Yes — Strong Match
mountain laurel (zones 5-11) covers every zone Illinois contains (5a-7b), so hardiness is not what limits it anywhere in the state.
Mountain Laurel in Illinois — the short answer
Mountain Laurel in Illinois: hardy in zones 5–11, shade, against a state median of ~212 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
- Illinois zones
- 5a-7b
- USDA PHZM 2023
- Frost window
- Mar 29 - Apr 8 – Oct 28 - Nov 5
- NOAA RCC ACIS 1991-2020, 28°F
- Shortest county season
- 177 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.
Illinois spans zones 5a-7b, 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 mountain laurel 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.
No card required · your full report in seconds
Illinois is not one climate
Illinois’s winter-low ladder runs across 102 counties, from zone 5 in Carroll County to zone 7 in Williamson County. That is 20°F between the two counties’ average coldest night — the difference between mountain laurel overwintering in the ground and coming under cover.
The middle half of 102 counties runs 5.5–6.5 zones, with a median of 6 zones — a 2-zone span end to end.
Measured across 102 Illinois 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 Illinois Fits Best
Even within Illinois's zones 5a-7b, county microclimates differ enough to change what thrives. These counties carry the closest zone match for mountain laurel (USDA PHZM 2023):
Zone Comparison
Mountain Laurel Needs
- USDA Zones: 5-11
- Frost-Free Days: 150+
- Sun: Shade
- Mature size: 10 ft tall
- Drought tolerance: High
Illinois Has
- USDA Zones: 5a-7b
- Last Hard Freeze (28°F): Mar 29 - Apr 8
- First Hard Freeze (28°F): Oct 28 - Nov 5
- Annual Rainfall: 34-48 inches
- Common Soils: Prairie loam, Silt loam, Clay loam
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 Mountain Laurel in Illinois
The frost window
Across Illinois, the last spring hard freeze (28°F) clears between Mar 29 and Apr 8, and the first fall hard freeze lands between Oct 28 and Nov 5 (NOAA Regional Climate Centers ACIS, 1991-2020). Counting from the latest last freeze to the earliest first freeze, that's a 203-day window you can count on — up to 221 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
Illinois runs as cold as USDA zone 5, and no sourced winter-hardiness floor is on record for mountain laurel, so this page does not state whether it overwinters here — and gives no fall establishment date on the strength of a guess. Whether mountain laurel is a permanent planting or a replant-every-spring crop for you turns on your own zone within Illinois; check its hardiness range against that before treating it as long-lived ground.
Timing tuned to sub-state frost dates — Jo Daviess 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 mountain laurel survives winter here. Whether the season is long enough — and warm enough — is a different question.
Frost-free days
Mountain Laurel wants 150+ frost-free days; a typical Illinois site sees ~212 (NOAA Regional Climate Centers ACIS, 1991-2020). That leaves comfortable headroom for succession planting.
Chill hours
Mountain Laurel requires ~600 chill hours (32-45°F dormancy window). Illinois 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
Mountain Laurel prefers acidic soil (pH 4.5-5.5). Illinois's prairie loam can run on the acidic side, which often aligns well — confirm with a soil test before planting.
Your land, not the state average
Illinois soil pH runs about 6.2–6.7, and that sits above mountain laurel's tolerated 4.5–5.5, so the typical Illinois parcel needs sulfur to bring it down. SSURGO maps it swinging by full points parcel to parcel, so your map unit, not the state number, decides whether mountain laurel needs lime or sulfur.
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. Illinois soil profile from USDA NRCS SSURGO. Site-specific verification: a 30-minute soil test from your local Extension lab.
What Else to Consider for Mountain Laurel in Illinois
Zone compatibility tells you about winter cold survival — but Illinois growers also need to think about:
Heavy clay soils in northern IL drain poorly
Extreme temperature swings between summer and winter
Japanese beetles are a major garden pest
Growing mountain laurel here specifically
Mountain Laurel does best acidic (pH 4.5–5.5); Illinois soils average near pH 6.5, alkaline enough to yellow its leaves as micronutrients lock away.
