Unlikely — Zone Mismatch
ironwood (zones 10-13) does not overlap with North Carolina's zone range (6a-9a). Growing outdoors is unlikely without significant protection.
2 zones short — what would close it
Ironwood is hardy to zone 10, and the warmest ground in North Carolina is zone 8 — 2 zones short. Planted in open ground it will not survive a North Carolina winter. To grow it here, grow ironwood under glass — a greenhouse is the only lift this wide the engine models.
A greenhouse is the lift this needs. How a greenhouse changes what you can grow →
Zone math from 10-13 (plant) against 6-8 (North Carolina). Lift modeled by crop_engine Sprint 20B effective_zone_modifier (+2 zones) via api/fast_sections.py Unlock Engine v2.
Your yard isn't the whole zone.
North Carolina spans zones 6a-9a, but your yard sits in exactly one — and slope, tree cover, and cold-air pockets nudge it further. Enter your address and we'll score ironwood against your parcel's actual hardiness, soil, and sun.
We read public map data for this spot — soil, climate, flood, and parcel records. How we handle your address.
No card required · your full report in seconds
Zone Comparison
Ironwood Needs
- USDA Zones: 10-13
- Frost-Free Days: 365+
- Sun: Full Sun
- Drought tolerance: High
North Carolina Has
- USDA Zones: 6a-9a
- Last Hard Freeze (28°F): Mar 11 - Mar 24
- First Hard Freeze (28°F): Nov 10 - Nov 25
- Annual Rainfall: 40-60 inches
- Common Soils: Red clay (Piedmont), Sandy loam (Coastal), Mountain loam
Plant Zone Range (zones 10-13)
Preferred Soil pH
Plant data: USDA PLANTS Database / Growable Ground plant catalog. State data: USDA ARS PHZM 2023, NOAA Climate Normals, NRCS SSURGO.
When to Plant Ironwood in North Carolina
The frost window
Across North Carolina, the last spring hard freeze (28°F) clears between Mar 11 and Mar 24, and the first fall hard freeze lands between Nov 10 and Nov 25 (NOAA Regional Climate Centers ACIS, 1991-2020). Counting from the latest last freeze to the earliest first freeze, that's a 231-day window you can count on — up to 259 days on a mild site in a kind year. That marks the hard freeze, not the last light frost, so tender transplants usually wait another 2-3 weeks.
Winter standing
North Carolina runs as cold as USDA zone 6, and no sourced winter-hardiness floor is on record for ironwood, so this page does not state whether it overwinters here — and gives no fall establishment date on the strength of a guess. Whether ironwood is a permanent planting or a replant-every-spring crop for you turns on your own zone within North Carolina; check its hardiness range against that before treating it as long-lived ground.
Timing tuned to sub-state frost dates — Swain County, not the statewide average.
Frost window: NOAA Climate Normals 1991-2020. Plant timing fields: USDA PLANTS Database. Your site's own frost dates can run earlier or later than the state range — a parcel report pins them down.
Growing Season Fit
The zone check says ironwood does not survive a North Carolina winter in the ground. The season figures below measure a different question — whether it could finish a season here at all — and they only bear on North Carolina under protection.
Frost-free days
Ironwood wants 365+ frost-free days; a typical North Carolina site sees ~245 (NOAA Regional Climate Centers ACIS, 1991-2020) — 120 days short of what it needs. A typical North Carolina season does not carry this crop to harvest outdoors, and a gap that size is not one an earlier sowing date or a faster cultivar closes; growing it here means growing it under cover.
GDD and chill-hour figures are computed from PRISM 1991-2020 monthly climate normals; frost-free days from NOAA Regional Climate Centers ACIS, 1991-2020. Each is the state median across its counties (P25/P75 span the within-state spread). Hardiness-zone range is USDA PHZM 2023.
Soil + Drainage Fit
Ironwood likes near-neutral soil (pH 6.8-8.6). That's the common-ground band across North Carolina's red clay (piedmont) and sandy loam (coastal) — a soil test confirms it for your site.
Your land, not the state average
North Carolina soil pH runs about 4.8–5.5, and that sits below ironwood's tolerated 6.8–8.6, so the typical North Carolina parcel needs lime before it will perform. SSURGO maps it swinging by full points parcel to parcel, so your map unit, not the state number, decides whether ironwood needs lime or sulfur.
Check your parcel → Source: USDA NRCS SSURGO.
Plant pH and drainage requirements from USDA PLANTS Database. North Carolina soil profile from USDA NRCS SSURGO. Site-specific verification: a 30-minute soil test from your local Extension lab.
Ironwood in North Carolina — Quick Answer
- Verdict: Unlikely — Zone Mismatch
- Plant Zones: 10-13 (USDA PLANTS Database)
- State Zones: 6a-9a (USDA ARS PHZM 2023)
- Growing Season: 28°F hard freezes about Mar 11 - Mar 24 to Nov 10 - Nov 25 (NOAA Regional Climate Centers ACIS, 1991-2020)
What Else to Consider for Ironwood in North Carolina
Zone compatibility tells you about winter cold survival — but North Carolina growers also need to think about:
Red Piedmont clay is hard to work and drains poorly
Humidity drives significant disease pressure
Hurricane risk on the coastal plain
Growing ironwood here specifically
Ironwood wants soil pH 6.8–8.6, but North Carolina's soils run acidic (SSURGO maps a dominant pH near 5.2) — below its range, nutrients lock up and growth stalls.
