The South County spans USDA hardiness zone 7a — a zone band wide enough that plant choice, not possibility, is the interesting question.
South County is the local name for Rhode Island's Washington County — the sandy, well-drained coastal plain along the state's southern shore. Ocean moderation holds it at USDA zone 7a with roughly 225 frost-free days (last frost around April 3, first around November 14), milder winters and a later fall than interior Rhode Island's zone 6b, where Kent and Providence counties run 210–221 frost-free days. That extra buffer favors longer-season warm crops, later succession plantings, and borderline-tender perennials the interior can't reliably carry. Expect tomato, garlic, red maple, and blueberry to be strong candidates here; the deciding factors on any one parcel stay local — soil, sun, and drainage.
The South County spans Rhode Island.
Your yard isn't all of the South County.
The South County spans USDA zones 7a, 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 South County — soil, climate, flood, and parcel records. How we handle your address.
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The South County — the short answer
The South County: USDA zones 7a, 225 frost-free days, in Rhode Island.
- USDA zones
- 7a
- USDA PHZM 2023, aggregated over the footprint
- Frost-free season
- 225 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 South County
Plants matched to the South County's USDA zones 7a, 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 South County
Plants the USDA PLANTS Database documents as native and present in this region’s state, kept only where the published hardiness range meets the South County’s USDA zones 7a — 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 South County
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 Inceptisols, at 76% of mapped acres, followed by Entisols (17%) and Histosols (7%). The most extensive named soils are Canton, Charlton, and Hinckley.
36% of those acres are well drained, and another 10% moderately well drained, 10% somewhat excessively drained. Topsoil pH runs 4.6–5.3 in that county’s own record. 16% of the footprint is classed prime farmland.
Soil order
Inceptisols
Drainage
Well drained
Topsoil pH
4.6–5.3
Hydric soils
23%
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 South County
The soil survey reads this ground county by county, and the readings above are those records summed across the South County. Here is what they mean for a garden here — and the move an experienced grower makes about each one.
Drainage
From county records36% of the mapped acres across the South County 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 South County runs pH 4.6–5.3 — acidic in the one record covering it.
Blueberries, potatoes, and rhododendrons thrive in it, but most vegetables start locking out nutrients below about pH 6.0 and grow pale and stunted no matter how much you feed them.
A measured lime application raises pH for the crops that need it — but test first, because the right rate depends on your own soil, not the county average.
USDA NRCS SSURGO
Wet ground
From county recordsAbout 23% of the ground across the South County is mapped as hydric — wetland — soil.
If your lot falls in one of those pockets, a standard in-ground bed will fight waterlogging all season, and roots that need air will struggle.
Check how your own ground drains before you dig; raised beds or moisture-loving plantings turn a wet corner from a problem into a niche.
USDA NRCS SSURGO
Safe to Grow Here?
What the federal record shows across the South County — and how to grow with it.
Across the South County's 1 county the federal record holds 1,484 documented sites, mostly Nitrate (650), Underground Storage Tanks (408) and Brownfields (341). The heaviest single county is Washington County, with 1,484.
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 South County to see which records sit where you actually grow.
Sources Checked
Summed across the county in the South County
A note from Gnorman
What an experienced grower watches for around here
In and around the South County, two things run higher than the national average across the county in the South County — Superfund (39 sites) and Nitrate (650 sites). It's not cause for alarm — it's worth knowing, and there's a sensible way to grow around it.
Superfund: Superfund sites represent the most severe contamination in the federal system.
Nitrate: Nitrate contamination primarily comes from agricultural fertilizer runoff and failing septic systems.
Commission professional soil testing before any food production (test for heavy metals, VOCs, and SVOCs).
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 South County
Everything above resolves to the South County as a whole — a footprint spanning USDA zones 7a. 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 South County Average
South County Average
- ●USDA Zones 7a, averaged across South County
- ●One soil character for all of South County
- ●State-average frost dates
YOUR Parcel
- ✓Your exact zone, not South County's 7a
- ✓Your SSURGO soil type & pH
- ✓Your sun exposure, cast in 3D
See MY Growing Report
Read your parcel in the South County
Pull a site-specific report for your exact address in the South County — soil, sun, drainage, frost risk, contamination, and scored plant recommendations.
Three things about your lot that South County averages can't show:
We read public map data around The South County — soil, climate, flood, and parcel records. How we handle your address.
25+ data sources read at your address, not the South County average
How we know this about the South County
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 South County
What hardiness zone is the South County?
The South County spans USDA hardiness zones 7a, 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 South County?
The South County's conditions suit plants such as Tomato, Garlic, Red Maple, Blueberry, Violet. 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 South County defined?
The South County 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 South County cover?
The South County spans Rhode Island. Each state's full growing guide is linked on this page.
What other growing regions cover the same states?
Block Island shares at least one state with the South County. 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 South County’s own scale
5 of the readings below were taken at the South County's own scale — the zone 7a band across its footprint and 1,484 documented federal contamination records across its one county, 1,484 of them in Washington County alone; one is borrowed from a wider read, named and linked below.
Measured here
- The USDA hardiness band 7a 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 — 1,484 documented federal contamination records across its one county, 1,484 of them in Washington County aloneEPA, USGS and USDA federal site records
- The soil order mix across the footprint — 76% Inceptisols, topsoil pH 4.6–5.3, 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 7afrom Rhode Island
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 →
