Yes — Strong Match
ammi 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 ~60 ammi needs.
Sow by about Sep 6
Ammi 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 Louisiana season runs ~298 frost-free days, leaving 238 days of slack. That is room to sow as late as about Sep 6 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 →
60 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.
Your yard isn't the whole zone.
Ammi 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 ammi 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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Zone Comparison
Ammi Needs
- USDA Zones: Data pending
- Frost-Free Days: 60+
- Sun: Full Sun
- Mature size: 3.5 ft tall
- Picking window: ~60 days of harvest
- Drought tolerance: Low
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: USDA PLANTS Database / Growable Ground plant catalog. State data: USDA ARS PHZM 2023, NOAA Climate Normals, NRCS SSURGO.
When to Plant Ammi 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.
When to start the seed
Ammi is direct-sown where it grows rather than started under cover, so there is no seed-tray head start to bank — Louisiana's dates above are the whole calendar for it. That makes the last-freeze date the binding constraint, and a warmer pocket of your own yard is worth more to this crop than it is to a transplanted one.
Days to maturity vs. the window
At 90 days to maturity (USDA PLANTS Database), counting from the last hard freeze it ripens with 196 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: 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
Ammi wants 60+ 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
Ammi needs ~1000 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
Ammi 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
Louisiana's soils run mostly silt loam, but SSURGO maps the series, texture, and drainage under your exact parcel. What matters for ammi is the horizon its roots actually work, not the surface. That map unit, not the state average, decides how ammi performs.
Check your parcel → Source: USDA NRCS SSURGO.
Plant pH and drainage requirements from USDA PLANTS Database. Louisiana soil profile from USDA NRCS SSURGO. Site-specific verification: a 30-minute soil test from your local Extension lab.
Ammi in Louisiana — Quick Answer
- Verdict: Yes — Strong Match
- Plant Zones: Data pending (USDA PLANTS Database)
- State Zones: 8b-10b (USDA ARS PHZM 2023)
- Growing Season: 28°F hard freezes about Jan 30 - Feb 17 to Nov 30 - Dec 8 (NOAA Regional Climate Centers ACIS, 1991-2020)
- Days to Maturity: 90 days
What Else to Consider for Ammi 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 ammi here specifically
Louisiana's soils run mostly silt loam (Alfisols), and whether that suits ammi's pH 6.0–7.0 preference comes down to your exact parcel, not the statewide picture.
Pull your parcel's SSURGO map unit, test pH, and amend toward ammi's 6.0–7.0 target before planting. How to handle it →
What to actually do about these — and the constraints that apply to every Louisiana grower, not just ammi — 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 ammi to your county's window, not the statewide date.
Ammi needs about 60 days of frost-free season to complete its cycle. Even Claiborne County — Louisiana’s shortest season at 265 frost-free days — clears that by 205 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 ammi about 238 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"). Ammi'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
Ammi 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, ammi 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.
Good to Know Before You Plant Ammi
Ammi is listed as toxic to dogs, cats (all) at a mild level (Cornell). Most listed plants only cause brief upset — a raised bed or a fenced corner usually keeps curious pets clear. Worth knowing for placement: in Louisiana this is a one-season plant and the first hard freeze (Nov 30 - Dec 8) takes it down, so the exposure above is a summer-long one rather than something standing in the bed all year.
Recommended Ammi Varieties for Louisiana
Louisiana publishes no state variety trial for ammi, 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 ammi, the canonical source is LSU AgCenter. Their fact sheets carry the local trial data we can't generalize across 50 states.
Is Ammi native to Louisiana?
No — the USDA PLANTS Database lists Ammi 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 Ammi in Louisiana
When can I plant Ammi 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). 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 Ammi mature before first frost in Louisiana?
Yes — Ammi matures in 90 days (USDA PLANTS Database), and Louisiana's dependable hard-freeze-free window runs 286 days (NOAA Regional Climate Centers ACIS, 1991-2020), leaving 196 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 Ammi grown in across Louisiana?
Louisiana spans USDA hardiness zones 8b-10b (USDA ARS PHZM 2023). Ammi 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). Ammi 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 Claiborne, the freeze-free season runs shorter than the state average, so verify your own county's window.
Is Ammi native to Louisiana?
No — the USDA PLANTS Database lists Ammi 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 Ammi in Louisiana?
Ammi 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 Ammi actually grow on my specific land in Louisiana?
State-level zone + climate data is a sketch. A Growable Ground parcel report scores ammi 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 ammi against your parcel's exact soil, sun, drainage, and frost data — not zone averages.
Three things about your lot that Louisiana ammi 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 ammi average
Explore More
Growing guides for ammi
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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