Pima County, in Arizona, sits in USDA hardiness zone 9a — a zone band wide enough that plant choice, not possibility, is the interesting question.
On paper, artichoke, fig, california poppy, and cabbage all suit these conditions — on the ground, soil, sun, and drainage make the final call.
Pima County lies within Sonoita / Elgin and the Sonoran Desert — a regional growing area with its own character.
Grounded in USDA PHZM 2023 · Growable Ground suitability scoring · NOAA 1991–2020 Climate Normals
Pima County holds more than one microclimate.
Soils and elevations shift across Pima County, 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 Pima County — soil, climate, flood, and parcel records. How we handle your address.
No card required · your full report in seconds
Pima County — the short answer
Pima County, Arizona: USDA zone 9a, about 313 days between hard freezes, across 5.9M acres.
- USDA zone
- 9a
- USDA PHZM 2023
- Last hard freeze (28°F)
- Feb 3
- NOAA 1991–2020 Climate Normals, 28°F
- First hard freeze (28°F)
- Dec 13
- NOAA 1991–2020 Climate Normals, 28°F
- Days between freezes
- ~313
- NOAA 1991–2020 Climate Normals, 28°F
- County area
- 5.9M 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 Pima County's average, not your lot's — a low corner or a tree line moves it. Against Pima County's 313-day season, see what your own ground reads.
Heat and winter chill in Pima County
Across a year, Pima County accumulates about 6,165 growing degree days above 50°F, about 1,406 more than the middle Arizona county — ahead of 10 of Arizona’s 15 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 738 hours below 45°F, 741 fewer than the Arizona middle of 1,479. 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 Pima County
Across Pima County, the ground is predominantly Aridisols, where Mohall, Hayhook, and Bucklebar are the most extensive named soil series. The soil is generally well drained with a sandy loam surface. Topsoil pH runs about 7.2–7.9, slightly alkaline. Rainfall drains through hydrologic group D soils.
Soil order
Aridisols
Drainage
Well drained
Hydric soils
0%
Soil still varies lot by lot — soil types explained.
How the ground varies across Pima County
The USDA soil survey maps 87% of Pima County as well drained — but another 10% drains differently: 8% somewhat excessively drained, 2% excessively drained.
Mohall is the most extensive named soil at 4% of mapped acres, then Hayhook (4%) and Bucklebar (3%).
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 Pima County
Each reading below is measured for Pima County itself — here is what it means for a garden here, and the move an experienced grower makes about it.
Drainage
MeasuredThe dominant soils across Pima County are well drained, in hydrologic group D — ground that drains quickly.
The upside is soil you can work early in spring and roots that never drown; the cost is that fast-draining ground dries out fast and leaches nutrients away before plants can use them.
Work in compost and mulch to hold moisture and feed, and water more often in short doses than deep and rarely.
USDA NRCS SSURGO
Surface pH
MeasuredTopsoil across Pima County runs about pH 7.2–7.9, on the alkaline side.
Many vegetables cope, but acid-lovers like blueberries struggle, and iron and manganese lock up above about pH 7.5 — leaves yellow between the veins even in rich soil.
Elemental sulfur and generous organic matter lower pH slowly for the beds that need it; test first so you add only what the soil actually calls for.
USDA NRCS SSURGO
Season length
MeasuredPima County runs about 313 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
MeasuredPima County 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 Pima County is in
Pima County spans 2 EPA Level III ecoregions — Sonoran Basin and Range (77%) and Madrean Archipelago (23%). 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 Pima County
We scored all 1,086 plants against Pima County's own USDA zone 9a and its own 313-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 Arizona profile.
Is it too late to plant in Pima County?
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 6; tender transplants wait until two to three weeks after the last 28°F hard freeze, which lands near Feb 3 (NOAA 1991–2020 climate normals); and from midsummer, planting counts back from the first fall freeze around Dec 13 — 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 Pima County
- monarch butterfly69 documented records
Sighting records, so they follow observers as much as insects.
What gets applied to farmland in Pima County
USGS estimates 35,580 lb of Glyphosate on Pima County farmland in 2019, its largest by weight, ahead of 2,4-d (5,821 lb) and Dicamba (2,906 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 Pima County — and how to grow with it.
We checked the federal record across Pima County — 5,043 documented sites across 7 of the 9 source types we track.
The most significant on record: 22 Superfund sites. Sites tracked in EPA's Superfund program — from assessment-stage CERCLIS entries to confirmed National Priorities List cleanup sites.
Pima County 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 Pima County
Closest first, across Pima County. Listing isn't leaking, and distance isn't exposure.
