St. Tammany Parish, in Louisiana, sits in USDA hardiness zone 9a — a range where zone-matched perennials and frost-aware annual timing set what succeeds.
Among the crops suited to this profile: artichoke, fig, california poppy, and cabbage. The site-level story — soil, sun, drainage — decides the rest.
St. Tammany Parish lies within the Gulf Coast — a regional growing area with its own character.
Grounded in USDA PHZM 2023 · Growable Ground suitability scoring · NOAA 1991–2020 Climate Normals
St. Tammany Parish holds more than one microclimate.
Soils and elevations shift across St. Tammany Parish, so your frost dates and drainage aren't the county average. Enter your address and we'll score 1,086 plants against your land's actual soil, sun, and frost.
We read public map data around St. Tammany Parish — soil, climate, flood, and parcel records. How we handle your address.
No card required · your full report in seconds
St. Tammany Parish — the short answer
St. Tammany Parish, Louisiana: USDA zone 9a, about 300 days between hard freezes, across 541K acres.
- USDA zone
- 9a
- USDA PHZM 2023
- Last hard freeze (28°F)
- Feb 8
- NOAA 1991–2020 Climate Normals, 28°F
- First hard freeze (28°F)
- Dec 5
- NOAA 1991–2020 Climate Normals, 28°F
- Days between freezes
- ~300
- NOAA 1991–2020 Climate Normals, 28°F
- County area
- 541K acres
- US Census TIGER/Line 2025
Every figure names the dataset it came from. Hard-freeze dates are county 28°F normals: light frosts run a few weeks past them, and tender transplants usually wait 2–3 weeks after the last hard freeze.
Hardiness Zone Range
Zone 9a is St. Tammany Parish's average, not your lot's — a low corner or a tree line moves it. Against St. Tammany Parish's 300-day season, see what your own ground reads.
Heat and winter chill in St. Tammany Parish
Across a year, St. Tammany Parish accumulates about 6,626 growing degree days above 50°F, about 330 more than the middle Louisiana county — ahead of 41 of Louisiana’s 64 counties. Degree days are the heat a crop actually gets to work with — more of them is more room to ripen a long-season crop before the freeze closes the window.
Winter banks about 406 hours below 45°F, 206 fewer than the Louisiana middle of 612. Chill is what tells a fruit tree its dormancy is over, and it is set by climate rather than by anything you can build.
Grounded in PRISM Climate Group, Oregon State University — 1991–2020 monthly normals
Soil in St. Tammany County
Across St. Tammany County, the ground is predominantly Ultisols, where Myatt, Stough, and Savannah are the most extensive named soil series. The soil is generally somewhat poorly drained with a fine sandy loam surface. Topsoil pH runs about 5.0–5.3, strongly acidic. Rainfall drains through hydrologic group C/D soils.
Soil order
Ultisols
Drainage
Somewhat poorly drained
Prime farmland
38%
Hydric soils
54%
Soil still varies lot by lot — soil types explained.
How the ground varies across St. Tammany Parish
The USDA soil survey maps 22% of St. Tammany Parish as somewhat poorly drained — but another 53% drains differently: 19% poorly drained, 16% moderately well drained.
Myatt is the most extensive named soil at 18% of mapped acres, then Stough (16%) and Savannah (14%).
Which of them your own lot sits on is a parcel question, not a county one. Check your address for the survey at your boundary.
What this means for growing in St. Tammany Parish
Each reading below is measured for St. Tammany Parish itself — here is what it means for a garden here, and the move an experienced grower makes about it.
Drainage
MeasuredThe dominant soils across St. Tammany Parish are somewhat poorly drained, in hydrologic group C/D — ground that sheds water slowly.
Beds can stay saturated for days after heavy rain, and the roots of most vegetables, berries, and fruit trees suffocate or rot in soil that never drains.
Raised beds or mounded rows lift roots above the wet zone; choose water-tolerant crops for the lowest spots.
USDA NRCS SSURGO
Surface pH
MeasuredTopsoil across St. Tammany Parish runs about pH 5.0–5.3, on the acidic side.
Blueberries, potatoes, and rhododendrons thrive in it, but most vegetables start locking out nutrients below about pH 6.0 and grow pale and stunted no matter how much you feed them.
A measured lime application raises pH for the crops that need it — but test first, because the right rate depends on your own soil, not the county average.
USDA NRCS SSURGO
Season length
MeasuredSt. Tammany Parish runs about 300 days between hard freezes — close to year-round growing.
Frost is rarely the limit here; winter plantings are as real as summer ones, and the harder question is which crops shrug off the summer heat.
Grow cool-season crops through the mild winter, and choose heat-tolerant varieties for the summer beds.
NOAA 1991–2020 Climate Normals
Winter hardiness
MeasuredSt. Tammany Parish sits in USDA hardiness zone 9a.
The zone sets which perennials, shrubs, and fruit trees live through an average winter here — a plant rated for a colder zone is a safe bet, one rated warmer needs winter protection or gets treated as an annual.
Match perennials and fruit to the zone before you buy, so nothing you plant is a gamble against the cold.
