The Rio Grande Valley spans USDA hardiness zones 9b-10a — a band that supports both cool-season staples and warm-season crops chosen to fit the local frost window.
South Texas' subtropical delta along the Rio Grande — near-frost-free winters growing citrus, sugarcane, and winter vegetables. The conditions favor okra, black-eyed pea, tomato, and jalapeno, among others — though every individual site edits that list with its own soil, sun, and drainage.
The Rio Grande Valley spans Texas.
Your yard isn't all of the Rio Grande Valley.
The Rio Grande Valley spans USDA zones 9b-10a, 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 Rio Grande Valley — soil, climate, flood, and parcel records. How we handle your address.
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The Rio Grande Valley — the short answer
The Rio Grande Valley: USDA zones 9b-10a, 322–341 frost-free days, in Texas.
- USDA zones
- 9b-10a
- USDA PHZM 2023, aggregated over the footprint
- Frost-free season
- 322–341 days
- NOAA Regional Climate Centers ACIS, 1991-2020
- Counties
- 4
- 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 Rio Grande Valley
Plants matched to the Rio Grande Valley's USDA zones 9b-10a, 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 Rio Grande 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 Rio Grande Valley’s USDA zones 9b-10a — 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 Rio Grande Valley
The USDA soil survey maps this ground county by county. These are those records weighted by land area across four member counties — this region’s own profile, not a state figure.
The ground is predominantly Mollisols, at 31% of mapped acres, followed by Alfisols (26%), Inceptisols (21%) and Vertisols (11%). Six 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 McAllen, Hidalgo, and Brennan.
58% of those acres are well drained, and another 24% moderately well drained, 5% poorly drained. Topsoil pH runs 7.0–8.2 between the lowest and the highest county on record. 12% of the footprint is classed prime farmland.
Soil order
Mollisols
Drainage
Well drained
Topsoil pH
7.0–8.2
Hydric soils
10%
Soil changes across a driveway, so which of these your own ground sits on is a parcel question rather than a regional one. Cameron County holds the most wetland ground here, at 27% — soil types explained.
USDA NRCS SSURGO via Soil Data Access
What this means for growing in the Rio Grande Valley
The soil survey reads this ground county by county, and the readings above are those records summed across the Rio Grande Valley. Here is what they mean for a garden here — and the move an experienced grower makes about each one.
Drainage
From county records58% of the mapped acres across the Rio Grande Valley are well drained — ground that drains quickly. That is area-weighted across all four 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 Rio Grande Valley runs pH 7.0–8.2 — alkaline in all four 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 Rio Grande Valley — and how to grow with it.
Across the Rio Grande Valley's 4 counties the federal record holds 2,710 documented sites, mostly Underground Storage Tanks (2,139), Brownfields (426) and Toxics Release Inventory (96). The heaviest single county is Hidalgo County, with 1,441.
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 Rio Grande Valley to see which records sit where you actually grow.
Sources Checked
Summed across the 4 counties in the Rio Grande Valley
A note from Gnorman
What an experienced grower watches for around here
In and around the Rio Grande Valley, two things run higher than the national average across the 4 counties in the Rio Grande Valley — PFAS (34 sites) and Underground Storage Tanks (2,139 sites). That's not a problem with your land — it's information about it.
PFAS: PFAS (per- and polyfluoroalkyl substances) are called "forever chemicals" because they do not biodegrade.
Underground Storage Tanks: Underground storage tanks are the single most common source of soil contamination near homes and gardens.
Test irrigation water source — this is the primary pathway for PFAS to reach garden crops.
Use raised beds with imported soil — this eliminates the primary soil-contact pathway.
Sources: EPA, USGS — 1.8M documented sites tracked nationwide across 9 federal source types.
Your land is one point inside the Rio Grande Valley
Everything above resolves to the Rio Grande Valley as a whole — a footprint spanning USDA zones 9b-10a. 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 Rio Grande Valley Average
Rio Grande Valley Average
- ●USDA Zones 9b-10a, averaged across Rio Grande Valley
- ●One soil character for all of Rio Grande Valley
- ●State-average frost dates
YOUR Parcel
- ✓Your exact zone, not Rio Grande Valley's 9b-10a
- ✓Your SSURGO soil type & pH
- ✓Your sun exposure, cast in 3D
See MY Growing Report
Read your parcel in the Rio Grande Valley
Pull a site-specific report for your exact address in the Rio Grande Valley — soil, sun, drainage, frost risk, contamination, and scored plant recommendations.
Three things about your lot that Rio Grande Valley averages can't show:
We read public map data around The Rio Grande Valley — soil, climate, flood, and parcel records. How we handle your address.
25+ data sources read at your address, not the Rio Grande Valley average
How we know this about the Rio Grande 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 Rio Grande Valley
What hardiness zone is the Rio Grande Valley?
