Generally — Most Areas
butterfly weed (zones 4-10) suits most of New Hampshire (3b-6b) — zones 4-6 are in range, and the rest of the state is the exception.
Butterfly Weed in New Hampshire — the short answer
Butterfly Weed in New Hampshire: hardy in zones 4–10, full sun, against a state median of ~171 frost-free days.
- Plant zones
- 4-10
- Manual horticultural correction (source not retained); NC State Extension and Missouri Botanical Garden, with the remaining rows from other published sources or Growable Ground compilation
- New Hampshire zones
- 3b-6b
- USDA PHZM 2023
- Frost window
- Apr 22 - May 4 – Oct 10 - Oct 21
- NOAA RCC ACIS 1991-2020, 28°F
- Shortest county season
- 145 days
- NOAA Regional Climate Centers ACIS, 1991-2020, county 28°F killing freeze
Plant data: Growable Ground Plant Database, compiled from FAO ECOCROP, USDA PLANTS and university Extension sources — per-field provenance varies and is published with the dataset.
Your yard isn't the whole zone.
New Hampshire spans zones 3b-6b, 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 butterfly weed against your parcel's actual hardiness, soil, and sun.
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New Hampshire is not one climate
New Hampshire’s winter-low ladder runs across 10 counties, from zone 4.5 in Coos County to zone 6 in Strafford County. That is 15°F between the two counties’ average coldest night — the difference between butterfly weed overwintering in the ground and coming under cover.
The middle half of 10 counties runs 5–6 zones, with a median of 5.5 zones — a 1.5-zone span end to end.
Measured across 10 New Hampshire counties. USDA PHZM 2023, per county. Quartiles are order statistics — every figure shown is a value a real county recorded, not an interpolation. Your own site sits somewhere inside this range; a parcel report resolves where.
Where in New Hampshire Fits Best
Even within New Hampshire's zones 3b-6b, county microclimates differ enough to change what thrives. These counties carry the closest zone match for butterfly weed (USDA PHZM 2023):
Zone Comparison
Butterfly Weed Needs
- USDA Zones: 4-10
- Frost-Free Days: 120+
- Sun: Full Sun
- Mature size: 2 ft tall
- Picking window: ~45 days of harvest
- Drought tolerance: High
New Hampshire Has
- USDA Zones: 3b-6b
- Last Hard Freeze (28°F): Apr 22 - May 4
- First Hard Freeze (28°F): Oct 10 - Oct 21
- Annual Rainfall: 36-50 inches
- Common Soils: Glacial till, Sandy loam, Rocky loam
Plant Zone Range (zones 4-10)
Preferred Soil pH
Plant data: Growable Ground Plant Database, compiled from FAO ECOCROP, USDA PLANTS, and university Extension sources — per-field provenance varies and is published with the dataset. State data: USDA ARS PHZM 2023, NOAA Climate Normals, NRCS SSURGO.
When to Plant Butterfly Weed in New Hampshire
The frost window
Across New Hampshire, the last spring hard freeze (28°F) clears between Apr 22 and May 4, and the first fall hard freeze lands between Oct 10 and Oct 21 (NOAA Regional Climate Centers ACIS, 1991-2020). Counting from the latest last freeze to the earliest first freeze, that's a 159-day window you can count on — up to 182 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
New Hampshire runs as cold as USDA zone 3, and no sourced winter-hardiness floor is on record for butterfly weed, so this page does not state whether it overwinters here — and gives no fall establishment date on the strength of a guess. Whether butterfly weed is a permanent planting or a replant-every-spring crop for you turns on your own zone within New Hampshire; check its hardiness range against that before treating it as long-lived ground.
Frost window: NOAA Climate Normals 1991-2020. Plant timing fields: Growable Ground Plant Database — frost-free days from FAO ECOCROP, days to harvest from university Extension production guides, and growing-degree-day and chill-hour minimums that are compilation estimates rather than published figures. 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 butterfly weed survives winter in part of New Hampshire, not across all of it. Whether the season is long enough — and warm enough — is a different question.
Frost-free days
Butterfly Weed wants 120+ frost-free days; a typical New Hampshire site sees ~171 (NOAA Regional Climate Centers ACIS, 1991-2020). That leaves a workable window — start indoors to bank time.
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
Butterfly Weed tolerates a wide pH range (pH 4.5-7.5) — 3 units, acid ground through alkaline — so soil acidity is rarely what limits it in New Hampshire. A soil test is still worth having, but for what else it tells you about this site, not to clear this plant. It will grow across that whole span, but it does best between pH 5 and 7 — worth knowing before you decide whether a New Hampshire soil test result is a problem or just a number. 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.
