The Sonoran Desert spans USDA hardiness zones 9a-9b — a range where zone-matched perennials and frost-aware annual timing set what succeeds.
A warm desert of saguaro and palo verde with mild winters that allow desert citrus, dates, and prickly pear alongside intensive irrigated gardening. Reliable performers under these conditions include jalapeno, tomato, artichoke, and palo verde; what your own ground favors still comes down to its soil, sun, and drainage.
The Sonoran Desert spans Arizona and California. Its footprint follows the EPA Level III ecoregion boundary; the counties linked below are representative of the region, not an exhaustive list.
Your yard isn't all of the Sonoran Desert.
The Sonoran Desert spans USDA zones 9a-9b, but your parcel sits in exactly one — and slope, tree cover, and low spots nudge it further. 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 Sonoran Desert — soil, climate, flood, and parcel records. How we handle your address.
No card required · your full report in seconds
The Sonoran Desert — the short answer
The Sonoran Desert: USDA zones 9a-9b, 313–345 frost-free days depending where in it you stand, across 2 states.
- USDA zones
- 9a-9b
- USDA PHZM 2023, aggregated over the footprint
- Shortest season here
- 313 days
- NOAA Regional Climate Centers ACIS, 1991-2020 — Pima County
- Counties
- 6
- US Census TIGER/Line 2025
- Region type
- EPA ecoregion
- Growable Ground growing-region registry
Region boundary: Growable Ground growing-region registry — curated county clusters, EPA Level III ecoregions, and town clusters drawn finer than any county. The season figure is this region's own record, measured across its 6 member counties, not a state or national average.
Hardiness Zone Range
The Sonoran Desert is not one growing season
One answer for the Sonoran Desert averages 6 counties whose growing seasons are 32 days apart — from 313 frost-free days in Pima County to 345 in Maricopa County. That is the same region, measured the same way, in the same years. Which end of it your land sits nearer decides what finishes before the first hard freeze.
The middle half of 6 counties runs 319–345 days, with a median of 336 days — a 32-day span end to end.
Measured across 6 member counties, each carrying its own 28°F normal. NOAA Regional Climate Centers ACIS, 1991-2020. A member with no own record is absent from the range rather than counted as zero — nothing here is interpolated to the region. Your own site sits somewhere inside this range; a parcel report resolves where.
What Grows in the Sonoran Desert
All 2 of the plants below that publish a season requirement clear even Pima County’s 313 frost-free days — so on season alone, this grid works at both ends of the region. The 32-day spread still decides how far past this list you can push, and how early you can start.
Plants matched to the Sonoran Desert's USDA zones 9a-9b, ordered by how much hardiness margin each has across the region — the ones with room to spare at both ends of this band lead. Each links to its full growing profile.
Native Plants of the Sonoran Desert
Plants the USDA PLANTS Database documents as native and present in all 2 states this region crosses, kept only where the published hardiness range meets the Sonoran Desert’s USDA zones 9a-9b — closest range match first. Presence is recorded by state, so a plant can be documented across the state and still be scarce in your corner of the region.
The ground across the Sonoran Desert
The USDA soil survey maps this ground county by county. These are those records weighted by land area across six member counties — this region’s own profile, not a state figure.
The ground is predominantly Aridisols, at 65% of mapped acres, followed by Entisols (34%) and Mollisols (1%). Five soil orders appear somewhere inside the footprint, which is the honest reason a regional soil answer only goes so far. The most extensive named soils are Imperial, Gunsight, and Mohall.
59% of those acres are well drained, and another 24% somewhat excessively drained, 8% moderately well drained. Topsoil pH runs 7.2–8.2 between the lowest and the highest county on record.
Soil order
Aridisols
Drainage
Well drained
Topsoil pH
7.2–8.2
Hydric soils
0%
Soil changes across a driveway, so which of these your own ground sits on is a parcel question rather than a regional one. Pinal County holds the most wetland ground here, at 0% — soil types explained.
USDA NRCS SSURGO via Soil Data Access
What this means for growing in the Sonoran Desert
The soil survey reads this ground county by county, and the readings above are those records summed across the Sonoran Desert. Here is what they mean for a garden here — and the move an experienced grower makes about each one.