The Rio Grande Valley spans USDA hardiness zones 9b-10a, 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 Rio Grande Valley?
Measured between 28°F hard freezes, the Rio Grande Valley's counties mostly run 332 to 339 frost-free days, median 337 (NOAA Regional Climate Centers ACIS, 1991–2020, over 4 member counties). That 7-day spread is the honest read — no single season describes 4 counties, and each county guide below carries its own.
When does frost risk end in the Rio Grande Valley?
Across the Rio Grande Valley, the middle half of member counties see their last 28°F hard freeze between Jan 18 and Jan 21 (median Jan 20), and their first fall freeze between Dec 20 and Dec 23. Those are hard freezes, not the last light frost: tender transplants wait for about Feb 10, and elevation decides which end of a 3-day spread you garden in.
What grows well in the Rio Grande Valley?
The Rio Grande Valley's conditions suit plants such as Okra, Black-eyed Pea, Tomato, Jalapeno, Sweet Potato, Rosemary. 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 Rio Grande Valley defined?
The Rio Grande Valley is defined here as a curated cluster of 4 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 Rio Grande Valley cover?
The Rio Grande Valley spans Texas. Each state's full growing guide is linked on this page.
What other growing regions cover the same states?
High Plains, Piney Woods, Texas High Plains / Panhandle, Gulf Coast, Blackland Prairie, and Coastal Bend share at least one state with the Rio Grande 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 Rio Grande Valley’s own scale
6 of the readings below were taken at the Rio Grande Valley's own scale — the zone 9b-10a band across its footprint, a median 337-day season across its 4 counties and 2,710 documented federal contamination records across its 4 counties, 1,441 of them in Hidalgo County alone; one is borrowed from a wider read, named and linked below.
Measured here
- The USDA hardiness band 9b-10a aggregated across all 4 counties in the footprintUSDA PHZM 2023
- The boundary itself — the 4 counties 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 28°F season across the footprint — the middle half of its 4 counties run 332 to 339 frost-free days, median 337NOAA Regional Climate Centers ACIS, 1991-2020
- The federal contamination record over the whole footprint — 2,710 documented federal contamination records across its 4 counties, 1,441 of them in Hidalgo County aloneEPA, USGS and USDA federal site records
- The soil order mix across the footprint — 31% Mollisols, topsoil pH 7.0–8.2, area-weighted across its 4 mapped countiesUSDA NRCS SSURGO
Inherited from a wider read
- The candidate plant list — its state's curated sets, merged and filtered to zones 9b-10afrom Texas
What this page can’t tell you
- Which end of the 7-day range your ground sits at — 332 days at one extreme, 339 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 Rio Grande Valley
State growing guides
Counties in this region
Other growing regions across Texas
A semi-arid shortgrass tableland of deep soils and big sky, where wind, low rainfall, and irrigation shape dryland wheat, sorghum, and resilient gardens.
The sandy, acidic pine-and-hardwood forest belt of East Texas and western Louisiana — the humid South Central Plains, where a long frost-free season of roughly nine months favors heat- and acid-tolerant Southern gardens.
The southern, warmer anchor of the High Plains — the Llano Estacado tableland west of the Caprock Escarpment, where a longer season (frost-free days run near 227 across the Texas counties, well above the multi-state High Plains average) and deep-well Ogallala irrigation define the growing reality. This is the largest contiguous cotton patch in the world around Lubbock (Texas Co-op Power), and, west of the Caprock, the Texas High Plains AVA (TTB, 27 CFR 9.144) that grows roughly 80% of the state's wine grapes. High, flat, and semi-arid: what grows here is what deep-well water and a zone 7a-8a season can coax from it, a distinctly Texan story rather than the dryland wheat and sorghum of the northern High Plains.
The humid, near-frost-free coastal rim of the Gulf of Mexico — long seasons, sandy and alluvial soils, heat, and hurricanes shaping what thrives. (Representative coastal counties, not exhaustive.)
Here the soil, not the zone, defines the garden. The Blackland Prairie is a narrow black-clay belt tracing the I-35 corridor from Sherman through Dallas, Waco, and Temple down to Austin — built on vertisol "black gumbo" that swells sticky when wet, then cracks open as it dries. That shrink-swell clay is alkaline and slow-draining, so where the sandy acid soils of the Piney Woods to the east or the thin limestone of the Hill Country to the west let many gardeners plant straight in the ground, growers here reach for raised beds, gypsum, and heavy organic amendment first. The season runs long — commonly 264 to 300 frost-free days across zones 8a to 9a — but it's the black clay, not the calendar, your beds have to answer to.
The 11 counties of Texas's Coastal Bend, anchored on Corpus Christi and the Nueces estuary, span USDA hardiness zones 9a to 10a with frost-free seasons running 311 to 343 days.