Plant pH requirements: FAO ECOCROP and USDA PLANTS, with the remaining rows from other published sources or Growable Ground compilation. Drainage: FAO ECOCROP, with the remaining rows from other published sources or Growable Ground compilation. New Hampshire soil profile from USDA NRCS SSURGO. Site-specific verification: a 30-minute soil test from your local Extension lab.
What Else to Consider for Butterfly Weed in New Hampshire
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)
Rocky glacial soils throughout the state
Harsh winters with deep snow cover
What to actually do about these — and the constraints that apply to every New Hampshire grower, not just butterfly weed — is covered on the New Hampshire growing guide.
Timing shifts within New Hampshire
Butterfly Weed needs about 120 days of frost-free season to complete its cycle. Even Coos County — New Hampshire’s shortest season at 145 frost-free days — clears that by 25 days, so season length isn’t the constraint anywhere in New Hampshire. What varies is your own parcel.
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"). Butterfly Weed's 120-day requirement: USDA PLANTS / Growable Ground plant database (minimum frost-free days). A parcel report resolves your address's own frost dates.
Pollinator + Wildlife Value
Butterfly Weed draws honeybees, native bees, butterflies, and moths (high value, Growable Ground Plant Database). Planting it near vegetable beds can lift fruit set on neighboring crops. Outdoors, butterfly weed can only work that bloom inside New Hampshire's frost window — roughly 171 days, opening after the last 28°F freeze (Apr 22 - May 4) and closing at the first (Oct 10 - Oct 21), per NOAA Regional Climate Centers ACIS, 1991-2020.
New Hampshire Cooperative Extension
For New Hampshire-specific cultivar recommendations, planting calendars, and pest pressure for butterfly weed, the canonical source is UNH Cooperative Extension. Their fact sheets carry the local trial data we can't generalize across 50 states.
Is Butterfly Weed native to New Hampshire?
Yes — the USDA PLANTS Database (accessed 2026-07-01) documents Butterfly Weed 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 Butterfly Weed in New Hampshire
When can I plant Butterfly Weed in New Hampshire?
New Hampshire's last spring hard freeze (28°F) clears between Apr 22 and May 4, and the first fall hard freeze lands between Oct 10 and Oct 21 (NOAA Regional Climate Centers ACIS, 1991-2020). No sourced winter-hardiness floor is on record for Butterfly Weed, so this page does not state whether it overwinters in New Hampshire 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 Butterfly Weed grown in across New Hampshire?
New Hampshire spans USDA hardiness zones 3b-6b (USDA ARS PHZM 2023). Butterfly Weed carries a range of zones 4-10, 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 ~171 frost-free days per year (derived from NOAA Regional Climate Centers ACIS, 1991-2020). Butterfly Weed needs 120+ frost-free days, so check whether your local microclimate runs above or below the state average before settling on a planting date.
Is Butterfly Weed native to New Hampshire?
Yes — the USDA PLANTS Database (accessed 2026-07-01) documents Butterfly Weed as native to New Hampshire. Planting it supports the pollinators and wildlife that evolved alongside it.
How should I amend the soil for Butterfly Weed in New Hampshire?
Butterfly Weed tolerates pH 4.5-7.5 and well (dry spells) drainage (FAO ECOCROP). That is a 3-unit span, acid ground through alkaline, so pH is rarely what limits this plant on a New Hampshire site — amend for drainage and organic matter first.
Will Butterfly Weed actually grow on my specific land in New Hampshire?
State-level zone + climate data is a sketch. A Growable Ground parcel report scores butterfly weed 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 butterfly weed against your parcel's exact soil, sun, drainage, and frost data — not zone averages.
Three things about your lot that New Hampshire butterfly weed averages can't show:
We read public map data around New Hampshire — soil, climate, flood, and parcel records. How we handle your address.
25+ data sources read at your address, not the New Hampshire butterfly weed average
Explore More
Growing guides for butterfly weed
Explore New Hampshire county by county
New Hampshire carries 10 counties with their own USDA zone — a sample of the growing pages for butterfly weed there:
Where else butterfly weed grows
Butterfly Weed's zone band crosses state lines — these are the states closest to New Hampshire in winter climate where it also has a page, plus the far ends of its range. Each one re-answers the question with that state's own record.
More to grow in New Hampshire
New Hampshire has a growing page for 806 plants — a rotating sample of the rest of the shelf.
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