The Imperial Valley spans USDA hardiness zone 9b — a zone band wide enough that plant choice, not possibility, is the interesting question.
Farmed almost entirely below sea level and watered by the Colorado River through the All-American Canal, the Imperial Valley grows when much of the country can't: Imperial County averages a 344-day frost-free season, so mild, near-frostless winters turn the valley floor into a winter-vegetable powerhouse of lettuce, carrots, onions, and broccoli, while blistering summers favor dates, alfalfa, and heat-loving grasses. Unlike the saguaro-and-palo-verde uplands of the broader Sonoran Desert, here the growing calendar flips — winter is the prime season and summer is the one to plan around. Growers here do well with tomato, artichoke, fig, and california poppy — with the usual caveat that any single yard's soil, sun, and drainage cast the deciding vote.
The Imperial Valley spans California.
Your yard isn't all of the Imperial Valley.
The Imperial Valley 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 Imperial Valley — soil, climate, flood, and parcel records. How we handle your address.
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The Imperial Valley — the short answer
The Imperial Valley: USDA zones 9b, 344 frost-free days, in California.
- USDA zones
- 9b
- USDA PHZM 2023, aggregated over the footprint
- Frost-free season
- 344 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 Imperial Valley
Plants matched to the Imperial Valley'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 Imperial Valley
Plants the USDA PLANTS Database documents as native and present in this region’s state, kept only where the published hardiness range meets the Imperial Valley’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 Imperial Valley
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 Entisols, at 96% of mapped acres, followed by Aridisols (4%). The most extensive named soils are Imperial, Indio, and Rositas.
73% of those acres are moderately well drained, and another 15% well drained, 7% somewhat excessively drained. Topsoil pH runs 8.2–8.2 in that county’s own record.
Soil order
Entisols
Drainage
Moderately well drained
Topsoil pH
8.2–8.2
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. soil types explained.
USDA NRCS SSURGO via Soil Data Access
What this means for growing in the Imperial Valley
The soil survey reads this ground county by county, and the readings above are those records summed across the Imperial Valley. Here is what they mean for a garden here — and the move an experienced grower makes about each one.
Drainage
From county records73% of the mapped acres across the Imperial Valley are moderately well drained — roughly the middle of the drainage range. That is area-weighted across its one mapped county.
This is close to the middle most vegetables prefer: it holds enough water to carry a crop between rains without staying waterlogged. The catch is that a wet spring or a low corner can still tip it soggy.
Plant on the site as-is for most crops, but keep the lowest, slowest-draining beds for moisture-tolerant plantings.
USDA NRCS SSURGO
Surface pH
From county recordsTopsoil across the Imperial Valley runs pH 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 Imperial Valley — and how to grow with it.
Across the Imperial Valley's 1 county the federal record holds 1,452 documented sites, mostly Brownfields (992), Nitrate (288) and Underground Storage Tanks (85). The heaviest single county is Imperial County, with 1,452.
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 Imperial Valley to see which records sit where you actually grow.
Sources Checked
Summed across the county in the Imperial Valley
A note from Gnorman
What an experienced grower watches for around here
In and around the Imperial Valley, two things run higher than the national average across the county in the Imperial Valley — Brownfields (992 sites) and PFAS (12 sites). Knowing it is half the work — and it's nothing a thoughtful grower can't plan for.
Brownfields: Brownfield sites are former commercial or industrial properties where legacy soil contamination (heavy metals, PAHs, petroleum compounds) may persist.
PFAS: PFAS (per- and polyfluoroalkyl substances) are called "forever chemicals" because they do not biodegrade.
Check EPA brownfield remediation status — many sites have completed cleanup with institutional controls.
Test irrigation water source — this is the primary pathway for PFAS to reach garden crops.
Sources: EPA, USGS — 1.8M documented sites tracked nationwide across 9 federal source types.
Your land is one point inside the Imperial Valley
Everything above resolves to the Imperial Valley 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 Imperial Valley Average
Imperial Valley Average
- ●USDA Zones 9b, averaged across Imperial Valley
- ●One soil character for all of Imperial Valley
- ●State-average frost dates
YOUR Parcel
- ✓Your exact zone, not Imperial Valley's 9b
- ✓Your SSURGO soil type & pH
- ✓Your sun exposure, cast in 3D
See MY Growing Report
Read your parcel in the Imperial Valley
Pull a site-specific report for your exact address in the Imperial Valley — soil, sun, drainage, frost risk, contamination, and scored plant recommendations.
Three things about your lot that Imperial Valley averages can't show:
We read public map data around The Imperial Valley — soil, climate, flood, and parcel records. How we handle your address.
25+ data sources read at your address, not the Imperial Valley average
How we know this about the Imperial Valley
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 Imperial Valley
What hardiness zone is the Imperial Valley?
The Imperial Valley 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 Imperial Valley?
The Imperial Valley's conditions suit plants such as Tomato, Artichoke, Fig, California Poppy, Rosemary, Olive. 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 Imperial Valley defined?
The Imperial Valley 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 Imperial Valley cover?
The Imperial Valley spans 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 Sonoran Desert share at least one state with the Imperial Valley. 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 Imperial Valley’s own scale
5 of the readings below were taken at the Imperial Valley's own scale — the zone 9b band across its footprint and 1,452 documented federal contamination records across its one county, 1,452 of them in Imperial 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 — 1,452 documented federal contamination records across its one county, 1,452 of them in Imperial County aloneEPA, USGS and USDA federal site records
- The soil order mix across the footprint — 96% Entisols, topsoil pH 8.2–8.2, 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 California
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 Imperial Valley
State growing guides
Counties in this region
Other growing regions across 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.
A warm desert of saguaro and palo verde with mild winters that allow desert citrus, dates, and prickly pear alongside intensive irrigated gardening.