Grand Isle County, in Vermont, sits in USDA hardiness zone 5a — a band that supports both cool-season staples and warm-season crops chosen to fit the local frost window.
Growers here do well with cabbage, cranberry, lavender, and collard greens — with the usual caveat that any single yard's soil, sun, and drainage cast the deciding vote.
Grand Isle County lies within the Champlain Valley — a regional growing area with its own character.
Grounded in USDA PHZM 2023 · Growable Ground suitability scoring · NOAA 1991–2020 Climate Normals
Grand Isle County holds more than one microclimate.
Soils and elevations shift across Grand Isle 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 Grand Isle County — soil, climate, flood, and parcel records. How we handle your address.
No card required · your full report in seconds
Grand Isle County — the short answer
Grand Isle County, Vermont: USDA zone 5a, about 190 days between hard freezes, across 52K acres.
- USDA zone
- 5a
- USDA PHZM 2023
- Last hard freeze (28°F)
- Apr 20
- NOAA 1991–2020 Climate Normals, 28°F
- First hard freeze (28°F)
- Oct 27
- NOAA 1991–2020 Climate Normals, 28°F
- Days between freezes
- ~190
- NOAA 1991–2020 Climate Normals, 28°F
- County area
- 52K 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 5a is Grand Isle County's average, not your lot's — a low corner or a tree line moves it. Against Grand Isle County's 190-day season, see what your own ground reads.
Heat in Grand Isle County
Across a year, Grand Isle County accumulates about 2,303 growing degree days above 50°F, about 530 more than the middle Vermont county — ahead of every other Vermont county. 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 Grand Isle County
Across Grand Isle County, the ground is predominantly Inceptisols, where Covington, Benson, and Amenia are the most extensive named soil series. The soil is generally poorly drained with a silt loam surface. Topsoil pH runs about 6.5–6.7, neutral. Rainfall drains through hydrologic group D soils.
Soil order
Inceptisols
Drainage
Poorly drained
Prime farmland
23%
Hydric soils
41%
Soil still varies lot by lot — soil types explained.
How the ground varies across Grand Isle County
The USDA soil survey maps 27% of Grand Isle County as poorly drained — but another 65% drains differently: 22% somewhat excessively drained, 14% moderately well drained.
Covington is the most extensive named soil at 25% of mapped acres, then Benson (24%) and Amenia (13%).
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 Grand Isle County
Each reading below is measured for Grand Isle 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 Grand Isle County are poorly drained, in hydrologic group D — ground that sheds water slowly.
Beds can stay saturated for days after heavy rain, and the roots of most vegetables, berries, and fruit trees suffocate or rot in soil that never drains.
Raised beds or mounded rows lift roots above the wet zone; choose water-tolerant crops for the lowest spots.
USDA NRCS SSURGO
Surface pH
MeasuredTopsoil across Grand Isle County runs about pH 6.5–6.7, close to neutral.
This is the range most vegetables prefer — one correction you probably do not have to make, which is genuinely good news for a new bed.
Keep it there with compost rather than lime or sulfur, and only amend if your own soil test says otherwise.
USDA NRCS SSURGO
Season length
MeasuredGrand Isle County runs about 190 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
MeasuredGrand Isle County sits in USDA hardiness zone 5a.
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 Grand Isle County is in
Grand Isle County sits in the Eastern Great Lakes Lowlands — EPA Level III, inside the wider Eastern Temperate Forests. One consistent ecological setting across the whole county.
What Grows in Grand Isle County
We scored all 1,086 plants against Grand Isle County's own USDA zone 5a and its own 190-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 Vermont profile.
Is it too late to plant in Grand Isle County?
Too late for some crops, right on time for others — a growing season is a sequence, not a deadline. Cool-season crops can go in from around Mar 23; tender transplants wait until two to three weeks after the last 28°F hard freeze, which lands near Apr 20 (NOAA 1991–2020 climate normals); and from midsummer, planting counts back from the first fall freeze around Oct 27 — long-season crops need about 90 days of runway, quick greens only 30. Late in the year the fall bench takes over — quick greens, radishes, and garlic that repays you next summer.
Documented around Grand Isle County
Survey cells within 31 miles of Grand Isle County checked for spotted lanternfly, none carrying a detection — a surveyed negative, not an absence of looking. Nearest documented record 84 miles off. What to watch for.
- monarch butterfly124 documented records
Sighting records, so they follow observers as much as insects.
What gets applied to farmland in Grand Isle County
USGS estimates 1,518 lb of Glyphosate on Grand Isle County farmland in 2019, its largest by weight, ahead of Metolachlor & Metolachlor-s (1,498 lb) and Atrazine (1,198 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 Grand Isle County — and how to grow with it.
We checked the federal record across Grand Isle County — 77 documented sites across 2 of the 9 source types we track.
The most significant on record: 36 brownfield sites. Former commercial or industrial land where legacy contamination may persist.
The federal record across Grand Isle County is a modest one — a typical footprint for a growing area. Nothing here calls for alarm; it's worth knowing which recorded sites sit closest to where you grow, and each one on the map carries its type and location. If one turns out to be a near neighbor, a one-time soil test settles the question.
Sources: EPA, USGS — 1.8M documented sites tracked nationwide across 9 federal source types.
What's on the federal record near Grand Isle County
Closest first, across Grand Isle County. Listing isn't leaking, and distance isn't exposure.
- VTrans North Hero GarageUnderground Storage Tanks · 0.6 mi
- VTRANS-NORTH HEROBrownfields · 0.6 mi
- Alburg BridgeUnderground Storage Tanks · 0.7 mi
- Hero's WelcomeUnderground Storage Tanks · 1.1 mi
- HEROS WELCOMEBrownfields · 1.1 mi
- NORTH HERO TRANSFER STATIONBrownfields · 1.1 mi
- Knight FarmUnderground Storage Tanks · 2.0 mi
- BirdlandUnderground Storage Tanks · 2.0 mi
- North Hero HouseUnderground Storage Tanks · 2.0 mi
- Knight's StoreUnderground Storage Tanks · 2.0 mi
- Heise PropertyUnderground Storage Tanks · 2.0 mi
- VT DEPT OF FOREST PARKS AND REC BURTON ISLAND MAINTENANCEBrownfields · 2.1 mi
6 more sites are on the record inside the same radius. See them on the map
Measured from Grand Isle 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 Grand Isle County.
Severity Distribution
across Grand Isle County
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.
Check your specific parcel in Grand Isle 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 Grand Isle County average
Your land is one point inside Grand Isle County
Everything above resolves to Grand Isle County as a whole — one PHZM band and one county frost record, read across 52K 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 Grand Isle County Average
Grand Isle County Average
- ●USDA Zones 5a, averaged across Grand Isle County
- ●One soil character for all of Grand Isle County
- ●Frost dates read at Grand Isle County's scale: Apr 20 to Oct 27
YOUR Parcel
- ✓Your exact zone, not Grand Isle County's 5a
- ✓Your SSURGO soil type & pH
- ✓Your sun exposure, cast in 3D
See MY Growing Report
Read your parcel in Grand Isle County
Pull a site-specific report for your exact address in Grand Isle County, Vermont — soil, sun, drainage, frost risk, and scored plant recommendations.
Three things about your lot that Grand Isle County averages can't show:
We read public map data around Grand Isle County — soil, climate, flood, and parcel records. How we handle your address.
25+ data sources read at your address, not the Grand Isle County average
How we know this about Grand Isle 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 Grand Isle County carries no record of its own, the figure is inherited and labelled — the resolution ledger below names each.
Common questions about Grand Isle County
When does frost risk typically end in Grand Isle County?
The last hard freeze (28°F) in Grand Isle County typically lands around Apr 20, 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 11.
How long is the growing season in Grand Isle County?
Measured between 28°F hard freezes, Grand Isle County sees about 190 frost-free days — roughly Apr 20 through Oct 27, per NOAA 1991–2020 climate normals. Tender crops work a shorter one: nearer May 11 to Oct 13, about 155 days.
Is the soil safe to grow vegetables in Grand Isle County?
The federal record around Grand Isle County shows 77 documented sites, mostly Underground Storage Tanks entries (41), the nearest Underground Storage Tanks record about 0.6 miles out — a typical footprint for a growing area, and proximity to a documented site is information, not a diagnosis of any one yard. It's worth seeing which recorded sites sit closest to where you grow, and testing the soil before new food beds near any of them.
Everything above is measured at Grand Isle County's scale — its 5a band and its 190-day season. Your yard writes its own version of Grand Isle 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 Vermont's frost window, season length, and soil profile against the plant's real requirements.
What this page reads at Grand Isle County’s own scale
9 of the readings below were taken at Grand Isle County's own scale — its own ~190-day span between 28°F freezes, the 3 most extensive soil series mapped here and 77 documented sites inside its boundary; one is borrowed from a wider read, named and linked below.
Measured here
- Grand Isle County's own USDA hardiness band, zones 5aUSDA PHZM 2023
- Grand Isle County's own 28°F hard-freeze dates and its ~190-day span between themNOAA 1991–2020 Climate Normals
- The soil order, drainage, surface pH, and the 3 most extensive named soil series mapped in Grand Isle CountyUSDA NRCS SSURGO
- 77 documented contamination sites inside the county boundary, distance-sorted from its center — the closest Underground Storage Tanks record about 0.6 miles outFederal environmental registers
- Grand Isle County's boundary and the 52,334 acres inside itUS Census TIGER/Line 2025
- Which of 1,086 plants clear zones 5a and a ~190-day seasonGrowable Ground crop-matching engine
- Grand Isle County sitting wholly inside the Eastern Great Lakes LowlandsUS EPA Level III Ecoregions
- Open occurrence records documented in Grand Isle County for a tracked speciesGBIF derived datasets (CC0 / CC BY 4.0)
- Which agricultural compounds go onto Grand Isle County farmland, and roughly how muchUSGS NAWQA EPest county estimates
Inherited from a wider read
- The growing challenges every Vermont grower plans around — written at state scale, so they stay on the state guidefrom Vermont
What this page can’t tell you
- How the season shifts across Grand Isle County — the ~190 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 Grand Isle County's 52,334 acreswhy one lot differs from the next →
- Which of those 77 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 Grand Isle Countyread your own land →