Altha, Florida, sits in USDA hardiness zone 9a — a zone band wide enough that plant choice, not possibility, is the interesting question.
A short list that earns its place here — artichoke, fig, california poppy, and cabbage — with any one site's soil, sun, and drainage making the final cut.
Even in Altha, no two yards are alike.
A low spot, a south-facing slope, or a stand of trees moves the frost date and sun across a single Altha lot. 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 Altha — soil, climate, flood, and parcel records. How we handle your address.
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Altha — the short answer
Altha, Florida: USDA zone 9a, about 295 days between hard freezes, across 856 acres of town.
- USDA zone
- 9a
- USDA PHZM 2023
- Last hard freeze (28°F)
- Feb 10
- Calhoun County normal — NOAA 1991–2020, nearest to this town
- First hard freeze (28°F)
- Dec 2
- Calhoun County normal — NOAA 1991–2020, nearest to this town
- Days between freezes
- ~295
- Calhoun County normal — NOAA 1991–2020, nearest to this town
- Town area
- 856 acres
- US Census TIGER/Line 2025
Every figure names the dataset it came from. No 30-year normal resolves at this town’s own centroid, so the hard-freeze dates are Calhoun County’s — the closest measured record, labelled as such rather than passed off as local.
Hardiness Zone Range
Zone 9a is Altha's average, not your lot's — a low corner or a tree line moves it. Against Altha's 295-day season, see what your own ground reads.
Soil varies lot by lot — soil types explained.
What this means for growing in Altha
Each reading below is measured for Altha itself — here is what it means for a garden here, and the move an experienced grower makes about it.
Season length
From county recordsAltha runs about 295 days between hard freezes (read from Calhoun County, the closest normal to Altha) — 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
MeasuredAltha 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 Altha is in
Altha sits in the Southeastern Plains — EPA Level III, inside the wider Eastern Temperate Forests. That is read at Altha's own centroid rather than borrowed from Calhoun County.
What Grows in Altha
Every plant below cleared Altha's own zone 9a and its 295-day season. Each card opens that plant's Florida profile. How we score.
Is it too late to plant in Altha?
Too late for some crops, right on time for others — a growing season is a sequence, not a deadline. Cool-season crops can go in from around Jan 13; tender transplants wait until two to three weeks after the last 28°F hard freeze, which lands near Feb 10 (NOAA 1991–2020 climate normals); and from midsummer, planting counts back from the first fall freeze around Dec 2 — long-season crops need about 90 days of runway, quick greens only 30. With almost year-round growing weather, timing is about heat and rainfall more than frost — some bench is always in play.
What's on the federal record near Altha
Closest first, within ~10 miles of Altha. Listing isn't leaking, and distance isn't exposure.
- CALHOUN CNTY SCHOOL BD-ALTHA SCHOOLUnderground Storage Tanks · 250 ft
- SOUTHERN EXPRESS #12Underground Storage Tanks · 800 ft
- ALTHA LAUDROMATUnderground Storage Tanks · 900 ft
- BAILEY PURE OIL (FORMER)Underground Storage Tanks · 1000 ft
- CITY GARAGE & SUPPLY COBrownfields · 1100 ft
- CITY GARAGE & SUPPLY COUnderground Storage Tanks · 1100 ft
- SOUTHERN EXPRESS #6Underground Storage Tanks · 1300 ft
- THOMAS PROPERTYUnderground Storage Tanks · 0.7 mi
- POLAN HALLUnderground Storage Tanks · 0.8 mi
- ALTHA FARMERS CO-OP INCUnderground Storage Tanks · 1.3 mi
- MELTON BROS FARMUnderground Storage Tanks · 1.3 mi
- BAGGETT BROTHERS FARM INCUnderground Storage Tanks · 1.7 mi
6 more sites are on the record inside the same radius. See them on the map
Measured from Altha'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 Altha.
Sources Checked
within ~10 miles of Altha
Severity Distribution
within ~10 miles of Altha
Highest-Severity Sites
A note from Gnorman
What an experienced grower watches for around here
In and around Altha, Underground Storage Tanks runs higher than the national average — 60 sites within ~10 miles of Altha. It's not cause for alarm — it's worth knowing, and there's a sensible way to grow around it.
Underground Storage Tanks: Underground storage tanks are the single most common source of soil contamination near homes and gardens.
Use raised beds with imported soil — this eliminates the primary soil-contact pathway.
Check your specific parcel in Altha
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 Altha average
Your land is one point inside Altha
Everything above resolves to Altha as a whole — one PHZM band, read across 856 acres, with hard-freeze dates borrowed from Calhoun County’s record because no 30-year normal resolves at this town’s own centroid. 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 town 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 local average.
