Unlikely — Zone Mismatch
caladium (zones 9-11) does not overlap with Illinois's zone range (5a-7b). Growing outdoors is unlikely without significant protection.
2 zones short — what would close it
Caladium is hardy to zone 9, and the warmest ground in Illinois is zone 7 — 2 zones short. Planted in open ground it will not survive a Illinois winter. To grow it here, grow caladium in an earth-sheltered greenhouse — its modeled 2.5-zone lift covers this gap.
An earth-sheltered greenhouse is the lift this needs. How a greenhouse changes what you can grow →
Zone math from 9-11 (plant) against 5-7 (Illinois). Lift modeled by crop_engine.GREENHOUSE_ZONE_MODIFIER_BY_SUBTYPE['earth_sheltered'] (+2.5 zones) via api/fast_sections.py Unlock Engine v2.
Caladium in Illinois — the short answer
Caladium in Illinois: hardy in zones 9–11, full sun, against a state median of ~212 frost-free days.
- Plant zones
- 9-11
- 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 has its own microclimate — slope, trees, and low spots shift frost and sun across a single parcel. Enter your address and we'll score caladium against your land's actual soil, sun, and frost.
We read public map data for this spot — soil, climate, flood, and parcel records. How we handle your address.
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Illinois is not one climate
A single Illinois answer averages 102 counties whose growing seasons are 67 days apart — from 177 frost-free days in Jo Daviess County to 244 in Alexander County. Which end of that your land sits nearer changes what caladium can finish before the first hard freeze.
The middle half of 102 counties runs 203–221 days, with a median of 212 days — a 67-day span end to end.
Measured across 102 Illinois counties. NOAA Regional Climate Centers ACIS, 1991-2020, county 28°F killing freeze. 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 Caladium Stands in Illinois
Caladium is rated for zones 9–11 — a cold floor USDA puts at 20 to 30°F. No Illinois 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 Illinois winters, not about caladium.
Below the zone 9 floor
102 counties
- Carroll County · zone 5a
- Jo Daviess County · zone 5a
- Stephenson County · zone 5a
3 of 102 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
Caladium Needs
- USDA Zones: 9-11
- Frost-Free Days: 180+
- Sun: Full Sun
- Mature size: 2 ft tall
- Picking window: ~90 days of harvest
- Drought tolerance: Low
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 9-11)
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 Caladium 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.
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 caladium does not survive a Illinois 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 Illinois under protection.
Frost-free days
Caladium wants 180+ frost-free days; a typical Illinois site sees ~212 (NOAA Regional Climate Centers ACIS, 1991-2020). That leaves a workable window — start indoors to bank time.
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
Caladium tolerates a wide pH range (pH 4.3-8.2) — 3.9 units, acid ground through alkaline — so soil acidity is rarely what limits it in Illinois. A soil test is still worth having, but for what else it tells you about this site, not to clear this plant. 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 Illinois soil test result is a problem or just a number. Drainage matters: this plant wants poorly (saturated >50% of year), well (dry spells). If your Illinois site is heavier clay or sits in a low spot, raised beds or amendment with compost solve it.
Your land, not the state average
SSURGO maps about 52.0% of Illinois as poorly or somewhat-poorly drained, and the class flips parcel to parcel. Caladium has low drought tolerance, so it is the fast-draining end that will cost you — your soil map unit, not the state average, is the real answer.
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 Caladium 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 caladium here specifically
Caladium roots run medium and prefer pH 4.3–8.2, but drainage comes first here: SSURGO maps about 52.0% of Illinois as poorly or somewhat-poorly drained, and wet ground rots its roots before pH ever matters.
Plant caladium on a raised, gravel-amended berm so water drains fast and the roots stays dry. How to handle it →
What to actually do about these — and the constraints that apply to every Illinois grower, not just caladium — 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 caladium to your county's window, not the statewide date.
Caladium needs about 180 days of frost-free season to complete its cycle. 100 of Illinois’s 102 counties give it that outright. The tightest that does is Stephenson County at 188 frost-free days — 8 to spare. Below that line you are transplanting or extending the season, not direct-sowing.
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 caladium about 32 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"). Caladium's 180-day requirement: USDA PLANTS / Growable Ground plant database (minimum frost-free days). A parcel report resolves your address's own frost dates.
Good to Know Before You Plant Caladium
Caladium 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. Worth knowing for placement: in Illinois this is a one-season plant and the first hard freeze (Oct 28 - Nov 5) takes it down, so the exposure above is a summer-long one rather than something standing in the bed all year.
Recommended Caladium Varieties for Illinois
Illinois publishes no state variety trial for caladium, so we won't invent a "best for Illinois" list. Choose types rated to your USDA hardiness zone (5a-7b), and confirm winter survival and drainage against your own parcel.
Illinois Cooperative Extension
For Illinois-specific cultivar recommendations, planting calendars, and pest pressure for caladium, the canonical source is University of Illinois Extension. Their fact sheets carry the local trial data we can't generalize across 50 states.
Common Questions About Growing Caladium in Illinois
When can I plant Caladium 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). Time outdoor planting to after the last hard freeze for your specific site — a further two to three weeks for anything tender — and count back from those dates for transplant scheduling.
What hardiness zone is Caladium grown in across Illinois?
Illinois spans USDA hardiness zones 5a-7b (USDA ARS PHZM 2023). Caladium 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 Illinois site have?
A typical Illinois site sees ~212 frost-free days per year (derived from NOAA Regional Climate Centers ACIS, 1991-2020). Caladium needs 180+ 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.
How should I amend the soil for Caladium in Illinois?
Caladium tolerates pH 4.3-8.2 and poorly (saturated >50% of year), well (dry spells) drainage (FAO ECOCROP). That is a 3.9-unit span, acid ground through alkaline, so pH is rarely what limits this plant on a Illinois site — amend for drainage and organic matter first.
Will Caladium actually grow on my specific land in Illinois?
State-level zone + climate data is a sketch. A Growable Ground parcel report scores caladium 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 caladium against your parcel's exact soil, sun, drainage, and frost data — not zone averages.
Three things about your lot that Illinois caladium 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 caladium average
Explore More
Growing guides for caladium
Explore Illinois county by county
Illinois carries 102 counties with their own USDA zone — a sample of the growing pages for caladium there:
Where else caladium grows
Caladium's zone band crosses state lines — these are the states closest to Illinois 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 Illinois
Illinois has a growing page for 893 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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