Work in elemental sulfur or acidic organic matter to pull your parcel toward pH 4.5–5.5, then retest. How to handle it →
What to actually do about these — and the constraints that apply to every Illinois grower, not just mountain laurel — is covered on the Illinois growing guide.
Timing shifts within Illinois
Illinois isn't one climate. In Jo Daviess County, the last hard freeze (28°F) holds until about Apr 22 — roughly 20 days later than the recorded state median — so plant mountain laurel to your county's window, not the statewide date.
Mountain Laurel needs about 150 days of frost-free season to complete its cycle. Even Jo Daviess County — Illinois’s shortest season at 177 frost-free days — clears that by 27 days, so season length isn’t the constraint anywhere in Illinois. What varies is your own parcel.
Across Illinois’s 102 counties the frost-free season runs from 177 days in Jo Daviess County to 244 days in Alexander County — a spread of 67 days, which is why a single statewide planting date misleads. The median Illinois county sees 212 frost-free days, leaving mountain laurel about 62 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"). Mountain Laurel'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
Mountain Laurel draws native bees (moderate value, Growable Ground Plant Database). Planting it near vegetable beds can lift fruit set on neighboring crops. Outdoors, mountain laurel can only work that bloom inside Illinois's frost window — roughly 212 days, opening after the last 28°F freeze (Mar 29 - Apr 8) and closing at the first (Oct 28 - Nov 5), per NOAA Regional Climate Centers ACIS, 1991-2020.
Good to Know Before You Plant Mountain Laurel
Mountain Laurel is listed as toxic to dogs, cats, horses (all) at a severe level (ASPCA). Most listed plants only cause brief upset — a raised bed or a fenced corner usually keeps curious pets clear.
Illinois Cooperative Extension
For Illinois-specific cultivar recommendations, planting calendars, and pest pressure for mountain laurel, the canonical source is University of Illinois Extension. Their fact sheets carry the local trial data we can't generalize across 50 states.
Is Mountain Laurel native to Illinois?
Mountain Laurel is native to parts of the Lower 48, but the USDA PLANTS Database (accessed 2026-07-01) does not document a native range in Illinois. It can still earn a place in a Illinois garden — the zone comparison above tells you whether it will thrive.
Looking for plants that belong here? The Illinois 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 Mountain Laurel in Illinois
When can I plant Mountain Laurel in Illinois?
Illinois's last spring hard freeze (28°F) clears between Mar 29 and Apr 8, and the first fall hard freeze lands between Oct 28 and Nov 5 (NOAA Regional Climate Centers ACIS, 1991-2020). No sourced winter-hardiness floor is on record for Mountain Laurel, so this page does not state whether it overwinters in Illinois 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 Mountain Laurel grown in across Illinois?
Illinois spans USDA hardiness zones 5a-7b (USDA ARS PHZM 2023). Mountain Laurel 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 Illinois site have?
A typical Illinois site sees ~212 frost-free days per year (derived from NOAA Regional Climate Centers ACIS, 1991-2020). Mountain Laurel 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 Jo Daviess, the freeze-free season runs shorter than the state average, so verify your own county's window.
Is Mountain Laurel native to Illinois?
Mountain Laurel is native to parts of the Lower 48, but the USDA PLANTS Database (accessed 2026-07-01) does not document a native range in Illinois. It can still earn a place in a Illinois garden — the zone comparison above tells you whether it will thrive.
How should I amend the soil for Mountain Laurel in Illinois?
Mountain Laurel prefers pH 4.5-5.5 (USDA PLANTS). Most Illinois soils run mildly acidic to neutral; many sites land near this band naturally, and a soil test plus targeted sulfur or organic amendment closes any gap.
Will Mountain Laurel actually grow on my specific land in Illinois?
State-level zone + climate data is a sketch. A Growable Ground parcel report scores mountain laurel 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 Illinois
State-level data is a sketch. Your Growable Ground report scores mountain laurel against your parcel's exact soil, sun, drainage, and frost data — not zone averages.
Three things about your lot that Illinois mountain laurel averages can't show:
We read public map data around Illinois — soil, climate, flood, and parcel records. How we handle your address.
25+ data sources read at your address, not the Illinois mountain laurel average
Explore More
Growing guides for mountain laurel
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
Last updated: