Hillsborough County, in New Hampshire, sits in USDA hardiness zone 6a — a band that supports both cool-season staples and warm-season crops chosen to fit the local frost window.
A short list that earns its place here — apple, sugar maple, blueberry, and potato — with any one site's soil, sun, and drainage making the final cut.
Grounded in USDA PHZM 2023 · Growable Ground suitability scoring · NOAA 1991–2020 Climate Normals
Hillsborough County holds more than one microclimate.
Soils and elevations shift across Hillsborough County, so your frost dates and drainage aren't the county average. Enter your address and we'll score 1,112 plants against your land's actual soil, sun, and frost.
We read public map data for this spot — soil, climate, flood, and parcel records. How we handle your address.
No card required · your full report in seconds
Quick Facts
USDA Zones
6a
Last Hard Freeze (28°F)
Apr 11
County normal — light frosts run a few weeks later
First Hard Freeze (28°F)
Nov 9
County normal — light frosts arrive a few weeks earlier
County Area
561K acres
Hardiness Zone Range
Zone maps are averages across Hillsborough County. Your yard's slope, trees, and frost pockets shift what actually grows — see your land's exact reading.
Soil in Hillsborough County
Across Hillsborough County, the ground is predominantly Spodosols, where Canton, Monadnock, and Marlow are the most extensive named soil series. The soil is generally well drained with a fine sandy loam surface. Topsoil pH runs about 4.3–5.0, very strongly acidic. Rainfall drains through hydrologic group B soils.
Soil order
Spodosols
Drainage
Well drained
Prime farmland
2%
Hydric soils
12%
Soil still varies lot by lot — soil types explained.
What Grows in Hillsborough County
Plants matched to Hillsborough County's USDA zones 6a — each links to its full growing profile.
Is it too late to plant in Hillsborough County?
Usually not — gardeners here simply switch what goes in the ground as the season moves. Cool-season crops can go in from around Mar 14; tender transplants wait until two to three weeks after the last 28°F hard freeze, which lands near Apr 11 (NOAA 1991–2020 climate normals); and from midsummer, planting counts back from the first fall freeze around Nov 9 — long-season crops need about 90 days of runway, quick greens only 30. Here the season winds down slowly: late sowings, a real autumn harvest, and garlic in the ground before the first hard freeze.
Growing Challenges in New Hampshire
What an experienced grower plans around here — each one has a move.
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.
For cultivar selection, pest pressure, and planting-time guidance specific to New Hampshire, the UNH Cooperative Extension is the authoritative local source.
Safe to Grow Here?
What the federal record shows across Hillsborough — and how to grow with it.
We checked the federal record across Hillsborough — 2,148 documented sites across 6 of the 9 source types we track.
The most significant on record: 35 Superfund sites. Sites tracked in EPA's Superfund program — from assessment-stage CERCLIS entries to confirmed National Priorities List cleanup sites.
Hillsborough 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.
Environmental Intelligence
Understanding what's nearby helps you make informed decisions about where and how to grow.
Sources Checked
across Hillsborough
Severity Distribution
across Hillsborough
Highest-Severity Sites
A note from Gnorman
What an experienced grower watches for around here
In and around Hillsborough County, two things run higher than the national average — Superfund (35 sites) and Toxic Release Inventory (134 sites). Knowing it is half the work — and it's nothing a thoughtful grower can't plan for.
Superfund: Superfund sites represent the most severe contamination in the federal system.
Toxic Release Inventory: TRI facilities report annual chemical releases to air, water, and land.
Commission professional soil testing before any food production (test for heavy metals, VOCs, and SVOCs).
Check prevailing wind direction — downwind parcels face higher exposure than upwind or crosswind locations.
Check your specific parcel in Hillsborough County
Get exact proximity distances to contamination sources for your specific parcel — plus soil, sun, drainage, and 1,112 plant recommendations.
