San Marcos, Texas, sits in USDA hardiness zone 9a — a band that supports both cool-season staples and warm-season crops chosen to fit the local frost window.
These conditions suit artichoke, fig, california poppy, and cabbage — a starting list any specific site will trim or extend with its own soil, sun, and drainage.
Even in San Marcos, 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 San Marcos 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 San Marcos — soil, climate, flood, and parcel records. How we handle your address.
No card required · your full report in seconds
San Marcos — the short answer
San Marcos, Texas: USDA zone 9a, about 289 days between hard freezes, across 26K acres of city.
- USDA zone
- 9a
- USDA PHZM 2023
- Last hard freeze (28°F)
- Feb 16
- Hays County normal — NOAA 1991–2020, nearest to this town
- First hard freeze (28°F)
- Dec 2
- Hays County normal — NOAA 1991–2020, nearest to this town
- Days between freezes
- ~289
- Hays County normal — NOAA 1991–2020, nearest to this town
- City area
- 26K 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 Hays County’s — the closest measured record, labelled as such rather than passed off as local.
Hardiness Zone Range
Zone 9a is San Marcos's average, not your lot's — a low corner or a tree line moves it. Against San Marcos's 289-day season, see what your own ground reads.
Soil varies lot by lot — soil types explained.
What this means for growing in San Marcos
Each reading below is measured for San Marcos itself — here is what it means for a garden here, and the move an experienced grower makes about it.
Season length
From county recordsSan Marcos runs about 289 days between hard freezes (read from Hays County, the closest normal to San Marcos) — 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
MeasuredSan Marcos 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 San Marcos is in
San Marcos sits in the Texas Blackland Prairies — EPA Level III, inside the wider Great Plains. That is read at San Marcos's own centroid, and it is not what its county reads: Hays County is mostly Edwards Plateau. The wider page above you is answering a different question about different ground.
What Grows in San Marcos
Every plant below cleared San Marcos's own zone 9a and its 289-day season. Each card opens that plant's Texas profile. How we score.
Is it too late to plant in San Marcos?
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 19; tender transplants wait until two to three weeks after the last 28°F hard freeze, which lands near Feb 16 (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. And with a calendar this mild, the honest answer is that planting barely stops — winter opens seasons colder regions never see.
Documented around San Marcos
Survey cells within 31 miles of San Marcos checked for spotted lanternfly, none carrying a detection — a surveyed negative, not an absence of looking. Nearest documented record 630 miles off. What to watch for.
What's on the federal record near San Marcos
Closest first, within ~10 miles of San Marcos. Listing isn't leaking, and distance isn't exposure.
- UNITED PARCEL SERVICEUnderground Storage Tanks · 700 ft
- SAN MARCOS TRUCK STOP 9Underground Storage Tanks · 850 ft
- EXXON MUFFLER & RADIATOR SHOPUnderground Storage Tanks · 1000 ft
- STRIPES 1517Underground Storage Tanks · 1200 ft
- SAN MARCOS VACUUMUnderground Storage Tanks · 1400 ft
- CHEVRON 123Underground Storage Tanks · 1600 ft
- COMMERCIAL OFFICE SUPPLYUnderground Storage Tanks · 1700 ft
- CHUCK NASH CHEVROLETUnderground Storage Tanks · 2300 ft
- PHILLIPS 66Underground Storage Tanks · 2400 ft
- FAST BREAK 10Underground Storage Tanks · 2500 ft
- DOUGLAS C BROWNUnderground Storage Tanks · 2600 ft
- SERVICE KING PAINT & BODY, LLCBrownfields · 0.5 mi
6 more sites are on the record inside the same radius. See them on the map
Measured from San Marcos'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 San Marcos.
Total Sites
345
within ~10 miles of San Marcos
Risk Level
Elevated
Highest-severity
12 Toxics Release Inventory facilities
Sources Checked
within ~10 miles of San Marcos
Severity Distribution
within ~10 miles of San Marcos
Highest-Severity Sites
A note from Gnorman
What an experienced grower watches for around here
In and around San Marcos, two things run higher than the national average within ~10 miles of San Marcos — Nitrate (162 sites) and PFAS (4 sites). That's not a problem with your land — it's information about it.
Nitrate: Nitrate contamination primarily comes from agricultural fertilizer runoff and failing septic systems.
PFAS: PFAS (per- and polyfluoroalkyl substances) are called "forever chemicals" because they do not biodegrade.
