoop house or unheated greenhouse — its modeled 1.5-zone lift covers this gap.
A hoop house or unheated greenhouse is the lift this needs. How a greenhouse changes what you can grow →
Zone math from 10-11 (plant) against 4-9 (Utah). Lift modeled by crop_engine.GREENHOUSE_ZONE_MODIFIER_BY_SUBTYPE['hoop_house'] (+1.5 zones) via api/fast_sections.py Unlock Engine v2.
Lobelia in Utah — the short answer
Lobelia in Utah: hardy in zones 10–11, part sun, against a state median of ~175 frost-free days.
- Plant zones
- 10-11
- 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
- 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
- Days to maturity
- 90 days
- Growable Ground Plant Database
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 lobelia against your parcel's actual hardiness, soil, and sun.
We read public map data for this spot — soil, climate, flood, and parcel records. How we handle your address.
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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 lobelia 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 Lobelia Stands in Utah
Lobelia is rated for zones 10–11 — a cold floor USDA puts at 30 to 40°F. No Utah county sits inside it, so in open ground this is a grown-under-cover plant here rather than a bed plant — which is a statement about Utah winters, not about lobelia.
Below the zone 10 floor
29 counties
- Rich County · zone 4b
- Daggett County · zone 5b
- Iron County · zone 5b
3 of 29 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.
Zone Comparison
Lobelia Needs
- USDA Zones: 10-11
- Sun: Part Sun
- Mature size: 6 in tall
- Picking window: ~90 days of harvest
- Drought tolerance: Low
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 10-11)
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 Lobelia 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.
When to start the seed
Those dates are when lobelia goes out, not when it starts. It is sown under cover about 10 weeks ahead, so counting back from Utah's late-side last freeze of May 6 is what fixes your sowing date — and a yard that clears frost earlier than the state's late date starts earlier still.
Winter standing
Utah runs as cold as USDA zone 4, and no sourced winter-hardiness floor is on record for lobelia, so this page does not state whether it overwinters here — and gives no fall establishment date on the strength of a guess. Whether lobelia 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.
Timing tuned to sub-state frost dates — Summit County, not the statewide average.
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 lobelia does not survive a Utah 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 Utah under protection.
Days to maturity
Lobelia matures in ~90 days (Growable Ground Plant Database). A typical Utah site has ~175 frost-free days, so plenty of room for a second succession.
Growing degree days
Lobelia needs ~700 GDD (base 50°F) to ripen. The state median runs ~2690 GDD (from PRISM 1991-2020 climate normals), so Utah's typical season clears that easily.
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
Lobelia likes near-neutral soil (pH 5.5-7). 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 5.8 and 6.5 — worth knowing before you decide whether a Utah soil test result is a problem or just a number. Drainage matters: this plant wants well (dry spells). If your Utah site is heavier clay or sits in a low spot, raised beds or amendment with compost solve it.
Your land, not the state average
Utah's soils run mostly loam, but SSURGO maps the series, texture, and drainage under your exact parcel. What matters for lobelia is the horizon its roots actually work, not the surface. That map unit, not the state average, decides how lobelia performs.
Check your parcel → Source: USDA NRCS SSURGO.
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 Lobelia 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
Growing lobelia here specifically
Lobelia wants pH 5.5–7.0 and rates to USDA zones 10–11, but Utah's soils are dominantly loam — the fit is decided by your parcel's own map unit, not the state average.
Match lobelia to your parcel's SSURGO map unit — test pH and texture, and amend toward its 5.5–7.0 range. How to handle it →
What to actually do about these — and the constraints that apply to every Utah grower, not just lobelia — is covered on the Utah growing guide.
Timing shifts within Utah
Utah isn't one climate. In Summit County, the last hard freeze (28°F) holds until about Jun 10 — roughly 45 days later than the recorded state median — so plant lobelia to your county's window, not the statewide date.
Lobelia needs about 90 days of frost-free season from planting to harvest. Even Summit County — Utah’s shortest season at 98 frost-free days — clears that by 8 days, so season length isn’t the constraint anywhere in Utah. What varies is your own parcel.
Across Utah’s 29 counties the frost-free season runs from 98 days in Summit County to 237 days in Washington County — a spread of 139 days, which is why a single statewide planting date misleads. The median Utah county sees 175 frost-free days, leaving lobelia about 85 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"). Lobelia's 90-day requirement: USDA PLANTS / Growable Ground plant database (days to maturity). A parcel report resolves your address's own frost dates.
Pollinator + Wildlife Value
Lobelia 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, lobelia 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.
Good to Know Before You Plant Lobelia
Lobelia is listed as toxic to dogs, cats (all) at a moderate level (ASPCA). Most listed plants only cause brief upset — a raised bed or a fenced corner usually keeps curious pets clear.
Recommended Lobelia Varieties for Utah
Utah publishes no state variety trial for lobelia, so we won't invent a "best for Utah" list. Choose types rated to your USDA hardiness zone (4a-9a), and confirm winter survival and drainage against your own parcel.
Utah Cooperative Extension
For Utah-specific cultivar recommendations, planting calendars, and pest pressure for lobelia, the canonical source is Utah State University Extension. Their fact sheets carry the local trial data we can't generalize across 50 states.
Is Lobelia native to Utah?
No — the USDA PLANTS Database lists Lobelia 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 Lobelia in Utah
When can I plant Lobelia 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 Lobelia, 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 Lobelia grown in across Utah?
Utah spans USDA hardiness zones 4a-9a (USDA ARS PHZM 2023). Lobelia carries a range of zones 10-11, 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). Lobelia 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. In cooler counties like Summit, the freeze-free season runs shorter than the state average, so verify your own county's window.
Is Lobelia native to Utah?
No — the USDA PLANTS Database lists Lobelia 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 Lobelia in Utah?
Lobelia prefers pH 5.5-7 and well (dry spells) drainage (Growable Ground Plant Database). 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 Lobelia actually grow on my specific land in Utah?
State-level zone + climate data is a sketch. A Growable Ground parcel report scores lobelia 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 lobelia against your parcel's exact soil, sun, drainage, and frost data — not zone averages.
Three things about your lot that Utah lobelia 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 lobelia average
Explore More
Growing guides for lobelia
Explore Utah county by county
Utah carries 29 counties with their own USDA zone — a sample of the growing pages for lobelia there:
Where else lobelia grows
Lobelia'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.
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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