Yes — Strong Match
zinnia is grown as an annual, so season length decides it here, not a winter zone — and Kentucky's typical season runs ~221 frost-free days against the ~60 zinnia needs.
Sow by about Sep 3
Zinnia is grown as an annual, so what decides it here is season length, not a winter zone. It needs about 60 frost-free days and a typical Kentucky season runs ~221 frost-free days, leaving 161 days of slack. That is room to sow as late as about Sep 3 and still finish before the usual first freeze (Nov 7), or to run a second succession.
Want more weeks at either end of that window? How to buy the weeks →
60 frost-free days required against Kentucky’s ~221-day season. NOAA Regional Climate Centers ACIS 1991-2020 (28°F killing freeze), state median across counties, via stateClimateData.ts.
Your yard isn't the whole zone.
Zinnia is grown as an annual, so your winter zone isn't the deciding factor — your frost-free window is. A typical Kentucky site runs ~221 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 zinnia against your land's actual frost dates, sun, and soil.
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Zone Comparison
Zinnia Needs
- USDA Zones: Data pending
- Frost-Free Days: 60+
- Sun: Full Sun
- Mature size: 3 ft tall
- Picking window: ~120 days of harvest
- Drought tolerance: Medium
Kentucky Has
- USDA Zones: 6a-7b
- Last Hard Freeze (28°F): Mar 27 - Apr 2
- First Hard Freeze (28°F): Nov 4 - Nov 10
- Annual Rainfall: 42-52 inches
- Common Soils: Silt loam, Clay loam, Limestone-derived
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 Zinnia in Kentucky
The frost window
Across Kentucky, the last spring hard freeze (28°F) clears between Mar 27 and Apr 2, and the first fall hard freeze lands between Nov 4 and Nov 10 (NOAA Regional Climate Centers ACIS, 1991-2020). Counting from the latest last freeze to the earliest first freeze, that's a 216-day window you can count on — up to 228 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 zinnia goes out, not when it starts. It is sown under cover about 4 weeks ahead, so counting back from Kentucky's late-side last freeze of Apr 2 is what fixes your sowing date — and a yard that clears frost earlier than the state's late date starts earlier still.
Days to maturity vs. the window
At 65 days to maturity (USDA PLANTS Database), counting from the last hard freeze it ripens with 151 days to spare even in Kentucky's tightest freeze scenario — room for a later start or a second sowing.
Timing tuned to sub-state frost dates — Greenup 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
Frost-free days
Zinnia wants 60+ frost-free days; a typical Kentucky site sees ~221 (NOAA Regional Climate Centers ACIS, 1991-2020). That leaves comfortable headroom for succession planting.
Growing degree days
Zinnia needs ~800 GDD (base 50°F) to ripen. The state median runs ~3689 GDD (from PRISM 1991-2020 climate normals), so Kentucky'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
Zinnia likes near-neutral soil (pH 5.5-7.5). That's the common-ground band across Kentucky's silt loam and clay 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 Kentucky soil test result is a problem or just a number. Drainage matters: this plant wants well (dry spells). If your Kentucky site is heavier clay or sits in a low spot, raised beds or amendment with compost solve it.
Your land, not the state average
Kentucky's soils run mostly silt loam, but SSURGO maps the series, texture, and drainage under your exact parcel. What matters for zinnia is the horizon its roots actually work, not the surface. That map unit, not the state average, decides how zinnia performs.
Check your parcel → Source: USDA NRCS SSURGO.
Plant pH and drainage requirements from USDA PLANTS Database. Kentucky soil profile from USDA NRCS SSURGO. Site-specific verification: a 30-minute soil test from your local Extension lab.
Zinnia in Kentucky — Quick Answer
- Verdict: Yes — Strong Match
- Plant Zones: Data pending (USDA PLANTS Database)
- State Zones: 6a-7b (USDA ARS PHZM 2023)
- Growing Season: 28°F hard freezes about Mar 27 - Apr 2 to Nov 4 - Nov 10 (NOAA Regional Climate Centers ACIS, 1991-2020)
- Days to Maturity: 65 days
What Else to Consider for Zinnia in Kentucky
Zone compatibility tells you about winter cold survival — but Kentucky growers also need to think about:
Heavy clay soils in the Bluegrass region
High humidity promotes fungal diseases
Karst topography creates drainage unpredictability
Growing zinnia here specifically
Kentucky's soils run mostly silt loam (Alfisols), and whether that suits zinnia's pH 5.5–7.5 preference comes down to your exact parcel, not the statewide picture.
