Yes — Strong Match
cosmos is grown as an annual, so season length decides it here, not a winter zone — and Louisiana's typical season runs ~298 frost-free days against the ~50 cosmos needs.
Sow by about Sep 26
Cosmos is grown as an annual, so what decides it here is season length, not a winter zone. It needs about 50 frost-free days and a typical Louisiana season runs ~298 frost-free days, leaving 248 days of slack. That is room to sow as late as about Sep 26 and still finish before the usual first freeze (Dec 5), or to run a second succession.
Want more weeks at either end of that window? How to buy the weeks →
50 frost-free days required against Louisiana’s ~298-day season. NOAA Regional Climate Centers ACIS 1991-2020 (28°F killing freeze), state median across counties, via stateClimateData.ts.
Cosmos in Louisiana — the short answer
Cosmos in Louisiana: full sun, against a state median of ~298 frost-free days.
- Louisiana zones
- 8b-10b
- USDA PHZM 2023
- Frost window
- Jan 30 - Feb 17 – Nov 30 - Dec 8
- NOAA RCC ACIS 1991-2020, 28°F
- Shortest county season
- 265 days
- NOAA Regional Climate Centers ACIS, 1991-2020, county 28°F killing freeze
- Days to maturity
- 70 days
- Growable Ground Plant Database
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.
Cosmos is grown as an annual, so your winter zone isn't the deciding factor — your frost-free window is. A typical Louisiana site runs ~298 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 cosmos against your land's actual frost dates, sun, and soil.
We read public map data for this spot — soil, climate, flood, and parcel records. How we handle your address.
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Louisiana is not one climate
A single Louisiana answer averages 64 counties whose growing seasons are 100 days apart — from 265 frost-free days in Claiborne County to 365 in Plaquemines County. Which end of that your land sits nearer changes what cosmos can finish before the first hard freeze.
The middle half of 64 counties runs 285–313 days, with a median of 298 days — a 100-day span end to end.
Measured across 64 Louisiana 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.
Zone Comparison
Cosmos Needs
- USDA Zones: Data pending
- Frost-Free Days: 50+
- Sun: Full Sun
- Mature size: 4 ft tall
- Picking window: ~120 days of harvest
- Drought tolerance: Medium
Louisiana Has
- USDA Zones: 8b-10b
- Last Hard Freeze (28°F): Jan 30 - Feb 17
- First Hard Freeze (28°F): Nov 30 - Dec 8
- Annual Rainfall: 50-65 inches
- Common Soils: Alluvial clay, Muck, Sandy loam
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 Cosmos in Louisiana
The frost window
Across Louisiana, the last spring hard freeze (28°F) clears between Jan 30 and Feb 17, and the first fall hard freeze lands between Nov 30 and Dec 8 (NOAA Regional Climate Centers ACIS, 1991-2020). Counting from the latest last freeze to the earliest first freeze, that's a 286-day window you can count on — up to 312 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.
Frost tenderness
Cosmos is frost-tender — FAO ECOCROP puts its killing temperature at 32°F — so set plants out two to three weeks PAST your local last hard freeze, not on it and not on the state's earliest date. The 28°F marker above is when killing freezes stop, not when light frost does. That is the point where cold damages growing tissue, not a winter-survival floor — an established perennial comes through far colder while dormant, which is what its hardiness zone tells you.
When to start the seed
Those dates are when cosmos goes out, not when it starts. It is sown under cover about 4 weeks ahead, so counting back from Louisiana's late-side last freeze of Feb 17 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 70 days to maturity (Growable Ground Plant Database), counting from the last hard freeze it ripens with 216 days to spare even in Louisiana's tightest freeze scenario — room for a later start or a second sowing.
Timing tuned to sub-state frost dates — Claiborne 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
Frost-free days
Cosmos wants 50+ frost-free days; a typical Louisiana site sees ~298 (NOAA Regional Climate Centers ACIS, 1991-2020). That leaves comfortable headroom for succession planting.
Growing degree days
Cosmos needs ~900 GDD (base 50°F) to ripen. The state median runs ~6204 GDD (from PRISM 1991-2020 climate normals), so Louisiana'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
Cosmos likes near-neutral soil (pH 6-7). That's the common-ground band across Louisiana's alluvial clay and muck — a soil test confirms it for your site. Drainage matters: this plant wants well (dry spells). If your Louisiana 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 45.5% of Louisiana as poorly or somewhat-poorly drained, and the class flips parcel to parcel. Cosmos sits mid-range for drought tolerance, so either extreme can 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. Louisiana soil profile from USDA NRCS SSURGO. Site-specific verification: a 30-minute soil test from your local Extension lab.
What Else to Consider for Cosmos in Louisiana
Zone compatibility tells you about winter cold survival — but Louisiana growers also need to think about:
Extreme humidity and rainfall promote rot and fungal diseases
Poor drainage in delta and coastal areas
Hurricane damage risk from June through November
Growing cosmos here specifically
Cosmos likes pH 6.0–7.0 and its growing tissue burns around 32°F (FAO ECOCROP), yet neither saves it from wet feet — SSURGO maps about 45.5% of Louisiana poorly-drained, where its roots sit and rot.
