Maricopa County, in Arizona, sits in USDA hardiness zone 9b — a zone band wide enough that plant choice, not possibility, is the interesting question.
Expect okra, meyer lemon, california poppy, and artichoke to be strong candidates here; the deciding factors on any one parcel stay local — soil, sun, and drainage.
Maricopa County lies within the Salt River Valley / Phoenix 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
Maricopa County holds more than one microclimate.
Soils and elevations shift across Maricopa 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 Maricopa County — soil, climate, flood, and parcel records. How we handle your address.
No card required · your full report in seconds
Maricopa County — the short answer
Maricopa County, Arizona: USDA zone 9b, about 345 days between hard freezes, across 5.9M acres.
- USDA zone
- 9b
- USDA PHZM 2023
- Last hard freeze (28°F)
- Jan 15
- NOAA 1991–2020 Climate Normals, 28°F
- First hard freeze (28°F)
- Dec 26
- NOAA 1991–2020 Climate Normals, 28°F
- Days between freezes
- ~345
- 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 9b is Maricopa County's average, not your lot's — a low corner or a tree line moves it. Against Maricopa County's 345-day season, see what your own ground reads.
Heat and winter chill in Maricopa County
Across a year, Maricopa County accumulates about 8,410 growing degree days above 50°F, about 3,651 more than the middle Arizona county — ahead of every other Arizona county. 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 506 hours below 45°F, 973 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 Maricopa County
Across Maricopa County, the ground is predominantly Aridisols, where Gilman, Gunsight, and Mohall are the most extensive named soil series. The soil is generally well drained with a loam surface. Topsoil pH runs about 7.9–8.2, moderately 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 Maricopa County
The USDA soil survey maps 60% of Maricopa County as well drained — but another 31% drains differently: 28% somewhat excessively drained, 3% excessively drained.
Gilman is the most extensive named soil at 7% of mapped acres, then Gunsight (6%) and Mohall (5%).
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 Maricopa County
Each reading below is measured for Maricopa 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 Maricopa 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 Maricopa County runs about pH 7.9–8.2, 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
MeasuredMaricopa County runs about 345 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
MeasuredMaricopa County sits in USDA hardiness zone 9b.
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 Maricopa County is in
Maricopa County sits in the Sonoran Basin and Range — EPA Level III, inside the wider North American Deserts. One consistent ecological setting across the whole county.
What Grows in Maricopa County
We scored all 1,086 plants against Maricopa County's own USDA zone 9b and its own 345-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 Maricopa County?
Usually not — gardeners here simply switch what goes in the ground as the season moves. Cool-season crops can go in from around Jan 1; tender transplants wait until two to three weeks after the last 28°F hard freeze, which lands near Jan 15 (NOAA 1991–2020 climate normals); and from midsummer, planting counts back from the first fall freeze around Dec 26 — long-season crops need about 90 days of runway, quick greens only 30. In a climate this gentle, “too late” hardly applies — the question becomes which crops prefer the cooler months ahead.
Documented around Maricopa County
Survey cells within 31 miles of Maricopa County checked for spotted lanternfly, none carrying a detection — a surveyed negative, not an absence of looking. Nearest documented record 271 miles off. What to watch for.
- Japanese beetle2 documented records
- monarch butterfly35 documented records
Sighting records, so they follow observers as much as insects.
What gets applied to farmland in Maricopa County
USGS estimates 101,464 lb of Glyphosate on Maricopa County farmland in 2019, its largest by weight, ahead of Malathion (30,498 lb) and Metolachlor-s (16,575 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 Maricopa County — and how to grow with it.
We checked the federal record across Maricopa County — 11,547 documented sites across 7 of the 9 source types we track.
The most significant on record: 48 Superfund sites. Sites tracked in EPA's Superfund program — from assessment-stage CERCLIS entries to confirmed National Priorities List cleanup sites.
Maricopa 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 Maricopa County
Closest first, across Maricopa County. Listing isn't leaking, and distance isn't exposure.
