Coos County, in New Hampshire, sits in USDA hardiness zone 4b — a zone band wide enough that plant choice, not possibility, is the interesting question.
Reliable performers under these conditions include cabbage, cranberry, cilantro, and collard greens; what your own ground favors still comes down to its soil, sun, and drainage.
Coos County lies within the White Mountains — a regional growing area with its own character.
Grounded in USDA PHZM 2023 · Growable Ground suitability scoring · NOAA 1991–2020 Climate Normals
Coos County holds more than one microclimate.
Soils and elevations shift across Coos County, so your frost dates and drainage aren't the county average. 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 Coos County — soil, climate, flood, and parcel records. How we handle your address.
No card required · your full report in seconds
Coos County — the short answer
Coos County, New Hampshire: USDA zone 4b, about 145 days between hard freezes, across 1.1M acres.
- USDA zone
- 4b
- USDA PHZM 2023
- Last hard freeze (28°F)
- May 13
- NOAA 1991–2020 Climate Normals, 28°F
- First hard freeze (28°F)
- Oct 5
- NOAA 1991–2020 Climate Normals, 28°F
- Days between freezes
- ~145
- NOAA 1991–2020 Climate Normals, 28°F
- County area
- 1.1M acres
- US Census TIGER/Line 2025
Every figure names the dataset it came from. Hard-freeze dates are county 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 4b is Coos County's average, not your lot's — a low corner or a tree line moves it. Against Coos County's 145-day season, see what your own ground reads.
Heat in Coos County
Across a year, Coos County accumulates about 1,387 growing degree days above 50°F, about 643 fewer than the middle New Hampshire county — no other New Hampshire county banks fewer. Degree days are the heat a crop actually gets to work with — more of them is more room to ripen a long-season crop before the freeze closes the window.
Grounded in PRISM Climate Group, Oregon State University — 1991–2020 monthly normals
Soil in Coos County
Across Coos County, the ground is predominantly Spodosols, where Tunbridge, Peru, and Howland are the most extensive named soil series. The soil is generally well drained with a fine sandy loam surface. Topsoil pH runs about 4.6–5.2, very strongly acidic. Rainfall drains through hydrologic group C soils.
Soil order
Spodosols
Drainage
Well drained
Prime farmland
2%
Hydric soils
20%
Soil still varies lot by lot — soil types explained.
How the ground varies across Coos County
The USDA soil survey maps 49% of Coos County as well drained — but another 49% drains differently: 27% moderately well drained, 13% poorly drained.
Tunbridge is the most extensive named soil at 13% of mapped acres, then Peru (9%) and Howland (7%).
Which of them your own lot sits on is a parcel question, not a county one. Check your address for the survey at your boundary.
What this means for growing in Coos County
Each reading below is measured for Coos County itself — here is what it means for a garden here, and the move an experienced grower makes about it.
Drainage
MeasuredThe dominant soils across Coos County are well drained, in hydrologic group C — ground that drains quickly.
The upside is soil you can work early in spring and roots that never drown; the cost is that fast-draining ground dries out fast and leaches nutrients away before plants can use them.
Work in compost and mulch to hold moisture and feed, and water more often in short doses than deep and rarely.
USDA NRCS SSURGO
Surface pH
MeasuredTopsoil across Coos County runs about pH 4.6–5.2, on the acidic side.
Blueberries, potatoes, and rhododendrons thrive in it, but most vegetables start locking out nutrients below about pH 6.0 and grow pale and stunted no matter how much you feed them.
A measured lime application raises pH for the crops that need it — but test first, because the right rate depends on your own soil, not the county average.
USDA NRCS SSURGO
Wet ground
MeasuredAbout 20% of Coos County is mapped as hydric — wetland — soil.
If your lot falls in one of those pockets, a standard in-ground bed will fight waterlogging all season, and roots that need air will struggle.
Check how your own ground drains before you dig; raised beds or moisture-loving plantings turn a wet corner from a problem into a niche.
USDA NRCS SSURGO
Season length
MeasuredCoos County runs about 145 days between hard freezes — a short growing season.
Long-maturing crops like melons, sweet potatoes, and winter squash can run out of runway before the first hard freeze, ripening late or not at all.
Lead with fast-maturing varieties, and stretch the season on both ends with cold frames, low tunnels, or a greenhouse.