Pull your parcel's SSURGO map unit, test pH, and amend toward zinnia's 5.5–7.5 target before planting. How to handle it →
What to actually do about these — and the constraints that apply to every Kentucky grower, not just zinnia — is covered on the Kentucky growing guide.
Timing shifts within Kentucky
Kentucky isn't one climate. In Greenup County, the last hard freeze (28°F) holds until about Apr 13 — roughly 13 days later than the recorded state median — so plant zinnia to your county's window, not the statewide date.
Zinnia needs about 60 days of frost-free season to complete its cycle. Even Greenup County — Kentucky’s shortest season at 195 frost-free days — clears that by 135 days, so season length isn’t the constraint anywhere in Kentucky. What varies is your own parcel.
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"). Zinnia's 60-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
Zinnia draws honeybees, native bees, butterflies, and hummingbirds (high value, Growable Ground Plant Database). Planting it near vegetable beds can lift fruit set on neighboring crops. Outdoors, zinnia can only work that bloom inside Kentucky's frost window — roughly 221 days, opening after the last 28°F freeze (Mar 27 - Apr 2) and closing at the first (Nov 4 - Nov 10), per NOAA Regional Climate Centers ACIS, 1991-2020.
Recommended Zinnia Varieties for Kentucky
Kentucky publishes no state variety trial for zinnia, so we won't invent a "best for Kentucky" list. Choose types rated to your USDA hardiness zone (6a-7b), and confirm winter survival and drainage against your own parcel.
Kentucky Cooperative Extension
For Kentucky-specific cultivar recommendations, planting calendars, and pest pressure for zinnia, the canonical source is University of Kentucky Cooperative Extension. Their fact sheets carry the local trial data we can't generalize across 50 states.
Is Zinnia native to Kentucky?
No — the USDA PLANTS Database lists Zinnia as introduced rather than native in the Lower 48, so it is not part of Kentucky's native flora. It grows here as a garden plant; pairing it with a few Kentucky natives keeps local pollinators fed too.
Looking for plants that belong here? The Kentucky 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 Zinnia in Kentucky
When can I plant Zinnia in Kentucky?
Kentucky's last spring hard freeze (28°F) clears between Mar 27 and Apr 2, and the first fall hard freeze lands between Nov 4 and Nov 10 (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.
Can Zinnia mature before first frost in Kentucky?
Yes — Zinnia matures in 65 days (USDA PLANTS Database), and Kentucky's dependable hard-freeze-free window runs 216 days (NOAA Regional Climate Centers ACIS, 1991-2020), leaving 151 days of margin. Plant once the last hard freeze has passed — two to three weeks later for anything tender — and it ripens ahead of the first fall freeze.
What hardiness zone is Zinnia grown in across Kentucky?
Kentucky spans USDA hardiness zones 6a-7b (USDA ARS PHZM 2023). Zinnia carries a range of zones Data pending, so the overlap zones are where outdoor growing is most reliable.
How many frost-free days does a typical Kentucky site have?
A typical Kentucky site sees ~221 frost-free days per year (derived from NOAA Regional Climate Centers ACIS, 1991-2020). Zinnia needs 60+ 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 Greenup, the freeze-free season runs shorter than the state average, so verify your own county's window.
Is Zinnia native to Kentucky?
No — the USDA PLANTS Database lists Zinnia as introduced rather than native in the Lower 48, so it is not part of Kentucky's native flora. It grows here as a garden plant; pairing it with a few Kentucky natives keeps local pollinators fed too.
How should I amend the soil for Zinnia in Kentucky?
Zinnia prefers pH 5.5-7.5 and well (dry spells) drainage (Growable Ground Plant Database). That sits in the common-ground band across Kentucky soils — a 30-minute soil test from a local Extension lab confirms it for your specific site.
Will Zinnia actually grow on my specific land in Kentucky?
State-level zone + climate data is a sketch. A Growable Ground parcel report scores zinnia 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 Kentucky
State-level data is a sketch. Your Growable Ground report scores zinnia against your parcel's exact soil, sun, drainage, and frost data — not zone averages.
Three things about your lot that Kentucky zinnia averages can't show:
We read public map data around Kentucky — soil, climate, flood, and parcel records. How we handle your address.
25+ data sources read at your address, not the Kentucky zinnia average
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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