Drainage
From county records59% of the mapped acres across the Sonoran Desert are well drained — ground that drains quickly. That is area-weighted across all six of its mapped counties.
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
From county recordsTopsoil across the Sonoran Desert runs pH 7.2–8.2 — alkaline in all six of them.
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
Safe to Grow Here?
What the federal record shows across the Sonoran Desert — and how to grow with it.
Across the Sonoran Desert's 6 counties the federal record holds 22,087 documented sites, mostly Underground Storage Tanks (7,310), Nitrate (6,688) and Brownfields (4,183). The heaviest single county is Maricopa County, with 11,547.
That is a regional count, not a reading of any one lot — proximity to a documented site is information, not a diagnosis. Open the map outlined to the Sonoran Desert to see which records sit where you actually grow.
Sources Checked
Summed across the 6 counties in the Sonoran Desert
A note from Gnorman
What an experienced grower watches for around here
In and around the Sonoran Desert, two things run higher than the national average across the 6 counties in the Sonoran Desert — Mining (2,778 sites) and Nitrate (6,688 sites). Knowing it is half the work — and it's nothing a thoughtful grower can't plan for.
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).
Sources: EPA, USGS — 1.8M documented sites tracked nationwide across 9 federal source types.
Your land is one point inside the Sonoran Desert
Everything above resolves to the Sonoran Desert as a whole — a footprint whose own counties record seasons 32 days apart, and hardiness across zones 9a-9b. Your parcel sits at one point in that range, not in the middle of it. 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 region 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 regional average.
Your Lot vs the Sonoran Desert Average
Sonoran Desert Average
- ●USDA Zones 9a-9b, averaged across Sonoran Desert
- ●One soil character for all of Sonoran Desert
- ●State-average frost dates
YOUR Parcel
- ✓Your exact zone, not Sonoran Desert's 9a-9b
- ✓Your SSURGO soil type & pH
- ✓Your sun exposure, cast in 3D
See MY Growing Report
Read your parcel in the Sonoran Desert
Pull a site-specific report for your exact address in the Sonoran Desert — soil, sun, drainage, frost risk, contamination, and scored plant recommendations.
Three things about your lot that Sonoran Desert averages can't show:
We read public map data around The Sonoran Desert — soil, climate, flood, and parcel records. How we handle your address.
25+ data sources read at your address, not the Sonoran Desert average
How we know this about the Sonoran Desert
The boundary: an EPA Level III ecoregion (an area sharing climate, soils, and vegetation). Growing regions have no official boundary, so this footprint is our published one, and every figure on this page was measured over the counties inside it rather than borrowed from the state around it.
The datasets: hardiness from the USDA ARS Plant Hardiness Zone Map 2023, aggregated across the footprint; the growing season from NOAA Regional Climate Centers ACIS 1991–2020 28°F normals, read at each member’s own record; boundaries from US Census TIGER/Line 2025; the contamination record from the federal sources named in that beat above; the soil from the USDA NRCS SSURGO survey, read at each member county’s own record and weighted to this footprint by land area. Where a member carries no record of its own, it is absent from the figure rather than filled in.
Common questions about the Sonoran Desert
What hardiness zone is the Sonoran Desert?
The Sonoran Desert spans USDA hardiness zones 9a-9b, aggregated from the USDA Agricultural Research Service Plant Hardiness Zone Map 2023 across the region's counties. Zones reflect average annual extreme minimum temperatures from 1991–2020 data.
How long is the growing season in the Sonoran Desert?
Measured between 28°F hard freezes, the Sonoran Desert's counties mostly run 319 to 345 frost-free days, median 336 (NOAA Regional Climate Centers ACIS, 1991–2020, over 6 member counties). That 26-day spread is the honest read — no single season describes 6 counties, and each county guide below carries its own.
When does frost risk end in the Sonoran Desert?
Across the Sonoran Desert, the middle half of member counties see their last 28°F hard freeze between Jan 16 and Jan 28 (median Jan 21), and their first fall freeze between Dec 14 and Dec 26. Those are hard freezes, not the last light frost: tender transplants wait for about Feb 11, and elevation decides which end of a 12-day spread you garden in.