NOAA 1991–2020 Climate Normals
The kind of country Coos County is in
Coos County sits in the Northeastern Highlands — EPA Level III, inside the wider Northern Forests. One consistent ecological setting across the whole county.
What Grows in Coos County
We scored all 1,086 plants against Coos County's own USDA zone 4b and its own 145-day season between hard freezes, using the same matching engine that runs a full parcel report. These cleared both. Sun, soil pH and drainage vary lot by lot — those are the parcel questions below. Each card opens that plant's New Hampshire profile.
Is it too late to plant in Coos County?
Almost never — the real question is what to plant next. Cool-season crops can go in from around Apr 15; tender transplants wait until two to three weeks after the last 28°F hard freeze, which lands near May 13 (NOAA 1991–2020 climate normals); and from midsummer, planting counts back from the first fall freeze around Oct 5 — long-season crops need about 90 days of runway, quick greens only 30. Even here the calendar’s edges hold value: thirty-day greens late in the window, then garlic and a rested bed for spring.
Documented around Coos County
- Japanese beetle13 documented records
- monarch butterfly18 documented records
Sighting records, so they follow observers as much as insects.
What gets applied to farmland in Coos County
USGS estimates 1,342 lb of Glyphosate on Coos County farmland in 2019, its largest by weight, ahead of Atrazine (1,064 lb) and Metolachlor & Metolachlor-s (839 lb).
Farmland across the whole county, not any one lot. Check your address for the site-by-site record.
Safe to Grow Here?
What the federal record shows across Coos County — and how to grow with it.
We checked the federal record across Coos County — 590 documented sites across 8 of the 9 source types we track.
The most significant on record: 4 Superfund sites. Sites tracked in EPA's Superfund program — from assessment-stage CERCLIS entries to confirmed National Priorities List cleanup sites.
Coos County carries one of the heavier federal records we track — and that's not a verdict on your yard. Proximity to a documented site is information, not a diagnosis: nothing here says any particular parcel is affected. It does earn one concrete step — before food beds go in the ground, a professional soil test tells you exactly what you're working with, and raised beds with clean imported soil grow well almost anywhere in the meantime.
Sources: EPA, USGS — 1.8M documented sites tracked nationwide across 9 federal source types.
What's on the federal record near Coos County
Closest first, across Coos County. Listing isn't leaking, and distance isn't exposure.
- NH-DMW 15Nitrate · 2.4 mi
- NH-DMW 11Nitrate · 3.0 mi
- NH-DMW 22Nitrate · 3.2 mi
- NH-DMW 7Nitrate · 3.3 mi
- GALUSZKA FARMUnderground Storage Tanks · 3.3 mi
- FLINTS DAIRYUnderground Storage Tanks · 3.3 mi
- BEAUDOIN JOHN AUTOBrownfields · 3.3 mi
- NH-MNW 82Nitrate · 3.7 mi
- GORDS CORNER STORE FRM YESTERDAYSUnderground Storage Tanks · 4.0 mi
- TOWN OF DUMMERUnderground Storage Tanks · 4.3 mi
- NH-MNW 92Nitrate · 4.4 mi
- NH DOT PS 105Underground Storage Tanks · 4.6 mi
6 more sites are on the record inside the same radius. See them on the map
Measured from Coos County'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 Coos County.
Severity Distribution
across Coos County
Highest-Severity Sites
A note from Gnorman
What an experienced grower watches for around here
In and around Coos County, Nitrate runs higher than the national average — 228 sites across Coos County. Knowing it is half the work — and it's nothing a thoughtful grower can't plan for.
Nitrate: Nitrate contamination primarily comes from agricultural fertilizer runoff and failing septic systems.
Test well water for nitrate if you rely on a private well for irrigation (EPA standard: 10 mg/L).
Check your specific parcel in Coos County
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 Coos County average
Your land is one point inside Coos County
Everything above resolves to Coos County as a whole — one PHZM band and one county frost record, read across 1.1M 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 county 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 county average.
Your Lot vs the Coos County Average
Coos County Average
- ●USDA Zones 4b, averaged across Coos County
- ●One soil character for all of Coos County
- ●Frost dates read at Coos County's scale: May 13 to Oct 5
YOUR Parcel
- ✓Your exact zone, not Coos County's 4b
- ✓Your SSURGO soil type & pH
- ✓Your sun exposure, cast in 3D
See MY Growing Report
Read your parcel in Coos County
Pull a site-specific report for your exact address in Coos County, New Hampshire — soil, sun, drainage, frost risk, and scored plant recommendations.
