Harbor Island, South Carolina, sits in USDA hardiness zone 9b — a band that supports both cool-season staples and warm-season crops chosen to fit the local frost window.
On paper, okra, meyer lemon, california poppy, and artichoke all suit these conditions — on the ground, soil, sun, and drainage make the final call.
Even in Harbor Island, no two yards are alike.
A low spot, a south-facing slope, or a stand of trees moves the frost date and sun across a single Harbor Island lot. 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 Harbor Island — soil, climate, flood, and parcel records. How we handle your address.
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Harbor Island — the short answer
Harbor Island, South Carolina: USDA zone 9b, about 317 days between hard freezes, across 655 acres of town.
- USDA zone
- 9b
- USDA PHZM 2023
- Last hard freeze (28°F)
- Feb 3
- Beaufort County normal — NOAA 1991–2020, nearest to this town
- First hard freeze (28°F)
- Dec 17
- Beaufort County normal — NOAA 1991–2020, nearest to this town
- Days between freezes
- ~317
- Beaufort County normal — NOAA 1991–2020, nearest to this town
- Town area
- 655 acres
- US Census TIGER/Line 2025
Every figure names the dataset it came from. No 30-year normal resolves at this town’s own centroid, so the hard-freeze dates are Beaufort County’s — the closest measured record, labelled as such rather than passed off as local.
Hardiness Zone Range
Zone 9b is Harbor Island's average, not your lot's — a low corner or a tree line moves it. Against Harbor Island's 317-day season, see what your own ground reads.
Soil varies lot by lot — soil types explained.
What this means for growing in Harbor Island
Each reading below is measured for Harbor Island itself — here is what it means for a garden here, and the move an experienced grower makes about it.
Season length
From county recordsHarbor Island runs about 317 days between hard freezes (read from Beaufort County, the closest normal to Harbor Island) — close to year-round growing.
Frost is rarely the limit here; winter plantings are as real as summer ones, and the harder question is which crops shrug off the summer heat.
Grow cool-season crops through the mild winter, and choose heat-tolerant varieties for the summer beds.
NOAA 1991–2020 Climate Normals
Winter hardiness
MeasuredHarbor Island sits in USDA hardiness zone 9b.
The zone sets which perennials, shrubs, and fruit trees live through an average winter here — a plant rated for a colder zone is a safe bet, one rated warmer needs winter protection or gets treated as an annual.
Match perennials and fruit to the zone before you buy, so nothing you plant is a gamble against the cold.
USDA PHZM 2023
The kind of country Harbor Island is in
Harbor Island sits in the Southern Coastal Plain — EPA Level III, inside the wider Eastern Temperate Forests. That is read at Harbor Island's own centroid rather than borrowed from Beaufort County.
What Grows in Harbor Island
Every plant below cleared Harbor Island's own zone 9b and its 317-day season. Each card opens that plant's South Carolina profile. How we score.
Is it too late to plant in Harbor Island?
Too late for some crops, right on time for others — a growing season is a sequence, not a deadline. Cool-season crops can go in from around Jan 6; tender transplants wait until two to three weeks after the last 28°F hard freeze, which lands near Feb 3 (NOAA 1991–2020 climate normals); and from midsummer, planting counts back from the first fall freeze around Dec 17 — long-season crops need about 90 days of runway, quick greens only 30. And with a calendar this mild, the honest answer is that planting barely stops — winter opens seasons colder regions never see.
What's on the federal record near Harbor Island
Closest first, within ~10 miles of Harbor Island. Listing isn't leaking, and distance isn't exposure.
- HUNTING ISLAND STATE PARKUnderground Storage Tanks · 2.4 mi
- BFT- 432Nitrate · 2.9 mi
- EXPRESS LANE 5Underground Storage Tanks · 3.7 mi
- COUNTRY STOREUnderground Storage Tanks · 3.7 mi
- BFT- 446Nitrate · 3.9 mi
- BFT- 431Nitrate · 4.6 mi
- DOPSON SEAFOODUnderground Storage Tanks · 4.6 mi
- FOLLY RD GROCERYUnderground Storage Tanks · 5.5 mi
- FRIPP ISLAND PROPERTY OWNERS ASSOCIATIONUnderground Storage Tanks · 5.6 mi
- BFT- 487Nitrate · 5.6 mi
- FRIPP ISLAND MARINAUnderground Storage Tanks · 6.6 mi
- BFT-2149Nitrate · 6.7 mi
6 more sites are on the record inside the same radius. See them on the map
Measured from Harbor Island's center, not your beds. Run your own address for what's upwind of you specifically.
Environmental Intelligence
The counts behind that headline — every source type on the record near Harbor Island.
Sources Checked
within ~10 miles of Harbor Island
Severity Distribution
within ~10 miles of Harbor Island
Highest-Severity Sites
A note from Gnorman
What an experienced grower watches for around here
In and around Harbor Island, Nitrate runs higher than the national average — 24 sites within ~10 miles of Harbor Island. It's not cause for alarm — it's worth knowing, and there's a sensible way to grow around it.
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).
Check your specific parcel in Harbor Island
Get exact proximity distances to contamination sources for your specific parcel — plus soil, sun, drainage, and 1,086 plant recommendations.
25+ data sources read at your address, not the Harbor Island average
Your land is one point inside Harbor Island
Everything above resolves to Harbor Island as a whole — one PHZM band, read across 655 acres, with hard-freeze dates borrowed from Beaufort County’s record because no 30-year normal resolves at this town’s own centroid. Your parcel is one point inside that footprint. 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 town 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 local average.