Your Lot vs the Altha Average
Altha Average
- ●USDA Zones 9a, averaged across Altha
- ●One soil character for all of Altha
- ●Frost dates read at Altha's scale: Feb 10 to Dec 2
YOUR Parcel
- ✓Your exact zone, not Altha's 9a
- ✓Your SSURGO soil type & pH
- ✓Your sun exposure, cast in 3D
See MY Growing Report
Read your specific parcel in Altha
Pull a site-specific report for your exact address in Altha, Florida — soil, sun, drainage, frost risk, and scored plant recommendations.
Three things about your lot that Altha averages can't show:
We read public map data around Altha — soil, climate, flood, and parcel records. How we handle your address.
25+ data sources read at your address, not the Altha average
How we know this about Altha
The datasets: hardiness from the USDA ARS Plant Hardiness Zone Map 2023, read at this town’s own centroid; hard-freeze dates from NOAA 1991–2020 28°F normals at Calhoun County’s record, because none resolves here; boundaries and acreage from US Census TIGER/Line 2025; the contamination records from the federal sources named in their beats above. Soil is not read at town grain anywhere on this page — there is no town-resolution survey in our data, which is why you will find no soil grid here rather than a statewide one wearing a local label. The resolution ledger below names every figure this page inherited.
Common questions about Altha
When does frost risk typically end in Altha?
The last hard freeze (28°F) in Altha typically lands around Feb 10, 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 3.
When is the first frost in Altha?
The first hard freeze (28°F) in Altha typically arrives around Dec 2, per NOAA 1991–2020 climate normals — the point tender summer crops finish. Lighter frosts run ahead of it, near Nov 18, so the watching starts about Nov 2 — about 295 days after the spring freeze cleared.
How long is the growing season in Altha?
Measured between 28°F hard freezes, Altha sees about 295 frost-free days — roughly Feb 10 through Dec 2, per NOAA 1991–2020 climate normals. Tender crops work a shorter one: nearer Mar 3 to Nov 18, about 260 days.
Is the soil safe to grow vegetables in Altha?
The federal record around Altha is a meaningful one — 83 documented sites, mostly Underground Storage Tanks entries (60), the nearest Underground Storage Tanks record under a tenth of a mile out — so a soil test before new food beds is a sensible precaution here, not a reason to hold back from growing. Remember that proximity to a documented site is information, not a diagnosis of any one yard; the contamination map shows exactly what sits where.
How do I protect my plants from frost in Altha?
From about Nov 2 the job here turns from planting to protecting — the last start even a 30-day crop can finish. As the season closes around the first 28°F hard freeze near Dec 2 (NOAA 1991–2020 climate normals), three moves buy time: row cover or an old sheet over tender plants on still, clear nights; water the soil the afternoon before a freeze, so it holds warmth overnight; and harvest tomatoes, peppers and basil before Dec 2. Hardy greens and roots shrug off light frost and sweeten after it — leave them in.
Everything above is measured at Altha's scale — its 9a band and its 295-day season. Your yard writes its own version of Altha's numbers: we read soil, sun, drainage and frost at your exact address. Try it for 14 days — no card required.
What this page reads at Altha’s own scale
5 of the readings below were taken at Altha's own scale — the 856 acres it covers and 83 documented sites around it; 5 are borrowed from a wider read, named and linked below.
Measured here
- Altha's own USDA hardiness band, zones 9aUSDA PHZM 2023
- 83 documented contamination sites on the federal record near Altha, the closest Underground Storage Tanks record under a tenth of a mile out from the town centreFederal environmental registers
- Altha's boundary and the 856 acres inside itUS Census TIGER/Line 2025
- Which of 1,086 plants clear zones 9a and a ~295-day seasonGrowable Ground crop-matching engine
- The ecoregion at Altha's own centroid, the Southeastern PlainsUS EPA Level III Ecoregions
Inherited from a wider read
- The 28°F hard-freeze dates — Altha has no normal of its own, so its county's is the closest measured readfrom Calhoun County
- Soil character — no town-scale survey exists, so Altha's 856 acres read through its county's SSURGO summaryfrom Calhoun County
- Growing-degree days and winter chill — measured county-wide only, so the county page carries themfrom Calhoun County
- The growing challenges every Florida grower plans around — written at state scale, so they stay on the state guidefrom Florida
- Butterfly and beetle records, and the farmland pesticide estimate — all published county-widefrom Calhoun County
What this page can’t tell you
- The soil pH, drainage, sun hours, and frost pockets on any one lot among Altha's 856 acreswhy one lot differs from the next →
- Which side of Altha you're on — a low spot frosts first and a south wall warms early, and one normal is being asked to speak for all 856 acresreading your own microclimate →
- How close that record sits to YOUR lot — the closest Underground Storage Tanks record under a tenth of a mile out, measured from the town centrehow we read the record →
- Where cold air settles, which slopes face the sun, and which way the wind runs on your own ground — measured at your address, and averaged away by any Altha-wide figureread your own land →
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