USDA PHZM 2023
The kind of country St. Tammany Parish is in
St. Tammany Parish spans 3 EPA Level III ecoregions — Southern Coastal Plain (55%), Mississippi Alluvial Plain (25%) and Southeastern Plains (20%). Which one your land falls in changes what grows wild there and how the ground behaves, and a county-wide answer cannot tell you which.
What Grows in St. Tammany Parish
We scored all 1,086 plants against St. Tammany Parish's own USDA zone 9a and its own 300-day season between hard freezes, using the same matching engine that runs a full parcel report. These cleared both. Sun, soil pH and drainage vary lot by lot — those are the parcel questions below. Each card opens that plant's Louisiana profile.
Is it too late to plant in St. Tammany Parish?
For most of the year, no — what changes is which crops still fit the days remaining. Cool-season crops can go in from around Jan 11; tender transplants wait until two to three weeks after the last 28°F hard freeze, which lands near Feb 8 (NOAA 1991–2020 climate normals); and from midsummer, planting counts back from the first fall freeze around Dec 5 — long-season crops need about 90 days of runway, quick greens only 30. And with a calendar this mild, the honest answer is that planting barely stops — winter opens seasons colder regions never see.
Documented around St. Tammany Parish
- monarch butterfly140 documented records
Sighting records, so they follow observers as much as insects.
What gets applied to farmland in St. Tammany Parish
USGS estimates 5,429 lb of 2,4-d on St. Tammany Parish farmland in 2019, its largest by weight, ahead of Glyphosate (1,820 lb) and Triclopyr (1,112 lb).
Farmland across the whole county, not any one lot. Check your address for the site-by-site record.
Safe to Grow Here?
What the federal record shows across St. Tammany County — and how to grow with it.
We checked the federal record across St. Tammany County — 1,420 documented sites across 6 of the 9 source types we track.
The most significant on record: 7 Superfund sites. Sites tracked in EPA's Superfund program — from assessment-stage CERCLIS entries to confirmed National Priorities List cleanup sites.
St. Tammany Parish carries one of the heavier federal records we track — and that's not a verdict on your yard. Proximity to a documented site is information, not a diagnosis: nothing here says any particular parcel is affected. It does earn one concrete step — before food beds go in the ground, a professional soil test tells you exactly what you're working with, and raised beds with clean imported soil grow well almost anywhere in the meantime.
Sources: EPA, USGS — 1.8M documented sites tracked nationwide across 9 federal source types.
What's on the federal record near St. Tammany Parish
Closest first, across St. Tammany County. Listing isn't leaking, and distance isn't exposure.
- ST-606Nitrate · 2.8 mi
- SOUTHERN NATURAL GAS CO - LACOMBE COMPRESSOR STATIONBrownfields · 3.0 mi
- ST-692Nitrate · 3.4 mi
- Greater St Tammany AirportUnderground Storage Tanks · 3.7 mi
- ST TAMMANY PARISH CORONER'S COMPLEXBrownfields · 3.7 mi
- Cross Country ChevronUnderground Storage Tanks · 3.9 mi
- PAVESTONE - NEW ORLEANS, LA PLANTToxics Release Inventory · 4.1 mi
- OCHSNER CLINIC FOUNDATIONBrownfields · 4.1 mi
- BEACON BEHAVIORAL HOSPITALBrownfields · 4.1 mi
- US EPA-- HURRICANE KATRINABrownfields · 4.2 mi
- Lacombe Travel Center IncUnderground Storage Tanks · 4.2 mi
- LACOMBE TRAVEL CENTER INCBrownfields · 4.2 mi
6 more sites are on the record inside the same radius. See them on the map
Measured from St. Tammany Parish's center, not your beds. Run your own address for what's upwind of you specifically.
Environmental Intelligence
The counts behind that headline — every source type on the record near St. Tammany Parish.
Sources Checked
across St. Tammany County
Severity Distribution
across St. Tammany County
Highest-Severity Sites
A note from Gnorman
What an experienced grower watches for around here
In and around St. Tammany Parish, two things run higher than the national average across St. Tammany County — PFAS (18 sites) and Brownfields (759 sites). That's not a problem with your land — it's information about it.
PFAS: PFAS (per- and polyfluoroalkyl substances) are called "forever chemicals" because they do not biodegrade.
Brownfields: Brownfield sites are former commercial or industrial properties where legacy soil contamination (heavy metals, PAHs, petroleum compounds) may persist.
Test irrigation water source — this is the primary pathway for PFAS to reach garden crops.
Check EPA brownfield remediation status — many sites have completed cleanup with institutional controls.
Check your specific parcel in St. Tammany Parish
Get exact proximity distances to contamination sources for your specific parcel — plus soil, sun, drainage, and 1,086 plant recommendations.
25+ data sources read at your address, not the St. Tammany Parish average
Your land is one point inside St. Tammany Parish
Everything above resolves to St. Tammany Parish as a whole — one PHZM band and one county frost record, read across 541K acres. Your parcel is one point inside that footprint. Slope, tree cover, a low spot that pools cold air, and what is in the soil are all resolved at the address, and none of them are visible at county scale. That is the honest boundary of this page, and the reason the next step is a reading of your own ground rather than a better county average.