Your Lot vs the Harbor Island Average
Harbor Island Average
- ●USDA Zones 9b, averaged across Harbor Island
- ●One soil character for all of Harbor Island
- ●Frost dates read at Harbor Island's scale: Feb 3 to Dec 17
YOUR Parcel
- ✓Your exact zone, not Harbor Island's 9b
- ✓Your SSURGO soil type & pH
- ✓Your sun exposure, cast in 3D
See MY Growing Report
Read your specific parcel in Harbor Island
Pull a site-specific report for your exact address in Harbor Island, South Carolina — soil, sun, drainage, frost risk, and scored plant recommendations.
Three things about your lot that Harbor Island averages can't show:
We read public map data around Harbor Island — soil, climate, flood, and parcel records. How we handle your address.
25+ data sources read at your address, not the Harbor Island average
How we know this about Harbor Island
The datasets: hardiness from the USDA ARS Plant Hardiness Zone Map 2023, read at this town’s own centroid; hard-freeze dates from NOAA 1991–2020 28°F normals at Beaufort County’s record, because none resolves here; boundaries and acreage from US Census TIGER/Line 2025; the contamination records from the federal sources named in their beats above. Soil is not read at town grain anywhere on this page — there is no town-resolution survey in our data, which is why you will find no soil grid here rather than a statewide one wearing a local label. The resolution ledger below names every figure this page inherited.
Common questions about Harbor Island
When does frost risk typically end in Harbor Island?
The last hard freeze (28°F) in Harbor Island typically lands around Feb 3, per NOAA 1991–2020 climate normals — earlier than the light-frost dates most charts quote. That marks the hard freeze, not the last light frost — lighter frosts keep biting past it, which is why tender transplants here wait until about Feb 24.
When is the first frost in Harbor Island?
The first hard freeze (28°F) in Harbor Island typically arrives around Dec 17, per NOAA 1991–2020 climate normals — the point tender summer crops finish. Lighter frosts run ahead of it, near Dec 3, so the watching starts about Nov 17 — about 317 days after the spring freeze cleared.
How long is the growing season in Harbor Island?
Measured between 28°F hard freezes, Harbor Island sees about 317 frost-free days — roughly Feb 3 through Dec 17, per NOAA 1991–2020 climate normals. Tender crops work a shorter one: nearer Feb 24 to Dec 3, about 282 days.
Is the soil safe to grow vegetables in Harbor Island?
The federal record around Harbor Island shows 50 documented sites, mostly Nitrate entries (24), the nearest Underground Storage Tanks record about 2.4 miles out — a typical footprint for a growing area, and proximity to a documented site is information, not a diagnosis of any one yard. It's worth seeing which recorded sites sit closest to where you grow, and testing the soil before new food beds near any of them.
How do I protect my plants from frost in Harbor Island?
From about Nov 17 the job here turns from planting to protecting — the last start even a 30-day crop can finish. As the season closes around the first 28°F hard freeze near Dec 17 (NOAA 1991–2020 climate normals), three moves buy time: row cover or an old sheet over tender plants on still, clear nights; water the soil the afternoon before a freeze, so it holds warmth overnight; and harvest tomatoes, peppers and basil before Dec 17. Hardy greens and roots shrug off light frost and sweeten after it — leave them in.
Everything above is measured at Harbor Island's scale — its 9b band and its 317-day season. Your yard writes its own version of Harbor Island's numbers: we read soil, sun, drainage and frost at your exact address. Try it for 14 days — no card required.
What this page reads at Harbor Island’s own scale
5 of the readings below were taken at Harbor Island's own scale — the 655 acres it covers and 50 documented sites around it; 5 are borrowed from a wider read, named and linked below.
Measured here
- Harbor Island's own USDA hardiness band, zones 9bUSDA PHZM 2023
- 50 documented contamination sites on the federal record near Harbor Island, the closest Underground Storage Tanks record about 2.4 miles out from the town centreFederal environmental registers
- Harbor Island's boundary and the 655 acres inside itUS Census TIGER/Line 2025
- Which of 1,086 plants clear zones 9b and a ~317-day seasonGrowable Ground crop-matching engine
- The ecoregion at Harbor Island's own centroid, the Southern Coastal PlainUS EPA Level III Ecoregions
Inherited from a wider read
- The 28°F hard-freeze dates — Harbor Island has no normal of its own, so its county's is the closest measured readfrom Beaufort County
- Soil character — no town-scale survey exists, so Harbor Island's 655 acres read through its county's SSURGO summaryfrom Beaufort County
- Growing-degree days and winter chill — measured county-wide only, so the county page carries themfrom Beaufort County
- The growing challenges every South Carolina grower plans around — written at state scale, so they stay on the state guidefrom South Carolina
- Butterfly and beetle records, and the farmland pesticide estimate — all published county-widefrom Beaufort County
What this page can’t tell you
- The soil pH, drainage, sun hours, and frost pockets on any one lot among Harbor Island's 655 acreswhy one lot differs from the next →
- Which side of Harbor Island you're on — a low spot frosts first and a south wall warms early, and one normal is being asked to speak for all 655 acresreading your own microclimate →
- How close that record sits to YOUR lot — the closest Underground Storage Tanks record about 2.4 miles out, measured from the town centrehow we read the record →
- Where cold air settles, which slopes face the sun, and which way the wind runs on your own ground — measured at your address, and averaged away by any Harbor Island-wide figureread your own land →