The Sea Islands spans USDA hardiness zones 8b-9a — room for a real mix of vegetables, fruit, and perennials matched to the local frost calendar.
The barrier-island strip where Georgia and South Carolina meet the Atlantic — a two-state maritime band the mainland Lowcountry page doesn't reach. With ocean and tidal water on nearly every side, the frost-free season runs longer here than inland: a ~302-day median across the region's own coastal counties (vs ~290 for the mainland Lowcountry), stretching past 315 days on the sea islands around Beaufort and Charleston. The footprint is almost uniformly 9a — only inland-edge Colleton dips to 8b. Sandy island soils and salt air shaped a distinct growing tradition: Sea Island cotton, the extra-long-staple crop historically tied to these very islands, and the Gullah-Geechee garden of okra, benne, field peas, and sweet potato. Expect okra, tomato, collard greens, and sweet potato to be strong candidates here; the deciding factors on any one parcel stay local — soil, sun, and drainage.
The Sea Islands spans Georgia and South Carolina.
Your yard isn't all of the Sea Islands.
The Sea Islands spans USDA zones 8b-9a, 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 Sea Islands — soil, climate, flood, and parcel records. How we handle your address.
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The Sea Islands — the short answer
The Sea Islands: USDA zones 8b-9a, 290–320 frost-free days depending where in it you stand, across 2 states.
- USDA zones
- 8b-9a
- USDA PHZM 2023, aggregated over the footprint
- Shortest season here
- 290 days
- NOAA Regional Climate Centers ACIS, 1991-2020 — Liberty County
- Counties
- 10
- 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. The season figure is this region's own record, measured across its 10 member counties, not a state or national average.
Hardiness Zone Range
The Sea Islands is not one growing season
One answer for the Sea Islands averages 10 counties whose growing seasons are 30 days apart — from 290 frost-free days in Liberty County to 320 in Charleston 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 10 counties runs 299–304 days, with a median of 303 days — a 30-day span end to end.
Measured across 10 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.
Where the line runs inside the Sea Islands
The middle half of the Sea Islands runs 299–304 frost-free days, and 5 of its 10 counties sit outside that — 3 on the short side, 2 on the long. A regional planting date describes the middle well and the ends poorly, which is worth knowing before you follow one.
Under 299 frost-free days
3 counties
- Liberty County · 290 days
- Colleton County · 291 days
- Bryan County · 298 days
The end of the region that sets the planting calendar — start seed indoors here and the season stretches to meet the crop.
299–304 frost-free days
5 counties
0 of 5 shown
The middle half of the region, and the part a single regional season describes well.
Over 304 frost-free days
2 counties
- Charleston County · 320 days
- Beaufort County · 317 days
Long enough for a second succession of a quick crop after the first comes out.
Each county is placed by its OWN 28°F frost-free normal (NOAA Regional Climate Centers ACIS, 1991-2020), the same figure its own guide page publishes. Elevation, slope and cold-air drainage move a site within its county as well — which is the part only your address resolves.
What Grows in the Sea Islands
All 3 of the plants below that publish a season requirement clear even Liberty County’s 290 frost-free days — so on season alone, this grid works at both ends of the region. The 30-day spread still decides how far past this list you can push, and how early you can start.
Plants matched to the Sea Islands' USDA zones 8b-9a, 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 Sea Islands
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 Sea Islands’s USDA zones 8b-9a — 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 Sea Islands
The USDA soil survey maps this ground county by county. These are those records weighted by land area across ten member counties — this region’s own profile, not a state figure.
The ground is predominantly Ultisols, at 41% of mapped acres, followed by Entisols (30%), Spodosols (12%) and Alfisols (10%). Seven 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 Bohicket, Pelham, and Bladen.
33% of those acres are very poorly drained, and another 25% poorly drained, 16% somewhat poorly drained. Topsoil pH runs 4.6–7.3 between the lowest and the highest county on record. 4% of the footprint is classed prime farmland.
Soil order
Ultisols
Drainage
Very poorly drained
Topsoil pH
4.6–7.3
Hydric soils
64%
Soil changes across a driveway, so which of these your own ground sits on is a parcel question rather than a regional one. McIntosh County holds the most wetland ground here, at 77% — soil types explained.
USDA NRCS SSURGO via Soil Data Access
What this means for growing in the Sea Islands
The soil survey reads this ground county by county, and the readings above are those records summed across the Sea Islands. Here is what they mean for a garden here — and the move an experienced grower makes about each one.
Drainage
From county records33% of the mapped acres across the Sea Islands are very poorly drained — ground that sheds water slowly. That is area-weighted across all ten of its mapped counties.
Beds can stay saturated for days after heavy rain, and the roots of most vegetables, berries, and fruit trees suffocate or rot in soil that never drains.
Raised beds or mounded rows lift roots above the wet zone; choose water-tolerant crops for the lowest spots.
USDA NRCS SSURGO
Surface pH
From county recordsTopsoil across the Sea Islands runs pH 4.6–7.3 — acidic in nine of its ten counties.
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
Safe to Grow Here?
What the federal record shows across the Sea Islands — and how to grow with it.
Across the Sea Islands' 10 counties the federal record holds 5,960 documented sites, mostly Underground Storage Tanks (3,267), Nitrate (1,160) and Brownfields (1,155). The heaviest single county is Charleston County, with 1,778.
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 Sea Islands to see which records sit where you actually grow.
