Conditional — Some Areas
sourwood (zones 6-12) has limited zone overlap with New Hampshire (3b-6a). Only zones 6-6 in the state are suitable.
Your yard isn't the whole zone.
New Hampshire spans zones 3b-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 sourwood against your parcel's actual hardiness, soil, and sun.
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Zone Comparison
Sourwood Needs
- USDA Zones: 6-12
- Soil pH: 4 - 6.5
- Sun: Shade
- Frost-Free Days: 150+
New Hampshire Has
- USDA Zones: 3b-6a
- Last Frost: May 1 - Jun 1
- First Frost: Sep 10 - Oct 10
- Annual Rainfall: 36-50 inches
- Common Soils: Glacial till, Sandy loam, Rocky loam
Plant Zone Range (zones 6-12)
Preferred Soil pH
Plant data: USDA PLANTS Database / plant_species_v5.csv. State data: USDA ARS PHZM 2023, NOAA Climate Normals, NRCS SSURGO.
When to Plant Sourwood in New Hampshire
The frost window
Across New Hampshire, the last spring frost clears between May 1 and Jun 1, and the first fall frost lands between Sep 10 and Oct 10 (NOAA Climate Normals 1991-2020). Counting from the latest last frost to the earliest first frost, that's a 101-day window you can count on — up to 162 days on a mild site in a kind year.
Frost hardiness
Sourwood is cold-hardy to -13°F (USDA PLANTS Database), so you can plant on the early side of New Hampshire's window — even a few weeks before the final frost date.
Establishment timing
As a long-lived plant, sourwood isn't racing the calendar to a harvest date. Plant it in spring once the last-frost window passes so roots settle in through the full season, or in early fall while the soil still holds summer warmth.
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
Zone compatibility says you can survive winter here. Whether the growing season is long enough — and warm enough — is a different question.
Frost-free days
Sourwood wants 150+ frost-free days; a typical New Hampshire site sees ~170 (NOAA Climate Normals). That leaves a workable window — start indoors to bank time.
Chill hours
Sourwood requires ~600 chill hours (32-45°F dormancy window). New Hampshire typically banks ~1500 chill hours per winter (MSU Extension method), which keeps this plant on track.
Climate aggregates derive from USDA NRCS county-level hardiness data + Cornell CALS Extension GDD-by-region tables + MSU Extension chill-hours-by-zone (1991-2020 NOAA Climate Normals baseline).
Soil + Drainage Fit
Sourwood likes near-neutral soil (pH 4-6.5). That's the common-ground band across New Hampshire's glacial till and sandy loam — a soil test confirms it for your site.
Plant pH and drainage requirements from USDA PLANTS Database. New Hampshire soil profile from USDA NRCS SSURGO. Site-specific verification: a 30-minute soil test from your local Extension lab.
Sourwood in New Hampshire — Quick Answer
- Verdict: Conditional — Some Areas
- Plant Zones: 6-12 (USDA PLANTS Database)
- State Zones: 3b-6a (USDA ARS PHZM 2023)
- Growing Season: May 1 - Jun 1 to Sep 10 - Oct 10 (NOAA Climate Normals)
What Else to Consider
Zone compatibility tells you about winter cold survival — but New Hampshire growers also need to think about:
Very short season in the White Mountains (80-100 frost-free days)
In the mountains, fast varieties plus a cold frame or hoop house turn 90 days into a working season.
Rocky glacial soils throughout the state
Build up rather than dig out — a raised bed over cleared ground beats fighting granite for every planting hole.
Harsh winters with deep snow cover
Deep snow is a blanket, not a threat — plant to your true zone and the cover protects what the cold would test.
Pollinator + Wildlife Value
Sourwood draws pollinators (high value, USDA PLANTS Database). Planting it near vegetable beds can lift fruit set on neighboring crops.
New Hampshire Cooperative Extension
For New Hampshire-specific cultivar recommendations, planting calendars, and pest pressure for sourwood, the canonical source is UNH Cooperative Extension. Their fact sheets carry the local trial data we can't generalize across 50 states.
Is Sourwood native to New Hampshire?
Sourwood is native to parts of the Lower 48, but the USDA PLANTS Database (accessed 2026-07-01) does not document a native range in New Hampshire. It can still earn a place in a New Hampshire garden — the zone comparison above tells you whether it will thrive.
Looking for plants that belong here? The New Hampshire 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 Sourwood in New Hampshire
When can I plant Sourwood in New Hampshire?
New Hampshire's last spring frost clears between May 1 and Jun 1, and the first fall frost lands between Sep 10 and Oct 10 (NOAA Climate Normals 1991-2020). Sourwood is a long-lived planting, so target spring just after your local last frost — or early fall while the soil holds warmth — and let it establish through the season.
What hardiness zone is Sourwood grown in across New Hampshire?
New Hampshire spans USDA hardiness zones 3b-6a (USDA ARS PHZM 2023). Sourwood carries a range of zones 6-12, so the overlap zones are where outdoor growing is most reliable.
How many frost-free days does a typical New Hampshire site have?
A typical New Hampshire site sees ~170 frost-free days per year (derived from NOAA Climate Normals 1991-2020). Sourwood needs 150+ frost-free days, so check whether your local microclimate runs above or below the state average before settling on a planting date.
Is Sourwood native to New Hampshire?
Sourwood is native to parts of the Lower 48, but the USDA PLANTS Database (accessed 2026-07-01) does not document a native range in New Hampshire. It can still earn a place in a New Hampshire garden — the zone comparison above tells you whether it will thrive.
How should I amend the soil for Sourwood in New Hampshire?
Sourwood prefers pH 4-6.5 (USDA PLANTS Database). That sits in the common-ground band across New Hampshire soils — a 30-minute soil test from a local Extension lab confirms it for your specific site.
Will Sourwood actually grow on my specific land in New Hampshire?
State-level zone + climate data is a sketch. A Growable Ground parcel report scores sourwood 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 New Hampshire
State-level data is a sketch. Your Growable Ground report scores sourwood against your parcel's exact soil, sun, drainage, and frost data — not zone averages.
Three things about your exact spot that zone averages miss:
We read public map data for this spot — soil, climate, flood, and parcel records. How we handle your address.
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