What grows well in the Sonoran Desert?
The Sonoran Desert's conditions suit plants such as Jalapeno, Tomato, Artichoke, Palo Verde, Date Palm, Prickly Pear. What actually thrives on any one site still turns on its specific soil, sun, and drainage — we score each plant against the real conditions at your address.
How is the Sonoran Desert defined?
The Sonoran Desert's footprint follows an EPA Level III ecoregion — a boundary drawn where climate, soils, and vegetation actually change rather than where a state line falls. It covers 6 counties, and the counties linked on this page are representative of the region, not an exhaustive list.
Which states does the Sonoran Desert cover?
The Sonoran Desert spans Arizona and California. Each state's full growing guide is linked on this page.
What other growing regions cover the same states?
Pacific Northwest, California Central Valley, Sacramento Valley, San Joaquin Valley, Sierra Nevada Foothills, and California Delta share at least one state with the Sonoran Desert. Growing regions overlap and interlock — a single address can sit inside more than one, which is why the precise read is always the parcel, not the region.
What this page reads at the Sonoran Desert’s own scale
6 of the readings below were taken at the Sonoran Desert's own scale — the zone 9a-9b band across its footprint, a median 336-day season across its 6 counties and 22,087 documented federal contamination records across its 6 counties, 11,547 of them in Maricopa County alone; one is borrowed from a wider read, named and linked below.
Measured here
- The USDA hardiness band 9a-9b aggregated across all 6 counties in the footprintUSDA PHZM 2023
- The boundary itself — the EPA Level III ecoregion its 6 counties sit inside, drawn where climate and soils changeEPA Level III Ecoregions
- The growing character that makes this region distinct from the states it crossesGrowable Ground subregion registry
- The 28°F season across the footprint — the middle half of its 6 counties run 319 to 345 frost-free days, median 336NOAA Regional Climate Centers ACIS, 1991-2020
- The federal contamination record over the whole footprint — 22,087 documented federal contamination records across its 6 counties, 11,547 of them in Maricopa County aloneEPA, USGS and USDA federal site records
- The soil order mix across the footprint — 65% Aridisols, topsoil pH 7.2–8.2, area-weighted across its 6 mapped countiesUSDA NRCS SSURGO
Inherited from a wider read
- The candidate plant list — all 2 member states' curated sets, merged and filtered to zones 9a-9bfrom Arizona and California
What this page can’t tell you
- Which end of the 26-day range your ground sits at — 319 days at one extreme, 345 at the other, decided mostly by elevationfrost dates explained →
- Which of those soils your own ground sits on — the survey maps them county-wide, and they change across a drivewaysoil types explained →
- The soil pH, drainage, sun hours, and frost pockets on one specific lotwhy one lot differs from the next →
Explore the Sonoran Desert
State growing guides
Representative counties
Other growing regions across Arizona and California
The maritime Northwest west of the Cascade crest — mild, wet winters and dry summers behind berries, tree fruit, and lush cool-season gardens. (Union of the west-side ecoregions.)
A vast flat alluvial trough with hot dry summers and rich soils — one of the most productive agricultural regions on earth, from almonds and stone fruit to row crops.
The cooler, wetter northern half of the Central Valley — rice, walnuts, tomatoes, and orchard fruit on rich alluvial bottomland.
The hot southern half of California's Central Valley — deep soils and intense sun behind almonds, stone fruit, grapes, and row crops at vast scale.
California's Gold Country foothills — rocky, well-drained slopes and warm days that suit wine grapes, olives, and Mediterranean orchard crops.
Where the Sacramento and San Joaquin rivers braid into a maze of levee-ringed islands, the afternoon "Delta breeze" draws cool marine air off San Francisco Bay through the Carquinez Strait — tempering the interior valley's heat and stretching the frost-free season past 330 days in the western Delta (Solano and Contra Costa counties, per county_data.json). Behind the levees lie the black organic peat and muck soils of the reclaimed islands, the ground that made this California's historic Bartlett-pear and asparagus country and now grows cool-loving Clarksburg-AVA wine grapes like Chenin Blanc. It is the one corner of the Central Valley where a maritime influence, not just the sun, sets the growing rules.