The Turtle Mountains spans USDA hardiness zone 3b — room for a real mix of vegetables, fruit, and perennials matched to the local frost calendar.
The Turtle Mountains rise 300-400 feet above the surrounding drift prairie as a forested "island in a grassland sea" — an aspen-and-oak upland straddling the northern edges of Bottineau and Rolette counties that holds roughly 17% of North Dakota's native forest. That elevation, its lakes, and its cold-air pockets make it the coldest, shortest-season corner of the state: frost-free about 141 days at Bottineau and 145 at Rolette (both zone 3b), against a ~156-day North Dakota norm. Plan for a genuinely short, cool season here — it's the terrain, not the zone number, that sets this pocket apart from the rest of the northern border. Growers here do well with sunflower, potato, rhubarb, and american elm — with the usual caveat that any single yard's soil, sun, and drainage cast the deciding vote.
The Turtle Mountains spans North Dakota.
Your yard isn't all of the Turtle Mountains.
The Turtle Mountains spans USDA zones 3b, but your parcel sits in exactly one — and slope, tree cover, and low spots nudge it further. 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 Turtle Mountains — soil, climate, flood, and parcel records. How we handle your address.
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The Turtle Mountains — the short answer
The Turtle Mountains: USDA zones 3b, 141–145 frost-free days, in North Dakota.
- USDA zones
- 3b
- USDA PHZM 2023, aggregated over the footprint
- Frost-free season
- 141–145 days
- NOAA Regional Climate Centers ACIS, 1991-2020
- Counties
- 2
- US Census TIGER/Line 2025
- Region type
- County cluster
- Growable Ground growing-region registry
Region boundary: Growable Ground growing-region registry — curated county clusters, EPA Level III ecoregions, and town clusters drawn finer than any county. Where a region publishes no measured season, no season figure is shown.
Hardiness Zone Range
What Grows in the Turtle Mountains
Plants matched to the Turtle Mountains' USDA zones 3b, ordered by how much hardiness margin each has across the region — the ones with room to spare at both ends of this band lead. Each links to its full growing profile.
Native Plants of the Turtle Mountains
Plants the USDA PLANTS Database documents as native and present in this region’s state, kept only where the published hardiness range meets the Turtle Mountains’s USDA zones 3b — closest range match first. Presence is recorded by state, so a plant can be documented across the state and still be scarce in your corner of the region.
The ground across the Turtle Mountains
The USDA soil survey maps this ground county by county. These are those records weighted by land area across two member counties — this region’s own profile, not a state figure.
The ground is predominantly Mollisols, at 85% of mapped acres, followed by Alfisols (10%), Vertisols (3%) and Entisols (2%). Five soil orders appear somewhere inside the footprint, which is the honest reason a regional soil answer only goes so far. The most extensive named soils are Hamlet, Kelvin, and Souris.
48% of those acres are moderately well drained, and another 19% well drained, 16% somewhat poorly drained. Topsoil pH runs 6.7–7.5 between the lowest and the highest county on record. 37% of the footprint is classed prime farmland.
Soil order
Mollisols
Drainage
Moderately well drained
Topsoil pH
6.7–7.5
Hydric soils
17%
Soil changes across a driveway, so which of these your own ground sits on is a parcel question rather than a regional one. Bottineau County holds the most wetland ground here, at 18% — soil types explained.
USDA NRCS SSURGO via Soil Data Access
What this means for growing in the Turtle Mountains
The soil survey reads this ground county by county, and the readings above are those records summed across the Turtle Mountains. Here is what they mean for a garden here — and the move an experienced grower makes about each one.
Drainage
From county records48% of the mapped acres across the Turtle Mountains are moderately well drained — roughly the middle of the drainage range. That is area-weighted across all two of its mapped counties.
This is close to the middle most vegetables prefer: it holds enough water to carry a crop between rains without staying waterlogged. The catch is that a wet spring or a low corner can still tip it soggy.
Plant on the site as-is for most crops, but keep the lowest, slowest-draining beds for moisture-tolerant plantings.
USDA NRCS SSURGO
Surface pH
From county recordsTopsoil across the Turtle Mountains runs pH 6.7–7.5 — near neutral in all two of them.
