The Salt River Valley / Phoenix spans USDA hardiness zone 9b — enough range to grow cool-season vegetables, hardy fruit, and warm-season crops that mature before the first hard frost.
The Salt River Valley isn't the Sonoran Desert averaged out — it's the hottest, longest-season heart of it. Scoped to Maricopa County alone, the numbers sharpen to a solid 9b and about 345 frost-free days (last frost near mid-January, first near the year's end; county_data.json) — the top of Arizona's range, and well past the ~313-day Tucson edge that drags the broader desert's average down. This is the valley the Hohokam first canaled and the Salt River Project still irrigates today: a year-round warm-season floor where the real question isn't whether your crops survive winter but whether they survive July. Frost is barely a factor here; the constraint that defines Phoenix growing is the urban heat island — nights that don't cool, and a summer that rewards afternoon shade, heat-tolerant varieties, and a fall-through-spring planting calendar over a conventional one. Crops well matched to these conditions include jalapeno, palo verde, date palm, and prickly pear — though what thrives on any one site still turns on its specific soil, sun, and drainage.
The Salt River Valley / Phoenix spans Arizona.
Your yard isn't all of the Salt River Valley / Phoenix.
The Salt River Valley / Phoenix spans USDA zones 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 Salt River Valley / Phoenix — soil, climate, flood, and parcel records. How we handle your address.
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The Salt River Valley / Phoenix — the short answer
The Salt River Valley / Phoenix: USDA zones 9b, 345 frost-free days, in Arizona.
- USDA zones
- 9b
- USDA PHZM 2023, aggregated over the footprint
- Frost-free season
- 345 days
- NOAA Regional Climate Centers ACIS, 1991–2020
- Counties
- 1
- US Census TIGER/Line 2025
- Region type
- County cluster
- 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. Where a region publishes no measured season, no season figure is shown.
Hardiness Zone Range
What Grows in the Salt River Valley / Phoenix
Plants matched to the Salt River Valley / Phoenix's USDA zones 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 Salt River Valley / Phoenix
Plants the USDA PLANTS Database documents as native and present in this region’s state, kept only where the published hardiness range meets the Salt River Valley / Phoenix’s USDA zones 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 Salt River Valley / Phoenix
The USDA soil survey maps this ground county by county. These are those records weighted by land area across one member county — this region’s own profile, not a state figure.
The ground is predominantly Aridisols, at 69% of mapped acres, followed by Entisols (31%). Three 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 Gilman, Gunsight, and Mohall.
60% of those acres are well drained, and another 28% somewhat excessively drained, 3% excessively drained. Topsoil pH runs 7.9–8.2 in that county’s own record.
Soil order
Aridisols
Drainage
Well drained
Topsoil pH
7.9–8.2
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. soil types explained.
USDA NRCS SSURGO via Soil Data Access
What this means for growing in the Salt River Valley / Phoenix
The soil survey reads this ground county by county, and the readings above are those records summed across the Salt River Valley / Phoenix. Here is what they mean for a garden here — and the move an experienced grower makes about each one.
Drainage
From county records60% of the mapped acres across the Salt River Valley / Phoenix are well drained — ground that drains quickly. That is area-weighted across its one mapped county.
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 Salt River Valley / Phoenix runs pH 7.9–8.2 — alkaline in the one record covering it.
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 Salt River Valley / Phoenix — and how to grow with it.
Across the Salt River Valley / Phoenix's 1 county the federal record holds 11,547 documented sites, mostly Underground Storage Tanks (4,858), Nitrate (3,302) and Brownfields (2,379). 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 Salt River Valley / Phoenix to see which records sit where you actually grow.
Sources Checked
Summed across the county in the Salt River Valley / Phoenix
A note from Gnorman
What an experienced grower watches for around here
In and around the Salt River Valley / Phoenix, Nitrate runs higher than the national average — 3,302 sites across the county in the Salt River Valley / Phoenix. Knowing it is half the work — and it's nothing a thoughtful grower can't plan for.
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).
Sources: EPA, USGS — 1.8M documented sites tracked nationwide across 9 federal source types.