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
Your Specific Parcel Matters
Hillsborough County Average
- ●USDA Zones 6a
- ●Generic soil type for the area
- ●State-average frost dates
YOUR Parcel
- ✓Your exact hardiness zone
- ✓Your SSURGO soil type & pH
- ✓Your sun exposure, cast in 3D
See MY Growing Report
Read your parcel in Hillsborough County
Pull a site-specific report for your exact address in Hillsborough County, New Hampshire — soil, sun, drainage, frost risk, and scored plant recommendations.
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
Key Growing Facts for Hillsborough County, New Hampshire
- USDA Hardiness Zones: 6a (USDA PHZM 2023)
- Last Hard Freeze (28°F): Apr 11 (county normal, NOAA 1991–2020 Climate Normals — light frosts can follow for a few weeks)
- First Hard Freeze (28°F): Nov 9 (county normal, NOAA 1991–2020 Climate Normals — light frosts can arrive a few weeks earlier)
- Days Between Hard Freezes: ~212 (county normal, NOAA 1991–2020 Climate Normals)
- County Land Area: 561K acres (US Census TIGER 2025)
Zone data: USDA ARS Plant Hardiness Zone Map 2023. Climate data: NOAA NCEI. County boundaries: US Census TIGER/Line 2025.
Frost dates here are the Hillsborough County average. Low spots and tree cover move them by days on any one yard — see your exact frost windows.
Frequently Asked Questions
What hardiness zone is Hillsborough County, New Hampshire?
Hillsborough County sits in USDA hardiness zone 6a, per the USDA Plant Hardiness Zone Map 2023. Zones reflect average annual extreme minimum temperatures from 1991–2020 weather data.
Is it too late to plant in Hillsborough County?
Usually not — gardeners here simply switch what goes in the ground as the season moves. Cool-season crops can go in from around Mar 14; tender transplants wait until two to three weeks after the last 28°F hard freeze, which lands near Apr 11 (NOAA 1991–2020 climate normals); and from midsummer, planting counts back from the first fall freeze around Nov 9 — long-season crops need about 90 days of runway, quick greens only 30. Here the season winds down slowly: late sowings, a real autumn harvest, and garlic in the ground before the first hard freeze.
When does frost risk typically end in Hillsborough County?
The last hard freeze (28°F) in Hillsborough County typically lands around Apr 11, per NOAA 1991–2020 climate normals — an earlier marker than the light-frost dates many planting charts quote. That marks the hard freeze, not the last light frost — light frosts can still bite for a few more weeks, so tender transplants usually wait another 2–3 weeks.
How long is the growing season in Hillsborough County?
Measured between 28°F hard freezes, Hillsborough County sees about 212 frost-free days — roughly Apr 11 through Nov 9, per NOAA 1991–2020 climate normals. Tender crops get a somewhat shorter practical window, since lighter frosts reach a few weeks past the hard-freeze dates on both ends.
What vegetables grow in Hillsborough County?
Hillsborough County's zone 6a supports a wide range — strong performers include Apple, Sugar Maple, Blueberry, Potato, and Lilac. What actually takes on any one site comes down to its soil, sun, and drainage, and we score each plant against the real conditions at your address.
Which hardiness zone is Hillsborough County, really?
Officially, Hillsborough County sits in USDA zone 6a (USDA PHZM 2023) — but a zone is a 30-year average of winter's coldest night across an area, and it can't see any one yard. A south-facing slope, a tree line, or a low frost pocket can shift a single site by half a zone either way, which is why neighboring gardeners often quote different numbers. We read the conditions at your exact address — soil, sun, slope, and frost — and score 1,112 plants against what's actually there.
Is the soil safe to grow vegetables in Hillsborough County?
The federal record around Hillsborough County runs heavier than most — 2,148 documented sites — 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.
Just moved to Hillsborough County — what should I know before planting?
Start with three facts. Hillsborough County sits in USDA zone 6a, which sets what survives winter; the last 28°F hard freeze typically clears around Apr 11, with about 212 frost-free days to work with (NOAA 1991–2020 climate normals); and 2,148 documented sites sit on the federal record here, so a soil test before food beds is the smart first step. From there, matching plants to your actual soil and sun is the fun part.
Everything on this page is a Hillsborough County average. Your yard writes its own version — 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.