Test well water for nitrate if you rely on a private well for irrigation (EPA standard: 10 mg/L).
Test irrigation water source — this is the primary pathway for PFAS to reach garden crops.
Check your specific parcel in San Marcos
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 San Marcos average
Your land is one point inside San Marcos
Everything above resolves to San Marcos as a whole — one PHZM band, read across 26K acres, with hard-freeze dates borrowed from Hays County’s record because no 30-year normal resolves at this city’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 city 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 San Marcos Average
San Marcos Average
- ●USDA Zones 9a, averaged across San Marcos
- ●One soil character for all of San Marcos
- ●Frost dates read at San Marcos's scale: Feb 16 to Dec 2
YOUR Parcel
- ✓Your exact zone, not San Marcos's 9a
- ✓Your SSURGO soil type & pH
- ✓Your sun exposure, cast in 3D
See MY Growing Report
Read your specific parcel in San Marcos
Pull a site-specific report for your exact address in San Marcos, Texas — soil, sun, drainage, frost risk, and scored plant recommendations.
Three things about your lot that San Marcos averages can't show:
We read public map data around San Marcos — soil, climate, flood, and parcel records. How we handle your address.
25+ data sources read at your address, not the San Marcos average
How we know this about San Marcos
The datasets: hardiness from the USDA ARS Plant Hardiness Zone Map 2023, read at this city’s own centroid; hard-freeze dates from NOAA 1991–2020 28°F normals at Hays 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 city grain anywhere on this page — there is no city-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 San Marcos
When does frost risk typically end in San Marcos?
The last hard freeze (28°F) in San Marcos typically lands around Feb 16, 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 9.
When is the first frost in San Marcos?
The first hard freeze (28°F) in San Marcos 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 289 days after the spring freeze cleared.
How long is the growing season in San Marcos?
Measured between 28°F hard freezes, San Marcos sees about 289 frost-free days — roughly Feb 16 through Dec 2, per NOAA 1991–2020 climate normals. Tender crops work a shorter one: nearer Mar 9 to Nov 18, about 254 days.
Is the soil safe to grow vegetables in San Marcos?
The federal record around San Marcos is a meaningful one — 345 documented sites, mostly Nitrate entries (162), the nearest Underground Storage Tanks record about 0.1 miles 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 San Marcos?
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 San Marcos's scale — its 9a band and its 289-day season. Your yard writes its own version of San Marcos'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 San Marcos’s own scale
6 of the readings below were taken at San Marcos's own scale — the 25,555 acres it covers and 345 documented sites around it; 5 are borrowed from a wider read, named and linked below.
Measured here
- San Marcos's own USDA hardiness band, zones 9aUSDA PHZM 2023
- 345 documented contamination sites on the federal record near San Marcos, the closest Underground Storage Tanks record about 0.1 miles out from the town centreFederal environmental registers
- San Marcos's boundary and the 25,555 acres inside itUS Census TIGER/Line 2025
- Which of 1,086 plants clear zones 9a and a ~289-day seasonGrowable Ground crop-matching engine
- San Marcos sits in the Texas Blackland Prairies — not the ecoregion its county mostly readsUS EPA Level III Ecoregions
- Lanternfly survey cells around San Marcos checked, none carrying a detectionlydemapr (De Bona & Helmus), 10 km survey lattice
Inherited from a wider read
- The 28°F hard-freeze dates — San Marcos has no normal of its own, so its county's is the closest measured readfrom Hays County
- Soil character — no town-scale survey exists, so San Marcos's 25,555 acres read through its county's SSURGO summaryfrom Hays County
- Growing-degree days and winter chill — measured county-wide only, so the county page carries themfrom Hays County
- The growing challenges every Texas grower plans around — written at state scale, so they stay on the state guidefrom Texas
- Butterfly and beetle records, and the farmland pesticide estimate — all published county-widefrom Hays County
What this page can’t tell you
- The soil pH, drainage, sun hours, and frost pockets on any one lot among San Marcos's 25,555 acreswhy one lot differs from the next →
- Which side of San Marcos you're on — a low spot frosts first and a south wall warms early, and one normal is being asked to speak for all 25,555 acresreading your own microclimate →
- How close that record sits to YOUR lot — the closest Underground Storage Tanks record about 0.1 miles 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 San Marcos-wide figureread your own land →
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