Yes — Strong Match
Mexican sunflower is grown as an annual, so season length decides it here, not a winter zone — and Indiana's typical season runs ~209 frost-free days against the ~70 Mexican sunflower needs.
Sow by about Aug 14
Mexican Sunflower is grown as an annual, so what decides it here is season length, not a winter zone. It needs about 70 frost-free days and a typical Indiana season runs ~209 frost-free days, leaving 139 days of slack. That is room to sow as late as about Aug 14 and still finish before the usual first freeze (Nov 2).
Want more weeks at either end of that window? How to buy the weeks →
70 frost-free days required against Indiana’s ~209-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.
Mexican Sunflower is grown as an annual, so your winter zone isn't the deciding factor — your frost-free window is. A typical Indiana site runs ~209 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 mexican sunflower against your land's actual frost dates, sun, and soil.
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Zone Comparison
Mexican Sunflower Needs
- USDA Zones: Data pending
- Frost-Free Days: 70+
- Sun: Full Sun
- Mature size: 5 ft tall
- Picking window: ~90 days of harvest
- Drought tolerance: High
Indiana Has
- USDA Zones: 5b-7b
- Last Hard Freeze (28°F): Apr 4 - Apr 9
- First Hard Freeze (28°F): Oct 30 - Nov 4
- Annual Rainfall: 36-46 inches
- Common Soils: Silt loam, Clay loam, Glacial till
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 Mexican Sunflower in Indiana
The frost window
Across Indiana, the last spring hard freeze (28°F) clears between Apr 4 and Apr 9, and the first fall hard freeze lands between Oct 30 and Nov 4 (NOAA Regional Climate Centers ACIS, 1991-2020). Counting from the latest last freeze to the earliest first freeze, that's a 204-day window you can count on — up to 214 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 mexican sunflower goes out, not when it starts. It is sown under cover about 6 weeks ahead, so counting back from Indiana's late-side last freeze of Apr 9 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 80 days to maturity (USDA PLANTS Database), counting from the last hard freeze it ripens with 124 days to spare even in Indiana's tightest freeze scenario — room for a later start or a second sowing.
Timing tuned to sub-state frost dates — Steuben 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
Mexican Sunflower wants 70+ frost-free days; a typical Indiana site sees ~209 (NOAA Regional Climate Centers ACIS, 1991-2020). That leaves comfortable headroom for succession planting.
Growing degree days
Mexican Sunflower needs ~1800 GDD (base 50°F) to ripen. The state median runs ~3153 GDD (from PRISM 1991-2020 climate normals), so Indiana'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
Mexican Sunflower likes near-neutral soil (pH 5.5-7.5). That's the common-ground band across Indiana'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 Indiana soil test result is a problem or just a number. Drainage matters: this plant wants well (dry spells). If your Indiana site is heavier clay or sits in a low spot, raised beds or amendment with compost solve it.
Your land, not the state average
Indiana's soils run mostly silt loam, but SSURGO maps the series, texture, and drainage under your exact parcel. What matters for mexican sunflower is the horizon its roots actually work, not the surface. That map unit, not the state average, decides how mexican sunflower performs.
Check your parcel → Source: USDA NRCS SSURGO.
Plant pH and drainage requirements from USDA PLANTS Database. Indiana soil profile from USDA NRCS SSURGO. Site-specific verification: a 30-minute soil test from your local Extension lab.
Mexican Sunflower in Indiana — Quick Answer
- Verdict: Yes — Strong Match
- Plant Zones: Data pending (USDA PLANTS Database)
- State Zones: 5b-7b (USDA ARS PHZM 2023)
- Growing Season: 28°F hard freezes about Apr 4 - Apr 9 to Oct 30 - Nov 4 (NOAA Regional Climate Centers ACIS, 1991-2020)
- Days to Maturity: 80 days
What Else to Consider for Mexican Sunflower in Indiana
Zone compatibility tells you about winter cold survival — but Indiana growers also need to think about:
Heavy clay soils limit drainage in many areas
Late spring frosts through early May
Hot humid summers promote blight and mildew
Growing mexican sunflower here specifically
Mexican Sunflower needs pH 5.5–7.5; Indiana's dominant silt loam soils may or may not deliver that, so your parcel's SSURGO map unit is the real test.
