Conditional — Some Areas
sunflower (zones 2-11) has limited zone overlap with New Hampshire (3b-6a). Only zones 3-6 in the state are suitable.
Your yard isn't the whole zone.
Sunflower is grown as an annual, so your winter zone isn't the deciding factor — your frost-free window is, and slope, trees, and low spots move the last-frost date across a single yard. Enter your address and we'll score sunflower against your parcel's actual frost dates, sun, and soil.
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Zone Comparison
Sunflower Needs
- USDA Zones: 2-11
- Soil pH: 5.5 - 8
- Sun: Full Sun
- Drainage: well (dry spells)
- Frost-Free Days: 70+
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 2-11)
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 Sunflower 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 tenderness
Sunflower is frost-tender — its listed minimum temperature is 41°F (USDA PLANTS Database) — so set plants out after the last frost has cleared your local site, not the state's earliest date.
Days to maturity vs. the window
At 80 days to maturity (USDA PLANTS Database), one crop fits New Hampshire's 101-day dependable window with 21 days of margin — plant at the front of the window to keep that cushion.
Timing tuned to sub-state frost dates — Coos 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
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
Sunflower wants 70+ frost-free days; a typical New Hampshire site sees ~170 (NOAA Climate Normals). That leaves comfortable headroom for succession planting.
Growing degree days
Sunflower needs ~1500 GDD (base 50°F) to ripen. The state median runs ~2900 GDD (USDA NRCS county aggregates), so New Hampshire's typical season clears that easily.
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
Sunflower likes near-neutral soil (pH 5.5-8). That's the common-ground band across New Hampshire's glacial till and sandy loam — a soil test confirms it for your site. Drainage matters: this plant wants well (dry spells). If your New Hampshire site is heavier clay or sits in a low spot, raised beds or amendment with compost solve it.
Your land, not the state average
New Hampshire's soils run mostly fine sandy loam, but SSURGO maps the series, texture, and drainage under your exact parcel — that map unit, not the state average, decides how sunflower performs.
Check your parcel → Source: USDA NRCS SSURGO.
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.
Sunflower in New Hampshire — Quick Answer
- Verdict: Conditional — Some Areas
- Plant Zones: 2-11 (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)
- Days to Maturity: 80 days
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.
Growing sunflower here specifically
Sunflower wants pH 5.5–8.0 and rates to USDA zones 2–11, but New Hampshire's soils are dominantly fine sandy loam — the fit is decided by your parcel's own map unit, not the state average.
Match sunflower to your parcel's SSURGO map unit — test pH and texture, and amend toward its 5.5–8.0 range. How to handle it →
Timing shifts within New Hampshire
New Hampshire isn't one climate. In Coos County, the last hard freeze (28°F) holds until about Apr 27 — roughly 11 days later than the recorded state median — so plant sunflower to your county's window, not the statewide date.
County last-freeze dates: NOAA/PRISM Climate Normals 1991-2020, 28°F threshold (earlier than the folk 32°F "last frost"). A parcel report resolves your address's own frost dates.
Pollinator + Wildlife Value
Sunflower draws pollinators (high value, USDA PLANTS Database). Planting it near vegetable beds can lift fruit set on neighboring crops.
Recommended Sunflower Varieties for New Hampshire
New Hampshire publishes no state variety trial for sunflower, so we won't invent a "best for New Hampshire" list. Choose types rated to your USDA hardiness zone (3b-6a), and confirm winter survival and drainage against your own parcel.
New Hampshire Cooperative Extension
For New Hampshire-specific cultivar recommendations, planting calendars, and pest pressure for sunflower, the canonical source is UNH Cooperative Extension. Their fact sheets carry the local trial data we can't generalize across 50 states.
Is Sunflower native to New Hampshire?
Yes — the USDA PLANTS Database (accessed 2026-07-01) documents Sunflower as native to New Hampshire. Planting it supports the pollinators and wildlife that evolved alongside it.
Native-range data: USDA PLANTS Database state-distribution records, accessed 2026-07-01.
Common Questions About Growing Sunflower in New Hampshire
When can I plant Sunflower 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). Sunflower is frost-tender — its listed minimum temperature is 41°F (USDA PLANTS Database) — so wait until the last frost has cleared your specific site before planting out.
Can Sunflower mature before first frost in New Hampshire?
Yes — Sunflower matures in 80 days (USDA PLANTS Database), and New Hampshire's dependable frost-free window runs 101 days (NOAA Climate Normals 1991-2020), leaving 21 days of margin. Plant just after last frost and it ripens ahead of the first fall frost.
What hardiness zone is Sunflower grown in across New Hampshire?
New Hampshire spans USDA hardiness zones 3b-6a (USDA ARS PHZM 2023). Sunflower carries a range of zones 2-11, 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). Sunflower needs 70+ 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 Coos, the freeze-free season runs shorter than the state average, so verify your own county's window.
Is Sunflower native to New Hampshire?
Yes — the USDA PLANTS Database (accessed 2026-07-01) documents Sunflower as native to New Hampshire. Planting it supports the pollinators and wildlife that evolved alongside it.
How should I amend the soil for Sunflower in New Hampshire?
Sunflower prefers pH 5.5-8 and well (dry spells) drainage (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 Sunflower actually grow on my specific land in New Hampshire?
State-level zone + climate data is a sketch. A Growable Ground parcel report scores sunflower 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 sunflower 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.
25+ data sources analyzed in seconds
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 →