Three things about your lot that Coos County averages can't show:
We read public map data around Coos County — soil, climate, flood, and parcel records. How we handle your address.
25+ data sources read at your address, not the Coos County average
How we know this about Coos County
The datasets: hardiness from the USDA ARS Plant Hardiness Zone Map 2023, read at county grain; hard-freeze dates from NOAA 1991–2020 28°F normals at this county’s own record where one resolves, and the labelled statewide window where none does; soils from the USDA NRCS SSURGO survey, area-weighted across the county’s own map units; boundaries and acreage from US Census TIGER/Line 2025; the contamination and pesticide records from the federal sources named in their beats above. Where Coos County carries no record of its own, the figure is inherited and labelled — the resolution ledger below names each.
Common questions about Coos County
When does frost risk typically end in Coos County?
The last hard freeze (28°F) in Coos County typically lands around May 13, 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 Jun 3.
How long is the growing season in Coos County?
Measured between 28°F hard freezes, Coos County sees about 145 frost-free days — roughly May 13 through Oct 5, per NOAA 1991–2020 climate normals. Tender crops work a shorter one: nearer Jun 3 to Sep 21, about 110 days.
Is the soil safe to grow vegetables in Coos County?
The federal record around Coos County runs heavier than most — 590 documented sites, mostly Underground Storage Tanks entries (261), the nearest Nitrate record about 2.4 miles out — so test the soil before planting food in the ground, and raised beds with clean imported soil grow well in the meantime. Even here, proximity to a documented site is information, not a diagnosis of any one yard; the contamination map shows exactly what's recorded and where.
How do gardeners stretch the season in Coos County?
With about 145 frost-free days between hard freezes, Coos County rewards the classic extension moves: floating row cover buys roughly two to four extra weeks at each shoulder — on this season that is a working window nearer 173 to 201 days — and cold frames or low tunnels buy more. Starting transplants indoors ahead of the May 13 hard-freeze normal stretches the season without touching the calendar.
Everything above is measured at Coos County's scale — its 4b band and its 145-day season. Your yard writes its own version of Coos County's numbers: we read soil, sun, drainage and frost at your exact address. Try it for 14 days — no card required.
Will It Grow Here?
Zone fit is the first question — each answer below reads New Hampshire's frost window, season length, and soil profile against the plant's real requirements.
What this page reads at Coos County’s own scale
9 of the readings below were taken at Coos County's own scale — its own ~145-day span between 28°F freezes, the 3 most extensive soil series mapped here and 590 documented sites inside its boundary; one is borrowed from a wider read, named and linked below.
Measured here
- Coos County's own USDA hardiness band, zones 4bUSDA PHZM 2023
- Coos County's own 28°F hard-freeze dates and its ~145-day span between themNOAA 1991–2020 Climate Normals
- The soil order, drainage, surface pH, and the 3 most extensive named soil series mapped in Coos CountyUSDA NRCS SSURGO
- 590 documented contamination sites inside the county boundary, distance-sorted from its center — the closest Nitrate record about 2.4 miles outFederal environmental registers
- Coos County's boundary and the 1,148,526 acres inside itUS Census TIGER/Line 2025
- Which of 1,086 plants clear zones 4b and a ~145-day seasonGrowable Ground crop-matching engine
- Coos County sitting wholly inside the Northeastern HighlandsUS EPA Level III Ecoregions
- Open occurrence records documented in Coos County for 2 tracked speciesGBIF derived datasets (CC0 / CC BY 4.0)
- Which agricultural compounds go onto Coos County farmland, and roughly how muchUSGS NAWQA EPest county estimates
Inherited from a wider read
- The growing challenges every New Hampshire grower plans around — written at state scale, so they stay on the state guidefrom New Hampshire
What this page can’t tell you
- How the season shifts across Coos County — the ~145 days above is one reading at its centre; the 12 towns below each carry their owntowns in this county →
- The soil pH, drainage, sun hours, and frost pockets on any one lot among Coos County's 1,148,526 acreswhy one lot differs from the next →
- Which of those 590 documented sites actually reaches your soil — that needs your address, the wind, and the groundwater directionhow we read the record →
- Where cold air settles, which slopes face the sun, and which way the wind runs on your own ground — none of it survives being averaged over Coos Countyread your own land →