Start with a soil test on your own ground and adjust pH and texture to fit mexican sunflower's 5.5–7.5 range. How to handle it →
What to actually do about these — and the constraints that apply to every Indiana grower, not just mexican sunflower — is covered on the Indiana growing guide.
Timing shifts within Indiana
Indiana isn't one climate. In Steuben County, the last hard freeze (28°F) holds until about Apr 18 — roughly 11 days later than the recorded state median — so plant mexican sunflower to your county's window, not the statewide date.
Mexican Sunflower needs about 70 days of frost-free season to complete its cycle. Even Steuben County — Indiana’s shortest season at 191 frost-free days — clears that by 121 days, so season length isn’t the constraint anywhere in Indiana. 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"). Mexican Sunflower's 70-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
Mexican Sunflower 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, mexican sunflower can only work that bloom inside Indiana's frost window — roughly 209 days, opening after the last 28°F freeze (Apr 4 - Apr 9) and closing at the first (Oct 30 - Nov 4), per NOAA Regional Climate Centers ACIS, 1991-2020.
Recommended Mexican Sunflower Varieties for Indiana
Indiana publishes no state variety trial for mexican sunflower, so we won't invent a "best for Indiana" list. Choose types rated to your USDA hardiness zone (5b-7b), and confirm winter survival and drainage against your own parcel.
Indiana Cooperative Extension
For Indiana-specific cultivar recommendations, planting calendars, and pest pressure for mexican sunflower, the canonical source is Purdue Extension. Their fact sheets carry the local trial data we can't generalize across 50 states.
Is Mexican Sunflower native to Indiana?
No — the USDA PLANTS Database lists Mexican Sunflower as introduced rather than native in the Lower 48, so it is not part of Indiana's native flora. It grows here as a garden plant; pairing it with a few Indiana natives keeps local pollinators fed too.
Looking for plants that belong here? The Indiana 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 Mexican Sunflower in Indiana
When can I plant Mexican Sunflower in Indiana?
Indiana's last spring hard freeze (28°F) clears between Apr 4 and Apr 9, and the first fall hard freeze lands between Oct 30 and Nov 4 (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 Mexican Sunflower mature before first frost in Indiana?
Yes — Mexican Sunflower matures in 80 days (USDA PLANTS Database), and Indiana's dependable hard-freeze-free window runs 204 days (NOAA Regional Climate Centers ACIS, 1991-2020), leaving 124 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 Mexican Sunflower grown in across Indiana?
Indiana spans USDA hardiness zones 5b-7b (USDA ARS PHZM 2023). Mexican Sunflower 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 Indiana site have?
A typical Indiana site sees ~209 frost-free days per year (derived from NOAA Regional Climate Centers ACIS, 1991-2020). Mexican Sunflower needs 70+ 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 Steuben, the freeze-free season runs shorter than the state average, so verify your own county's window.
Is Mexican Sunflower native to Indiana?
No — the USDA PLANTS Database lists Mexican Sunflower as introduced rather than native in the Lower 48, so it is not part of Indiana's native flora. It grows here as a garden plant; pairing it with a few Indiana natives keeps local pollinators fed too.
How should I amend the soil for Mexican Sunflower in Indiana?
Mexican Sunflower prefers pH 5.5-7.5 and well (dry spells) drainage (Growable Ground Plant Database). That sits in the common-ground band across Indiana soils — a 30-minute soil test from a local Extension lab confirms it for your specific site.
Will Mexican Sunflower actually grow on my specific land in Indiana?
State-level zone + climate data is a sketch. A Growable Ground parcel report scores mexican sunflower 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 Indiana
State-level data is a sketch. Your Growable Ground report scores mexican sunflower against your parcel's exact soil, sun, drainage, and frost data — not zone averages.
Three things about your lot that Indiana mexican sunflower averages can't show:
We read public map data around Indiana — soil, climate, flood, and parcel records. How we handle your address.
25+ data sources read at your address, not the Indiana mexican sunflower average
Explore More
Growing guides for mexican sunflower
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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