Test your soil and lime to raise pH into ironwood's 6.8–8.6 range before planting. How to handle it →
What to actually do about these — and the constraints that apply to every North Carolina grower, not just ironwood — is covered on the North Carolina growing guide.
Timing shifts within North Carolina
North Carolina isn't one climate. In Swain County, the last hard freeze (28°F) holds until about Apr 27 — roughly 41 days later than the recorded state median — so plant ironwood to your county's window, not the statewide date.
Ironwood needs about 365 days of frost-free season to complete its cycle. No North Carolina county gives it that outdoors: even Dare County, the state’s longest season at 303 frost-free days, falls 62 days short — so it needs transplants, a short-season variety, or covered growing.
Across North Carolina’s 100 counties the frost-free season runs from 178 days in Swain County to 303 days in Dare County — a spread of 125 days, which is why a single statewide planting date misleads. The median North Carolina county sees 245 frost-free days, which is 120 days short of what ironwood needs — so on a typical North Carolina parcel this is a transplant-or-protect crop, not a direct-sow one.
County last-freeze dates and frost-free day counts: NOAA Regional Climate Centers ACIS (1991-2020), county 28°F freeze (earlier than the folk 32°F "last frost"). Ironwood's 365-day requirement: USDA PLANTS / Growable Ground plant database (minimum frost-free days). A parcel report resolves your address's own frost dates.
North Carolina Cooperative Extension
For North Carolina-specific cultivar recommendations, planting calendars, and pest pressure for ironwood, the canonical source is NC State Extension. Their fact sheets carry the local trial data we can't generalize across 50 states.
Is Ironwood native to North Carolina?
Ironwood is native to parts of the Lower 48, but the USDA PLANTS Database (accessed 2026-07-01) does not document a native range in North Carolina. It can still earn a place in a North Carolina garden — the zone comparison above tells you whether it will thrive.
Looking for plants that belong here? The North Carolina growing guide lists USDA-documented natives for the state.
Native-range data: USDA PLANTS Database state-distribution records, accessed 2026-07-01.
Common Questions About Growing Ironwood in North Carolina
When can I plant Ironwood in North Carolina?
North Carolina's last spring hard freeze (28°F) clears between Mar 11 and Mar 24, and the first fall hard freeze lands between Nov 10 and Nov 25 (NOAA Regional Climate Centers ACIS, 1991-2020). No sourced winter-hardiness floor is on record for Ironwood, so this page does not state whether it overwinters in North Carolina and publishes no fall establishment date for it — check its hardiness range against your own zone before treating it as a permanent planting.
What hardiness zone is Ironwood grown in across North Carolina?
North Carolina spans USDA hardiness zones 6a-9a (USDA ARS PHZM 2023). Ironwood carries a range of zones 10-13, so the overlap zones are where outdoor growing is most reliable.
How many frost-free days does a typical North Carolina site have?
A typical North Carolina site sees ~245 frost-free days per year (derived from NOAA Regional Climate Centers ACIS, 1991-2020). Ironwood needs 365+ frost-free days, so check whether your local microclimate runs above or below the state average before settling on a planting date. In cooler counties like Swain, the freeze-free season runs shorter than the state average, so verify your own county's window.
Is Ironwood native to North Carolina?
Ironwood is native to parts of the Lower 48, but the USDA PLANTS Database (accessed 2026-07-01) does not document a native range in North Carolina. It can still earn a place in a North Carolina garden — the zone comparison above tells you whether it will thrive.
How should I amend the soil for Ironwood in North Carolina?
Ironwood prefers pH 6.8-8.6 (USDA PLANTS). That sits in the common-ground band across North Carolina soils — a 30-minute soil test from a local Extension lab confirms it for your specific site.
Will Ironwood actually grow on my specific land in North Carolina?
State-level zone + climate data is a sketch. A Growable Ground parcel report scores ironwood against your address's exact soil pH, drainage, sun, and frost-date data drawn from USDA SSURGO, NOAA, and PRISM — not state averages.
Check your specific parcel in North Carolina
State-level data is a sketch. Your Growable Ground report scores ironwood against your parcel's exact soil, sun, drainage, and frost data — not zone averages.
Three things about your lot that North Carolina ironwood averages can't show:
We read public map data around North Carolina — soil, climate, flood, and parcel records. How we handle your address.
25+ data sources read at your address, not the North Carolina ironwood average
Explore More
Growing guides for ironwood
Analysis by the Growable Ground research team, grounded in USDA PLANTS, USDA NRCS SSURGO, NOAA Climate Normals (1991-2020), and named Cooperative Extension sources. How we know →
Cite this dataset
Kirchick, M. (2026). Growable Ground Plant Database [Data set]. Zenodo. https://doi.org/10.5281/zenodo.21435643
Licensed CC BY-NC 4.0. DOI 10.5281/zenodo.21435643
Last updated: