Yes — Strong Match
plains coreopsis is grown in zones 2-11, which covers every zone Illinois contains (5a-7b). Whether the season is long enough is the question that remains.
Plains Coreopsis in Illinois — the short answer
Plains Coreopsis in Illinois: grown in zones 2–11, full sun, against a state median of ~212 frost-free days.
- Plant zones
- Grown as an annual — see the growing season
- Growing season, not a hardiness zone
- 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.
Plains Coreopsis is grown as an annual, so your winter zone isn't the deciding factor — your frost-free window is. A typical Illinois site runs ~212 frost-free days, but that is a state median, not your yard: slope, trees, and low spots move the last-frost date across a single parcel. Enter your address and we'll score plains coreopsis against your land's actual frost dates, sun, and soil.
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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 plains coreopsis 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 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 plains coreopsis (USDA PHZM 2023):
Zone Comparison
Plains Coreopsis Needs
- USDA Zones: 2-11
- Sun: Full Sun
- Mature size: 3 ft tall
- Picking window: ~60 days of harvestWe haven't confirmed this against a published source yet.
- 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 2-11)
Preferred Soil pH
We haven't confirmed this against a published source yet.
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 Plains Coreopsis 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.
When to start the seed
Those dates are when plains coreopsis goes out, not when it starts. It is sown under cover about 6 weeks ahead, so counting back from Illinois's late-side last freeze of Apr 8 is what fixes your sowing date — and a yard that clears frost earlier than the state's late date starts earlier still.
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.
Soil + Drainage Fit
Plains Coreopsis likes near-neutral soil (pH 5.5-7.5). That's the common-ground band across Illinois's prairie loam and silt loam — a soil test confirms it for your site. It will grow across that whole span, but it does best between pH 6 and 7 — worth knowing before you decide whether a Illinois soil test result is a problem or just a number. Drainage matters: this plant wants well (dry spells). If your Illinois site is heavier clay or sits in a low spot, a raised bed lifts the roots above wet ground, or work in compost. pH range and preferred pH: We haven't confirmed this against a published source yet.
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 Plains Coreopsis in Illinois
The zone range tells you where plains coreopsis is grown — 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
What to actually do about these — and the constraints that apply to every Illinois grower, not just plains coreopsis — is covered on the Illinois growing guide.
Where in Illinois Plains Coreopsis Is Zone-Hardy
Plains Coreopsis is rated for USDA zones 2–11. Every one of Illinois’s 102 counties sits inside that band — from Carroll County at zone 5a to Williamson County at zone 7a — so winter cold is not what decides this plant anywhere in the state. What is left to vary is your own parcel: slope, shelter and cold-air drainage routinely move a site half a zone either way from the county figure.
Across those 102 counties Illinois’s winter-low ladder runs from zone 5a in Carroll County to zone 7a in Williamson County — 2 USDA zones of spread, which is 20°F between the two counties’ average coldest night of the year. That is why a statewide hardiness answer is where you start and not where you finish.
The planting window moves with it. Jo Daviess County holds its last hard freeze (28°F) until about Apr 22, while Alexander County is clear by Mar 17 — 36 days apart. Set plains coreopsis out on your county’s date, not the state’s.
County hardiness zones: USDA Plant Hardiness Zone Map (PHZM) 2023, per county. County last-freeze dates: NOAA Regional Climate Centers ACIS (1991-2020), county 28°F killing freeze — earlier than the folk 32°F "last frost". Plains Coreopsis’s zone 2–11 band: a season crop, no zone claim. A parcel report resolves your address’s own zone and frost dates rather than its county’s.
Pollinator + Wildlife Value
Plains Coreopsis draws honeybees, native bees, and butterflies (high value). Planting it near vegetable beds can lift fruit set on neighboring crops. Outdoors, plains coreopsis 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. Pollinator value: We haven't confirmed this against a published source yet.
Illinois Cooperative Extension
For Illinois-specific cultivar recommendations, planting calendars, and pest pressure for plains coreopsis, the canonical source is University of Illinois Extension. Their fact sheets carry the local trial data we can't generalize across 50 states.
Is Plains Coreopsis native to Illinois?
The USDA PLANTS Database (accessed 2026-10-19) lists Plains Coreopsis as native to the Lower 48 and records it growing in Illinois, but it does not say whether those Illinois plants are native or introduced. Your state's native plant society or Cooperative Extension can tell you whether it is part of the local flora.
State records: USDA PLANTS Database state-distribution data (presence, not state-level nativity), accessed 2026-10-19.
Common Questions About Growing Plains Coreopsis in Illinois
When can I plant Plains Coreopsis 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 Plains Coreopsis grown in across Illinois?
Illinois spans USDA hardiness zones 5a-7b (USDA ARS PHZM 2023). Plains Coreopsis carries a range of zones 2-11, 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). Plains Coreopsis 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.
Is Plains Coreopsis native to Illinois?
The USDA PLANTS Database (accessed 2026-10-19) lists Plains Coreopsis as native to the Lower 48 and records it growing in Illinois, but it does not say whether those Illinois plants are native or introduced. Your state's native plant society or Cooperative Extension can tell you whether it is part of the local flora.
How should I amend the soil for Plains Coreopsis in Illinois?
Plains Coreopsis prefers pH 5.5-7.5 and well (dry spells) drainage. We haven't confirmed this against a published source yet. That sits in the common-ground band across Illinois soils — a 30-minute soil test from a local Extension lab confirms it for your specific site.
Will Plains Coreopsis actually grow on my specific land in Illinois?
State-level zone + climate data is a sketch. A Growable Ground parcel report scores plains coreopsis against your address's mapped 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 plains coreopsis against your land's mapped soil, modelled sun, drainage, and frost data — not zone averages.
Three things about your lot that Illinois plains coreopsis 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 plains coreopsis average
Explore More
Growing guides for plains coreopsis
Explore Illinois county by county
Illinois carries 102 counties with their own USDA zone — a sample of the growing pages for plains coreopsis there:
Where else plains coreopsis grows
Plains Coreopsis'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 889 plants — a rotating sample of the rest of the shelf.
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