Generally — Most Areas
Persian ironwood (zones 5-8) suits most of Vermont (4a-6a) — zones 5-6 are in range, and the rest of the state is the exception.
Your yard isn't the whole zone.
Vermont spans zones 4a-6a, 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 persian ironwood against your parcel's actual hardiness, soil, and sun.
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Zone Comparison
Persian Ironwood Needs
- USDA Zones: 5-8
- Frost-Free Days: 160+
- Sun: Full Sun
- Mature size: 30 ft tall
- Drought tolerance: High
Vermont Has
- USDA Zones: 4a-6a
- Last Hard Freeze (28°F): Apr 27 - May 5
- First Hard Freeze (28°F): Oct 10 - Oct 17
- Annual Rainfall: 34-44 inches
- Common Soils: Glacial till, Clay, Silt loam
Plant Zone Range (zones 5-8)
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 Persian Ironwood in Vermont
The frost window
Across Vermont, the last spring hard freeze (28°F) clears between Apr 27 and May 5, and the first fall hard freeze lands between Oct 10 and Oct 17 (NOAA Regional Climate Centers ACIS, 1991-2020). Counting from the latest last freeze to the earliest first freeze, that's a 158-day window you can count on — up to 173 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
Vermont runs as cold as USDA zone 4, and no sourced winter-hardiness floor is on record for persian ironwood, so this page does not state whether it overwinters here — and gives no fall establishment date on the strength of a guess. Whether persian ironwood is a permanent planting or a replant-every-spring crop for you turns on your own zone within Vermont; check its hardiness range against that before treating it as long-lived ground.
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 persian ironwood survives winter in part of Vermont, not across all of it. Whether the season is long enough — and warm enough — is a different question.
Frost-free days
Persian Ironwood wants 160+ frost-free days; a typical Vermont site sees ~163 (NOAA Regional Climate Centers ACIS, 1991-2020). That leaves a tight window — use transplants and pick early-maturing cultivars.
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
Persian Ironwood likes near-neutral soil (pH 5.5-7). That's the common-ground band across Vermont's glacial till and clay — a soil test confirms it for your site. It will grow across that whole span, but it does best between pH 5.5 and 6.5 — worth knowing before you decide whether a Vermont soil test result is a problem or just a number. Drainage matters: this plant wants well (dry spells). If your Vermont site is heavier clay or sits in a low spot, raised beds or amendment with compost solve it.
Plant pH and drainage requirements from USDA PLANTS Database. Vermont soil profile from USDA NRCS SSURGO. Site-specific verification: a 30-minute soil test from your local Extension lab.
Persian Ironwood in Vermont — Quick Answer
- Verdict: Generally — Most Areas
- Plant Zones: 5-8 (USDA PLANTS Database)
- State Zones: 4a-6a (USDA ARS PHZM 2023)
- Growing Season: 28°F hard freezes about Apr 27 - May 5 to Oct 10 - Oct 17 (NOAA Regional Climate Centers ACIS, 1991-2020)
What Else to Consider for Persian Ironwood in Vermont
Zone compatibility tells you about winter cold survival — but Vermont growers also need to think about:
Short growing season (100-130 frost-free days)
Rocky soils throughout the Green Mountains
Heavy clay in the Champlain Valley
What to actually do about these — and the constraints that apply to every Vermont grower, not just persian ironwood — is covered on the Vermont growing guide.
Timing shifts within Vermont
Persian Ironwood needs about 160 days of frost-free season to complete its cycle. 9 of Vermont’s 14 counties give it that outright. The tightest that does is Bennington County at 160 frost-free days — 0 to spare. Below that line you are transplanting or extending the season, not direct-sowing.
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"). Persian Ironwood's 160-day requirement: USDA PLANTS / Growable Ground plant database (minimum frost-free days). A parcel report resolves your address's own frost dates.
Where in Vermont Fits Best
Even within Vermont's zones 4a-6a, county microclimates differ enough to change what thrives. These counties carry the closest zone match for persian ironwood (USDA PHZM 2023):
Pollinator + Wildlife Value
Persian Ironwood draws native bees (low value, Growable Ground Plant Database). Planting it near vegetable beds can lift fruit set on neighboring crops. Outdoors, persian ironwood can only work that bloom inside Vermont's frost window — roughly 163 days, opening after the last 28°F freeze (Apr 27 - May 5) and closing at the first (Oct 10 - Oct 17), per NOAA Regional Climate Centers ACIS, 1991-2020.
Vermont Cooperative Extension
For Vermont-specific cultivar recommendations, planting calendars, and pest pressure for persian ironwood, the canonical source is UVM Extension. Their fact sheets carry the local trial data we can't generalize across 50 states.
Is Persian Ironwood native to Vermont?
No — the USDA PLANTS Database lists Persian Ironwood as introduced rather than native in the Lower 48, so it is not part of Vermont's native flora. It grows here as a garden plant; pairing it with a few Vermont natives keeps local pollinators fed too.
Looking for plants that belong here? The Vermont 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 Persian Ironwood in Vermont
When can I plant Persian Ironwood in Vermont?
Vermont's last spring hard freeze (28°F) clears between Apr 27 and May 5, and the first fall hard freeze lands between Oct 10 and Oct 17 (NOAA Regional Climate Centers ACIS, 1991-2020). No sourced winter-hardiness floor is on record for Persian Ironwood, so this page does not state whether it overwinters in Vermont 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 Persian Ironwood grown in across Vermont?
Vermont spans USDA hardiness zones 4a-6a (USDA ARS PHZM 2023). Persian Ironwood carries a range of zones 5-8, so the overlap zones are where outdoor growing is most reliable.
How many frost-free days does a typical Vermont site have?
A typical Vermont site sees ~163 frost-free days per year (derived from NOAA Regional Climate Centers ACIS, 1991-2020). Persian Ironwood needs 160+ frost-free days, so check whether your local microclimate runs above or below the state average before settling on a planting date.
Is Persian Ironwood native to Vermont?
No — the USDA PLANTS Database lists Persian Ironwood as introduced rather than native in the Lower 48, so it is not part of Vermont's native flora. It grows here as a garden plant; pairing it with a few Vermont natives keeps local pollinators fed too.
How should I amend the soil for Persian Ironwood in Vermont?
Persian Ironwood prefers pH 5.5-7 and well (dry spells) drainage (Growable Ground Plant Database). That sits in the common-ground band across Vermont soils — a 30-minute soil test from a local Extension lab confirms it for your specific site.
Will Persian Ironwood actually grow on my specific land in Vermont?
State-level zone + climate data is a sketch. A Growable Ground parcel report scores persian 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 Vermont
State-level data is a sketch. Your Growable Ground report scores persian ironwood against your parcel's exact soil, sun, drainage, and frost data — not zone averages.
Three things about your lot that Vermont persian ironwood averages can't show:
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