Sources Checked
Summed across the 10 counties in the Sea Islands
A note from Gnorman
What an experienced grower watches for around here
In and around the Sea Islands, Superfund runs higher than the national average — 91 sites across the 10 counties in the Sea Islands. That's not a problem with your land — it's information about it.
Superfund: Superfund sites represent the most severe contamination in the federal system.
Commission professional soil testing before any food production (test for heavy metals, VOCs, and SVOCs).
Sources: EPA, USGS — 1.8M documented sites tracked nationwide across 9 federal source types.
Your land is one point inside the Sea Islands
Everything above resolves to the Sea Islands as a whole — a footprint whose own counties record seasons 30 days apart, and hardiness across zones 8b-9a. 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 Sea Islands Average
Sea Islands Average
- ●USDA Zones 8b-9a, averaged across Sea Islands
- ●One soil character for all of Sea Islands
- ●State-average frost dates
YOUR Parcel
- ✓Your exact zone, not Sea Islands' 8b-9a
- ✓Your SSURGO soil type & pH
- ✓Your sun exposure, cast in 3D
See MY Growing Report
Read your parcel in the Sea Islands
Pull a site-specific report for your exact address in the Sea Islands — soil, sun, drainage, frost risk, contamination, and scored plant recommendations.
Three things about your lot that Sea Islands averages can't show:
We read public map data around The Sea Islands — soil, climate, flood, and parcel records. How we handle your address.
25+ data sources read at your address, not the Sea Islands average
How we know this about the Sea Islands
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 Sea Islands
What hardiness zone is the Sea Islands?
The Sea Islands spans USDA hardiness zones 8b-9a, 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 Sea Islands?
Measured between 28°F hard freezes, the Sea Islands' counties mostly run 299 to 304 frost-free days, median 303 (NOAA Regional Climate Centers ACIS, 1991–2020, over 10 member counties). That 5-day spread is the honest read — no single season describes 10 counties, and each county guide below carries its own.
When does frost risk end in the Sea Islands?
Across the Sea Islands, the middle half of member counties see their last 28°F hard freeze between Feb 9 and Feb 15 (median Feb 13), and their first fall freeze between Dec 8 and Dec 14. Those are hard freezes, not the last light frost: tender transplants wait for about Mar 6, and elevation decides which end of a 6-day spread you garden in.
What grows well in the Sea Islands?
The Sea Islands' conditions suit plants such as Okra, Tomato, Collard Greens, Sweet Potato, Fig, Peach. 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 Sea Islands defined?
The Sea Islands is defined here as a curated cluster of 10 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 Sea Islands cover?
The Sea Islands spans Georgia and South Carolina. Each state's full growing guide is linked on this page.
What other growing regions cover the same states?
Appalachia, Piedmont, Tidewater & Chesapeake, Blue Ridge, Vidalia / South Georgia, and Southwest Georgia / Dougherty Plain share at least one state with the Sea Islands. 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 Sea Islands’s own scale
6 of the readings below were taken at the Sea Islands' own scale — the zone 8b-9a band across its footprint, a median 303-day season across its 10 counties and 5,960 documented federal contamination records across its 10 counties, 1,778 of them in Charleston County alone; one is borrowed from a wider read, named and linked below.
Measured here
- The USDA hardiness band 8b-9a aggregated across all 10 counties in the footprintUSDA PHZM 2023
- The boundary itself — the 10 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 10 counties run 299 to 304 frost-free days, median 303NOAA Regional Climate Centers ACIS, 1991-2020
- The federal contamination record over the whole footprint — 5,960 documented federal contamination records across its 10 counties, 1,778 of them in Charleston County aloneEPA, USGS and USDA federal site records
- The soil order mix across the footprint — 41% Ultisols, topsoil pH 4.6–7.3, area-weighted across its 10 mapped countiesUSDA NRCS SSURGO
Inherited from a wider read
- The candidate plant list — all 2 member states' curated sets, merged and filtered to zones 8b-9afrom Georgia and South Carolina
What this page can’t tell you
- Which end of the 5-day range your ground sits at — 299 days at one extreme, 304 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 Sea Islands
State growing guides
Counties in this region
Other growing regions across Georgia and South Carolina
The vast eastern mountain region of steep hollows, thin acidic soils, and short upland seasons — apples, brambles, ramps, and forest crops on hard-won ground. (Union of the core Appalachian ecoregions.)
The rolling foothill belt between the Appalachians and the coastal plain, defined by heavy red clay soils that reward amendment and drainage. (Southern Piedmont; the Northern Piedmont is a separate ecoregion.)
The low, flat, tidal coastal plain around Chesapeake Bay — sandy soils, mild maritime winters, and a long season for vegetables and Southern staples.
The high, cool, forested spine of the southern Appalachians — layered ridges, acidic mountain loams, and a short upland season suited to apples and cold-hardy crops.
The federally designated Vidalia sweet-onion belt of Georgia's coastal plain — USDA zones 8b to 9a and a long frost-free season of roughly 290 days, from a median last frost near February 18 to a first frost around December 4.
Unlike Georgia's sandy east-central Vidalia belt or the state's mountains-to-coast average, this is the Dougherty Plain — a flat karst-limestone plain around Albany where near-surface limestone leaves soils near-neutral and center-pivots draw the Floridan aquifer (EPA Level IV ecoregion 65g). It is Georgia's row-crop heartland: peanuts, pecans, cotton, and corn on a long 8b–9a season of roughly 290–305 frost-free days. Growers here plan around limestone-derived soil chemistry and irrigation-fed summers rather than the acidic Coastal Plain sands that define most of the Southeast.