Plymouth, New Hampshire, sits in USDA hardiness zone 5b — a band that supports both cool-season staples and warm-season crops chosen to fit the local frost window.
Expect cabbage, cranberry, lavender, and collard greens to be strong candidates here; the deciding factors on any one parcel stay local — soil, sun, and drainage.
Even in Plymouth, no two yards are alike.
A low spot, a south-facing slope, or a stand of trees moves the frost date and sun across a single Plymouth lot. Enter your address and we'll score 1,086 plants against your land's actual soil, sun, and frost.
We read public map data around Plymouth — soil, climate, flood, and parcel records. How we handle your address.
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Plymouth — the short answer
Plymouth, New Hampshire: USDA zone 5b, about 157 days between hard freezes, across 4K acres of town.
- USDA zone
- 5b
- USDA PHZM 2023
- Last hard freeze (28°F)
- May 6
- NOAA 1991–2020 Climate Normals, 28°F — this town
- First hard freeze (28°F)
- Oct 10
- NOAA 1991–2020 Climate Normals, 28°F — this town
- Days between freezes
- ~157
- NOAA 1991–2020 Climate Normals, 28°F — this town
- Town area
- 4K acres
- US Census TIGER/Line 2025
Every figure names the dataset it came from. Hard-freeze dates are this town’s own 28°F normals: light frosts run a few weeks past them, and tender transplants usually wait 2–3 weeks after the last hard freeze.
Hardiness Zone Range
Zone 5b is Plymouth's average, not your lot's — a low corner or a tree line moves it. Against Plymouth's 157-day season, see what your own ground reads.
Soil varies lot by lot — soil types explained.
What this means for growing in Plymouth
Each reading below is measured for Plymouth itself — here is what it means for a garden here, and the move an experienced grower makes about it.
Season length
MeasuredPlymouth runs about 157 days between hard freezes — a moderate growing season.
There is room for the full run of cool-season crops plus a warm-season main crop, but the calendar is tight enough that a late spring or early fall frost still decides how much finishes.
Time warm-season transplants to your last hard freeze, and a few weeks of season extension turns a near-miss harvest into a sure one.
NOAA 1991–2020 Climate Normals
Winter hardiness
MeasuredPlymouth sits in USDA hardiness zone 5b.
The zone sets which perennials, shrubs, and fruit trees live through an average winter here — a plant rated for a colder zone is a safe bet, one rated warmer needs winter protection or gets treated as an annual.
Match perennials and fruit to the zone before you buy, so nothing you plant is a gamble against the cold.
USDA PHZM 2023
The kind of country Plymouth is in
Plymouth sits in the Northeastern Highlands — EPA Level III, inside the wider Northern Forests. That is read at Plymouth's own centroid rather than borrowed from Grafton County.
What Grows in Plymouth
Every plant below cleared Plymouth's own zone 5b and its 157-day season. Each card opens that plant's New Hampshire profile. How we score.
Is it too late to plant in Plymouth?
For most of the year, no — what changes is which crops still fit the days remaining. Cool-season crops can go in from around Apr 8; tender transplants wait until two to three weeks after the last 28°F hard freeze, which lands near May 6 (NOAA 1991–2020 climate normals); and from midsummer, planting counts back from the first fall freeze around Oct 10 — long-season crops need about 90 days of runway, quick greens only 30. Even past midsummer there is room for a true fall garden here, and garlic planted near the close carries the momentum into next year.
Documented around Plymouth
Survey cells within 31 miles of Plymouth checked for spotted lanternfly, none carrying a detection — a surveyed negative, not an absence of looking. Nearest documented record 34 miles off. What to watch for.
What's on the federal record near Plymouth
Closest first, within ~10 miles of Plymouth. Listing isn't leaking, and distance isn't exposure.