Your land is one point inside the Salt River Valley / Phoenix
Everything above resolves to the Salt River Valley / Phoenix as a whole — a footprint spanning USDA zones 9b. Your parcel sits in exactly one of them. 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 Salt River Valley / Phoenix Average
Salt River Valley / Phoenix Average
- ●USDA Zones 9b, averaged across Salt River Valley / Phoenix
- ●One soil character for all of Salt River Valley / Phoenix
- ●State-average frost dates
YOUR Parcel
- ✓Your exact zone, not Salt River Valley / Phoenix's 9b
- ✓Your SSURGO soil type & pH
- ✓Your sun exposure, cast in 3D
See MY Growing Report
Read your parcel in the Salt River Valley / Phoenix
Pull a site-specific report for your exact address in the Salt River Valley / Phoenix — soil, sun, drainage, frost risk, contamination, and scored plant recommendations.
Three things about your lot that Salt River Valley / Phoenix averages can't show:
We read public map data around The Salt River Valley / Phoenix — soil, climate, flood, and parcel records. How we handle your address.
25+ data sources read at your address, not the Salt River Valley / Phoenix average
How we know this about the Salt River Valley / Phoenix
The boundary: a cluster of neighboring counties. 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 Salt River Valley / Phoenix
What hardiness zone is the Salt River Valley / Phoenix?
The Salt River Valley / Phoenix spans USDA hardiness zones 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.
What grows well in the Salt River Valley / Phoenix?
The Salt River Valley / Phoenix's conditions suit plants such as Jalapeno, Palo Verde, Date Palm, Prickly Pear, Citrus. 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 Salt River Valley / Phoenix defined?
The Salt River Valley / Phoenix is defined here as a curated cluster of 1 neighboring counties that share a growing character. Growing regions have no official boundary, so this footprint is our published one — every county in it is named on this page.
Which states does the Salt River Valley / Phoenix cover?
The Salt River Valley / Phoenix spans Arizona. Each state's full growing guide is linked on this page.
What other growing regions cover the same states?
Sonoran Desert, Sonoita / Elgin, Lower Colorado River Corridor, White Mountains (Eastern Arizona), Willcox AVA, and Flagstaff & San Francisco Peaks High Country share at least one state with the Salt River Valley / Phoenix. 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 Salt River Valley / Phoenix’s own scale
5 of the readings below were taken at the Salt River Valley / Phoenix's own scale — the zone 9b band across its footprint and 11,547 documented federal contamination records across its one county, 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 9b aggregated across the footprint's one countyUSDA PHZM 2023
- The boundary itself — the 1 county this region is curated fromGrowable Ground subregion registry
- The growing character that makes this region distinct from the states it crossesGrowable Ground subregion registry
- The federal contamination record over the whole footprint — 11,547 documented federal contamination records across its one county, 11,547 of them in Maricopa County aloneEPA, USGS and USDA federal site records
- The soil order mix across the footprint — 69% Aridisols, topsoil pH 7.9–8.2, area-weighted across its one mapped countyUSDA NRCS SSURGO
Inherited from a wider read
- The candidate plant list — its state's curated sets, merged and filtered to zones 9bfrom Arizona
What this page can’t tell you
- Frost dates — they swing too far across a footprint this size to quote as one regional numberfrost 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 Salt River Valley / Phoenix
State growing guides
Counties in this region
Other growing regions across Arizona
A warm desert of saguaro and palo verde with mild winters that allow desert citrus, dates, and prickly pear alongside intensive irrigated gardening.
Defined by the TTB's Sonoita American Viticultural Area (27 CFR § 9.97) — Arizona's first AVA, established in 1984 — this high-desert grassland spans Cochise, Pima, and Santa Cruz counties across USDA zones 8a to 9a, where the frost-free season runs roughly 264 to 313 days.
The river towns from Bullhead City to Parker — essentially frost-free 9a-10a bottomland where citrus and winter gardens run while the Mohave high desert a half-hour up the grade freezes.
Arizona's high green country — at the White Mountain towns the committed record reads 6a-7a with a 145-176-day season, mountain gardening closer to Colorado than to the desert two hours down the hill.
Established by the TTB in 2016 across parts of Cochise and Graham Counties in southeastern Arizona, the Willcox AVA spans USDA hardiness zones 8a to 8b with a roughly 264-to-266-day frost-free season.
The cold antithesis of desert Arizona: a ponderosa-pine plateau near 7,000 ft where Flagstaff sits in USDA zone 6a and Bellemont drops to 5b, with only about 150 frost-free days — roughly mid-May last frost to mid-October first frost (Coconino County, api/data/county_data.json). The statewide "zone 9b, near-frost-free" framing is actively wrong here; growers plan around snow, a short cool-season window, and hard frost dates instead of citrus and dates.