Set cosmos high on bermed, grit-amended ground so winter and storm water drain away from the roots. How to handle it →
What to actually do about these — and the constraints that apply to every Louisiana grower, not just cosmos — is covered on the Louisiana growing guide.
Timing shifts within Louisiana
Louisiana isn't one climate. In Claiborne County, the last hard freeze (28°F) holds until about Mar 2 — roughly 19 days later than the recorded state median — so plant cosmos to your county's window, not the statewide date.
Cosmos needs about 50 days of frost-free season to complete its cycle. Even Claiborne County — Louisiana’s shortest season at 265 frost-free days — clears that by 215 days, so season length isn’t the constraint anywhere in Louisiana. What varies is your own parcel.
Across Louisiana’s 64 counties the frost-free season runs from 265 days in Claiborne County to 365 days in Plaquemines County — a spread of 100 days, which is why a single statewide planting date misleads. The median Louisiana county sees 298 frost-free days, leaving cosmos about 248 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"). Cosmos's 50-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
Cosmos draws honeybees, native bees, and butterflies (high value, Growable Ground Plant Database). Planting it near vegetable beds can lift fruit set on neighboring crops. Outdoors, cosmos can only work that bloom inside Louisiana's frost window — roughly 298 days, opening after the last 28°F freeze (Jan 30 - Feb 17) and closing at the first (Nov 30 - Dec 8), per NOAA Regional Climate Centers ACIS, 1991-2020.
Recommended Cosmos Varieties for Louisiana
Louisiana publishes no state variety trial for cosmos, so we won't invent a "best for Louisiana" list. Choose types rated to your USDA hardiness zone (8b-10b), and confirm winter survival and drainage against your own parcel.
Louisiana Cooperative Extension
For Louisiana-specific cultivar recommendations, planting calendars, and pest pressure for cosmos, the canonical source is LSU AgCenter. Their fact sheets carry the local trial data we can't generalize across 50 states.
Is Cosmos native to Louisiana?
No — the USDA PLANTS Database lists Cosmos as introduced rather than native in the Lower 48, so it is not part of Louisiana's native flora. It grows here as a garden plant; pairing it with a few Louisiana natives keeps local pollinators fed too.
Looking for plants that belong here? The Louisiana 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 Cosmos in Louisiana
When can I plant Cosmos in Louisiana?
Louisiana's last spring hard freeze (28°F) clears between Jan 30 and Feb 17, and the first fall hard freeze lands between Nov 30 and Dec 8 (NOAA Regional Climate Centers ACIS, 1991-2020). Cosmos is frost-tender — its killing temperature is 32°F (FAO ECOCROP — the point where cold damages growing tissue, not a winter-survival floor) — so wait two to three weeks past your site's last hard freeze, when light frost has also stopped, before planting out.
Can Cosmos mature before first frost in Louisiana?
Yes — Cosmos matures in 70 days (Growable Ground Plant Database), and Louisiana's dependable hard-freeze-free window runs 286 days (NOAA Regional Climate Centers ACIS, 1991-2020), leaving 216 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 Cosmos grown in across Louisiana?
Louisiana spans USDA hardiness zones 8b-10b (USDA ARS PHZM 2023). Cosmos 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 Louisiana site have?
A typical Louisiana site sees ~298 frost-free days per year (derived from NOAA Regional Climate Centers ACIS, 1991-2020). Cosmos needs 50+ 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 Claiborne, the freeze-free season runs shorter than the state average, so verify your own county's window.
Is Cosmos native to Louisiana?
No — the USDA PLANTS Database lists Cosmos as introduced rather than native in the Lower 48, so it is not part of Louisiana's native flora. It grows here as a garden plant; pairing it with a few Louisiana natives keeps local pollinators fed too.
How should I amend the soil for Cosmos in Louisiana?
Cosmos prefers pH 6-7 and well (dry spells) drainage (Growable Ground Plant Database). That sits in the common-ground band across Louisiana soils — a 30-minute soil test from a local Extension lab confirms it for your specific site.
Will Cosmos actually grow on my specific land in Louisiana?
State-level zone + climate data is a sketch. A Growable Ground parcel report scores cosmos 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 Louisiana
State-level data is a sketch. Your Growable Ground report scores cosmos against your parcel's exact soil, sun, drainage, and frost data — not zone averages.
Three things about your lot that Louisiana cosmos averages can't show:
We read public map data around Louisiana — soil, climate, flood, and parcel records. How we handle your address.
25+ data sources read at your address, not the Louisiana cosmos average
Explore More
Growing guides for cosmos
Explore Louisiana county by county
Louisiana carries 64 counties with their own USDA zone — a sample of the growing pages for cosmos there:
Where else cosmos grows
Cosmos's zone band crosses state lines — these are the states closest to Louisiana 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 Louisiana
Louisiana has a growing page for 1,030 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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