- PLYMOUTH VLG WATER AND SEWERPFAS · 0 ft
- DENNIS C DEARBORNUnderground Storage Tanks · 1.2 mi
- BELL ATLANTICUnderground Storage Tanks · 1.3 mi
- FORMER MUNCES KONVENIENCE PLYMOUTHUnderground Storage Tanks · 1.3 mi
- BARTLETT MOTORSUnderground Storage Tanks · 1.3 mi
- SPEARE MEMORIAL HOSPITALBrownfields · 1.4 mi
- THE LUCKY DOGUnderground Storage Tanks · 1.4 mi
- DOMINIC A LUCENTEUnderground Storage Tanks · 1.4 mi
- TRUE COLORS PRINT & DESIGNBrownfields · 1.4 mi
- FORMER HALL PROPERTYUnderground Storage Tanks · 1.4 mi
- PLYMOUTH GENERAL DENTISTRYBrownfields · 1.4 mi
- NH-APW 3Nitrate · 1.5 mi
6 more sites are on the record inside the same radius. See them on the map
Measured from Plymouth's center, not your beds. Run your own address for what's upwind of you specifically.
Environmental Intelligence
The counts behind that headline — every source type on the record near Plymouth.
Total Sites
205
within ~10 miles of Plymouth
Risk Level
Elevated
Highest-severity
1 Superfund site (none NPL-listed)
Sources Checked
within ~10 miles of Plymouth
Severity Distribution
within ~10 miles of Plymouth
Highest-Severity Sites
Know Before You Grow
- •Underground tanks leak petroleum as they age — near a former filling station, test the soil.
- •Near a brownfield, raised beds of imported soil give your food clean ground.
- •On a private well, test for nitrates: above 10 mg/L the water needs treatment before irrigating.
Check your specific parcel in Plymouth
Get exact proximity distances to contamination sources for your specific parcel — plus soil, sun, drainage, and 1,086 plant recommendations.
25+ data sources read at your address, not the Plymouth average
Your land is one point inside Plymouth
Everything above resolves to Plymouth as a whole — one PHZM band and one 28°F frost record, read across 4K acres. Your parcel is one point inside that footprint. Slope, tree cover, a low spot that pools cold air, and what is in the soil are all resolved at the address, and none of them are visible at town scale. That is the honest boundary of this page, and the reason the next step is a reading of your own ground rather than a better local average.
Your Lot vs the Plymouth Average
Plymouth Average
- ●USDA Zones 5b, averaged across Plymouth
- ●One soil character for all of Plymouth
- ●Frost dates read at Plymouth's scale: May 6 to Oct 10
YOUR Parcel
- ✓Your exact zone, not Plymouth's 5b
- ✓Your SSURGO soil type & pH
- ✓Your sun exposure, cast in 3D
See MY Growing Report
Read your specific parcel in Plymouth
Pull a site-specific report for your exact address in Plymouth, New Hampshire — soil, sun, drainage, frost risk, and scored plant recommendations.
Three things about your lot that Plymouth averages can't show:
We read public map data around Plymouth — soil, climate, flood, and parcel records. How we handle your address.
25+ data sources read at your address, not the Plymouth average
How we know this about Plymouth
The datasets: hardiness from the USDA ARS Plant Hardiness Zone Map 2023, read at this town’s own centroid; hard-freeze dates from NOAA 1991–2020 28°F normals at Plymouth’s own record; boundaries and acreage from US Census TIGER/Line 2025; the contamination records from the federal sources named in their beats above. Soil is not read at town grain anywhere on this page — there is no town-resolution survey in our data, which is why you will find no soil grid here rather than a statewide one wearing a local label. The resolution ledger below names every figure this page inherited.
Common questions about Plymouth
When does frost risk typically end in Plymouth?
The last hard freeze (28°F) in Plymouth typically lands around May 6, per NOAA 1991–2020 climate normals — earlier than the light-frost dates most charts quote. That marks the hard freeze, not the last light frost — lighter frosts keep biting past it, which is why tender transplants here wait until about May 27.