- Hercules & Monarch MineMining · 2.6 mi
- Blue Jay GroupMining · 3.3 mi
- Goon ProspectMining · 3.3 mi
- La EsperanzaMining · 3.3 mi
- Silver Lead GroupMining · 3.3 mi
- LodeMining · 3.3 mi
- Lead King Wantahela 1-4Mining · 3.3 mi
- IronwoodMining · 3.3 mi
- Old VerdeMining · 3.3 mi
- Arcade MineMining · 3.3 mi
- Homestake MineMining · 3.3 mi
- Stump MineMining · 3.3 mi
6 more sites are on the record inside the same radius. See them on the map
Measured from Pima County'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 Pima County.
Severity Distribution
across Pima County
Highest-Severity Sites
A note from Gnorman
What an experienced grower watches for around here
In and around Pima County, two things run higher than the national average across Pima County — Mining (1,285 sites) and Nitrate (1,588 sites). That's not a problem with your land — it's information about it.
Mining: Mining sites — both historic and active — can leach heavy metals (arsenic, lead, cadmium, mercury) into soil and water for centuries after operations cease.
Nitrate: Nitrate contamination primarily comes from agricultural fertilizer runoff and failing septic systems.
Test soil for heavy metals (lead, arsenic, cadmium, mercury) — this is essential near any mining site.
Test well water for nitrate if you rely on a private well for irrigation (EPA standard: 10 mg/L).
Check your specific parcel in Pima County
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 Pima County average
Your land is one point inside Pima County
Everything above resolves to Pima County as a whole — one PHZM band and one county frost record, read across 5.9M 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 Pima County Average
Pima County Average
- ●USDA Zones 9a, averaged across Pima County
- ●One soil character for all of Pima County
- ●Frost dates read at Pima County's scale: Feb 3 to Dec 13
YOUR Parcel
- ✓Your exact zone, not Pima County's 9a
- ✓Your SSURGO soil type & pH
- ✓Your sun exposure, cast in 3D
See MY Growing Report
Read your parcel in Pima County
Pull a site-specific report for your exact address in Pima County, Arizona — soil, sun, drainage, frost risk, and scored plant recommendations.
Three things about your lot that Pima County averages can't show:
We read public map data around Pima County — soil, climate, flood, and parcel records. How we handle your address.
25+ data sources read at your address, not the Pima County average
How we know this about Pima County
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 Pima County carries no record of its own, the figure is inherited and labelled — the resolution ledger below names each.
Common questions about Pima County
When does frost risk typically end in Pima County?
The last hard freeze (28°F) in Pima County typically lands around Feb 3, 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 Feb 24.
How long is the growing season in Pima County?
Measured between 28°F hard freezes, Pima County sees about 313 frost-free days — roughly Feb 3 through Dec 13, per NOAA 1991–2020 climate normals. Tender crops work a shorter one: nearer Feb 24 to Nov 29, about 278 days.
Is the soil safe to grow vegetables in Pima County?
The federal record around Pima County runs heavier than most — 5,043 documented sites, mostly Nitrate entries (1,588), the nearest Mining record about 2.6 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 Pima County's scale — its 9a band and its 313-day season. Your yard writes its own version of Pima County'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 Arizona's frost window, season length, and soil profile against the plant's real requirements.
What this page reads at Pima County’s own scale
9 of the readings below were taken at Pima County's own scale — its own ~313-day span between 28°F freezes, the 3 most extensive soil series mapped here and 5,043 documented sites inside its boundary; one is borrowed from a wider read, named and linked below.
Measured here
- Pima County's own USDA hardiness band, zones 9aUSDA PHZM 2023
- Pima County's own 28°F hard-freeze dates and its ~313-day span between themNOAA 1991–2020 Climate Normals
- The soil order, drainage, surface pH, and the 3 most extensive named soil series mapped in Pima CountyUSDA NRCS SSURGO
- 5,043 documented contamination sites inside the county boundary, distance-sorted from its center — the closest Mining record about 2.6 miles outFederal environmental registers
- Pima County's boundary and the 5,880,758 acres inside itUS Census TIGER/Line 2025
- Which of 1,086 plants clear zones 9a and a ~313-day seasonGrowable Ground crop-matching engine
- The 2 ecoregions Pima County spans, Sonoran Basin and Range the largestUS EPA Level III Ecoregions
- Open occurrence records documented in Pima County for a tracked speciesGBIF derived datasets (CC0 / CC BY 4.0)
- Which agricultural compounds go onto Pima County farmland, and roughly how muchUSGS NAWQA EPest county estimates
Inherited from a wider read
- The growing challenges every Arizona grower plans around — written at state scale, so they stay on the state guidefrom Arizona
What this page can’t tell you
- How the season shifts across Pima County — the ~313 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 Pima County's 5,880,758 acreswhy one lot differs from the next →
- Which of those 5,043 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 Pima Countyread your own land →