- C-01-03 13DABNitrate · 0.6 mi
- C-01-03 13ABANitrate · 0.6 mi
- C-01-02 17CBANitrate · 0.9 mi
- C-01-03 13CDCNitrate · 1.2 mi
- BALES CATTLE COMPANYUnderground Storage Tanks · 1.3 mi
- C-01-03 14DDD1Nitrate · 1.5 mi
- 56874Nitrate · 1.6 mi
- C-01-02 06DBBNitrate · 1.7 mi
- C-01-02 19CCCNitrate · 1.7 mi
- C-01-03 01ADDNitrate · 1.8 mi
- C-01-02 06ADDNitrate · 2.0 mi
- C-01-03 02DADNitrate · 2.0 mi
6 more sites are on the record inside the same radius. See them on the map
Measured from Maricopa 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 Maricopa County.
Sources Checked
across Maricopa County
Severity Distribution
across Maricopa County
Highest-Severity Sites
A note from Gnorman
What an experienced grower watches for around here
In and around Maricopa County, Nitrate runs higher than the national average — 3,302 sites across Maricopa County. 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.
Test well water for nitrate if you rely on a private well for irrigation (EPA standard: 10 mg/L).
Check your specific parcel in Maricopa 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 Maricopa County average
Your land is one point inside Maricopa County
Everything above resolves to Maricopa 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 Maricopa County Average
Maricopa County Average
- ●USDA Zones 9b, averaged across Maricopa County
- ●One soil character for all of Maricopa County
- ●Frost dates read at Maricopa County's scale: Jan 15 to Dec 26
YOUR Parcel
- ✓Your exact zone, not Maricopa County's 9b
- ✓Your SSURGO soil type & pH
- ✓Your sun exposure, cast in 3D
See MY Growing Report
Read your parcel in Maricopa County
Pull a site-specific report for your exact address in Maricopa County, Arizona — soil, sun, drainage, frost risk, and scored plant recommendations.
Three things about your lot that Maricopa County averages can't show:
We read public map data around Maricopa County — soil, climate, flood, and parcel records. How we handle your address.
25+ data sources read at your address, not the Maricopa County average
How we know this about Maricopa 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 Maricopa County carries no record of its own, the figure is inherited and labelled — the resolution ledger below names each.
Common questions about Maricopa County
When does frost risk typically end in Maricopa County?
The last hard freeze (28°F) in Maricopa County typically lands around Jan 15, 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 5.
How long is the growing season in Maricopa County?
Measured between 28°F hard freezes, Maricopa County sees about 345 frost-free days — roughly Jan 15 through Dec 26, per NOAA 1991–2020 climate normals. Tender crops work a shorter one: nearer Feb 5 to Dec 12, about 310 days.
Is the soil safe to grow vegetables in Maricopa County?
The federal record around Maricopa County runs heavier than most — 11,547 documented sites, mostly Underground Storage Tanks entries (4,858), the nearest Nitrate record about 0.6 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 Maricopa County's scale — its 9b band and its 345-day season. Your yard writes its own version of Maricopa 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 Maricopa County’s own scale
9 of the readings below were taken at Maricopa County's own scale — its own ~345-day span between 28°F freezes, the 3 most extensive soil series mapped here and 11,547 documented sites inside its boundary; one is borrowed from a wider read, named and linked below.
Measured here
- Maricopa County's own USDA hardiness band, zones 9bUSDA PHZM 2023
- Maricopa County's own 28°F hard-freeze dates and its ~345-day span between themNOAA 1991–2020 Climate Normals
- The soil order, drainage, surface pH, and the 3 most extensive named soil series mapped in Maricopa CountyUSDA NRCS SSURGO
- 11,547 documented contamination sites inside the county boundary, distance-sorted from its center — the closest Nitrate record about 0.6 miles outFederal environmental registers
- Maricopa County's boundary and the 5,889,288 acres inside itUS Census TIGER/Line 2025
- Which of 1,086 plants clear zones 9b and a ~345-day seasonGrowable Ground crop-matching engine
- Maricopa County sitting wholly inside the Sonoran Basin and RangeUS EPA Level III Ecoregions
- Open occurrence records documented in Maricopa County for 2 tracked speciesGBIF derived datasets (CC0 / CC BY 4.0)
- Which agricultural compounds go onto Maricopa 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 Maricopa County — the ~345 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 Maricopa County's 5,889,288 acreswhy one lot differs from the next →
- Which of those 11,547 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 Maricopa Countyread your own land →