Your Lot vs the St. Tammany Parish Average
St. Tammany Parish Average
- ●USDA Zones 9a, averaged across St. Tammany Parish
- ●One soil character for all of St. Tammany Parish
- ●Frost dates read at St. Tammany Parish's scale: Feb 8 to Dec 5
YOUR Parcel
- ✓Your exact zone, not St. Tammany Parish's 9a
- ✓Your SSURGO soil type & pH
- ✓Your sun exposure, cast in 3D
See MY Growing Report
Read your parcel in St. Tammany Parish
Pull a site-specific report for your exact address in St. Tammany Parish, Louisiana — soil, sun, drainage, frost risk, and scored plant recommendations.
Three things about your lot that St. Tammany Parish averages can't show:
We read public map data around St. Tammany Parish — soil, climate, flood, and parcel records. How we handle your address.
25+ data sources read at your address, not the St. Tammany Parish average
How we know this about St. Tammany Parish
The datasets: hardiness from the USDA ARS Plant Hardiness Zone Map 2023, read at county grain; hard-freeze dates from NOAA 1991–2020 28°F normals at this county’s own record where one resolves, and the labelled statewide window where none does; soils from the USDA NRCS SSURGO survey, area-weighted across the county’s own map units; boundaries and acreage from US Census TIGER/Line 2025; the contamination and pesticide records from the federal sources named in their beats above. Where St. Tammany Parish carries no record of its own, the figure is inherited and labelled — the resolution ledger below names each.
Common questions about St. Tammany Parish
When does frost risk typically end in St. Tammany Parish?
The last hard freeze (28°F) in St. Tammany Parish typically lands around Feb 8, per NOAA 1991–2020 climate normals — earlier than the light-frost dates most charts quote. That marks the hard freeze, not the last light frost — lighter frosts keep biting past it, which is why tender transplants here wait until about Mar 1.
How long is the growing season in St. Tammany Parish?
Measured between 28°F hard freezes, St. Tammany Parish sees about 300 frost-free days — roughly Feb 8 through Dec 5, per NOAA 1991–2020 climate normals. Tender crops work a shorter one: nearer Mar 1 to Nov 21, about 265 days.
Is the soil safe to grow vegetables in St. Tammany Parish?
The federal record around St. Tammany Parish runs heavier than most — 1,420 documented sites, mostly Brownfields entries (759), the nearest Nitrate record about 2.8 miles out — so test the soil before planting food in the ground, and raised beds with clean imported soil grow well in the meantime. Even here, proximity to a documented site is information, not a diagnosis of any one yard; the contamination map shows exactly what's recorded and where.
Everything above is measured at St. Tammany Parish's scale — its 9a band and its 300-day season. Your yard writes its own version of St. Tammany Parish's numbers: we read soil, sun, drainage and frost at your exact address. Try it for 14 days — no card required.
Will It Grow Here?
Zone fit is the first question — each answer below reads Louisiana's frost window, season length, and soil profile against the plant's real requirements.
What this page reads at St. Tammany Parish’s own scale
9 of the readings below were taken at St. Tammany Parish's own scale — its own ~300-day span between 28°F freezes, the 3 most extensive soil series mapped here and 1,420 documented sites inside its boundary; one is borrowed from a wider read, named and linked below.
Measured here
- St. Tammany Parish's own USDA hardiness band, zones 9aUSDA PHZM 2023
- St. Tammany Parish's own 28°F hard-freeze dates and its ~300-day span between themNOAA 1991–2020 Climate Normals
- The soil order, drainage, surface pH, and the 3 most extensive named soil series mapped in St. Tammany ParishUSDA NRCS SSURGO
- 1,420 documented contamination sites inside the county boundary, distance-sorted from its center — the closest Nitrate record about 2.8 miles outFederal environmental registers
- St. Tammany Parish's boundary and the 540,996 acres inside itUS Census TIGER/Line 2025
- Which of 1,086 plants clear zones 9a and a ~300-day seasonGrowable Ground crop-matching engine
- The 3 ecoregions St. Tammany Parish spans, Southern Coastal Plain the largestUS EPA Level III Ecoregions
- Open occurrence records documented in St. Tammany Parish for a tracked speciesGBIF derived datasets (CC0 / CC BY 4.0)
- Which agricultural compounds go onto St. Tammany Parish farmland, and roughly how muchUSGS NAWQA EPest county estimates
Inherited from a wider read
- The growing challenges every Louisiana grower plans around — written at state scale, so they stay on the state guidefrom Louisiana
What this page can’t tell you
- How the season shifts across St. Tammany Parish — the ~300 days above is one reading at its centre; the 12 towns below each carry their owntowns in this county →
- The soil pH, drainage, sun hours, and frost pockets on any one lot among St. Tammany Parish's 540,996 acreswhy one lot differs from the next →
- Which of those 1,420 documented sites actually reaches your soil — that needs your address, the wind, and the groundwater directionhow we read the record →
- Where cold air settles, which slopes face the sun, and which way the wind runs on your own ground — none of it survives being averaged over St. Tammany Parishread your own land →