When is the first frost in Plymouth?
The first hard freeze (28°F) in Plymouth typically arrives around Oct 10, per NOAA 1991–2020 climate normals — the point tender summer crops finish. Lighter frosts run ahead of it, near Sep 26, so the watching starts about Sep 10 — about 157 days after the spring freeze cleared.
How long is the growing season in Plymouth?
Measured between 28°F hard freezes, Plymouth sees about 157 frost-free days — roughly May 6 through Oct 10, per NOAA 1991–2020 climate normals. Tender crops work a shorter one: nearer May 27 to Sep 26, about 122 days.
Is the soil safe to grow vegetables in Plymouth?
The federal record around Plymouth is a meaningful one — 205 documented sites, mostly Underground Storage Tanks entries (106), the nearest PFAS record under a tenth of a mile out — so a soil test before new food beds is a sensible precaution here, not a reason to hold back from growing. Remember that proximity to a documented site is information, not a diagnosis of any one yard; the contamination map shows exactly what sits where.
How do I protect my plants from frost in Plymouth?
From about Sep 10 the job here turns from planting to protecting — the last start even a 30-day crop can finish. As the season closes around the first 28°F hard freeze near Oct 10 (NOAA 1991–2020 climate normals), three moves buy time: row cover or an old sheet over tender plants on still, clear nights; water the soil the afternoon before a freeze, so it holds warmth overnight; and harvest tomatoes, peppers and basil before Oct 10. Hardy greens and roots shrug off light frost and sweeten after it — leave them in.
Everything above is measured at Plymouth's scale — its 5b band and its 157-day season. Your yard writes its own version of Plymouth's numbers: we read soil, sun, drainage and frost at your exact address. Try it for 14 days — no card required.
What this page reads at Plymouth’s own scale
7 of the readings below were taken at Plymouth's own scale — its own ~157-day season between 28°F freezes, the 3,760 acres it covers and 205 documented sites around it; 4 are borrowed from a wider read, named and linked below.
Measured here
- Plymouth's own USDA hardiness band, zones 5bUSDA PHZM 2023
- Plymouth's own 28°F hard-freeze dates, about May 6 and Oct 10 and the ~157-day span between themNOAA 1991–2020 Climate Normals
- 205 documented contamination sites on the federal record near Plymouth, the closest PFAS record under a tenth of a mile out from the town centreFederal environmental registers
- Plymouth's boundary and the 3,760 acres inside itUS Census TIGER/Line 2025
- Which of 1,086 plants clear zones 5b and a ~157-day seasonGrowable Ground crop-matching engine
- The ecoregion at Plymouth's own centroid, the Northeastern HighlandsUS EPA Level III Ecoregions
- Lanternfly survey cells around Plymouth checked, none carrying a detectionlydemapr (De Bona & Helmus), 10 km survey lattice
Inherited from a wider read
- Soil character — no town-scale survey exists, so Plymouth's 3,760 acres read through its county's SSURGO summaryfrom Grafton County
- Growing-degree days and winter chill — measured county-wide only, so the county page carries themfrom Grafton County
- The growing challenges every New Hampshire grower plans around — written at state scale, so they stay on the state guidefrom New Hampshire
- Butterfly and beetle records, and the farmland pesticide estimate — all published county-widefrom Grafton County
What this page can’t tell you
- The soil pH, drainage, sun hours, and frost pockets on any one lot among Plymouth's 3,760 acreswhy one lot differs from the next →
- Which side of Plymouth you're on — a low spot frosts first and a south wall warms early, and one normal is being asked to speak for all 3,760 acresreading your own microclimate →
- How close that record sits to YOUR lot — the closest PFAS record under a tenth of a mile out, measured from the town centrehow we read the record →
- Where cold air settles, which slopes face the sun, and which way the wind runs on your own ground — measured at your address, and averaged away by any Plymouth-wide figureread your own land →
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