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
Wet ground
From county recordsAbout 17% of the ground across the Turtle Mountains is mapped as hydric — wetland — soil. Bottineau County carries the most, at 18%.
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
Safe to Grow Here?
What the federal record shows across the Turtle Mountains — and how to grow with it.
Across the Turtle Mountains' 2 counties the federal record holds 514 documented sites, mostly Nitrate (402), Underground Storage Tanks (92) and Brownfields (15). The heaviest single county is Bottineau County, with 261.
That is a regional count, not a reading of any one lot — proximity to a documented site is information, not a diagnosis. Open the map outlined to the Turtle Mountains to see which records sit where you actually grow.
Sources Checked
Summed across the 2 counties in the Turtle Mountains
A note from Gnorman
What an experienced grower watches for around here
In and around the Turtle Mountains, Nitrate runs higher than the national average — 402 sites across the 2 counties in the Turtle Mountains. That's not a problem with your land — it's information about it.
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).
Sources: EPA, USGS — 1.8M documented sites tracked nationwide across 9 federal source types.
Your land is one point inside the Turtle Mountains
Everything above resolves to the Turtle Mountains as a whole — a footprint spanning USDA zones 3b. Your parcel sits in exactly one of them. 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 region 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 regional average.
Your Lot vs the Turtle Mountains Average
Turtle Mountains Average
- ●USDA Zones 3b, averaged across Turtle Mountains
- ●One soil character for all of Turtle Mountains
- ●State-average frost dates
YOUR Parcel
- ✓Your exact zone, not Turtle Mountains' 3b
- ✓Your SSURGO soil type & pH
- ✓Your sun exposure, cast in 3D
See MY Growing Report
Read your parcel in the Turtle Mountains
Pull a site-specific report for your exact address in the Turtle Mountains — soil, sun, drainage, frost risk, contamination, and scored plant recommendations.
Three things about your lot that Turtle Mountains averages can't show:
We read public map data around The Turtle Mountains — soil, climate, flood, and parcel records. How we handle your address.
25+ data sources read at your address, not the Turtle Mountains average
How we know this about the Turtle Mountains
The boundary: a cluster of neighboring counties. Growing regions have no official boundary, so this footprint is our published one, and every figure on this page was measured over the counties inside it rather than borrowed from the state around it.
The datasets: hardiness from the USDA ARS Plant Hardiness Zone Map 2023, aggregated across the footprint; the growing season from NOAA Regional Climate Centers ACIS 1991–2020 28°F normals, read at each member’s own record; boundaries from US Census TIGER/Line 2025; the contamination record from the federal sources named in that beat above; the soil from the USDA NRCS SSURGO survey, read at each member county’s own record and weighted to this footprint by land area. Where a member carries no record of its own, it is absent from the figure rather than filled in.
Common questions about the Turtle Mountains
What hardiness zone is the Turtle Mountains?
The Turtle Mountains spans USDA hardiness zones 3b, aggregated from the USDA Agricultural Research Service Plant Hardiness Zone Map 2023 across the region's counties. Zones reflect average annual extreme minimum temperatures from 1991–2020 data.
How long is the growing season in the Turtle Mountains?
Measured between 28°F hard freezes, the Turtle Mountains' counties mostly run 142 to 144 frost-free days, median 143 (NOAA Regional Climate Centers ACIS, 1991–2020, over 2 member counties). That 2-day spread is the honest read — no single season describes 2 counties, and each county guide below carries its own.
When does frost risk end in the Turtle Mountains?
Across the Turtle Mountains, the middle half of member counties see their last 28°F hard freeze between May 8 and May 9 (median May 9), and their first fall freeze between Sep 28 and Sep 29. Those are hard freezes, not the last light frost: tender transplants wait for about May 30, and elevation decides which end of a 1-day spread you garden in.
What grows well in the Turtle Mountains?
The Turtle Mountains' conditions suit plants such as Sunflower, Potato, Rhubarb, American Elm. What actually thrives on any one site still turns on its specific soil, sun, and drainage — we score each plant against the real conditions at your address.
How is the Turtle Mountains defined?
The Turtle Mountains is defined here as a curated cluster of 2 neighboring counties that share a growing character. Growing regions have no official boundary, so this footprint is our published one — every county in it is named on this page.
Which states does the Turtle Mountains cover?
The Turtle Mountains spans North Dakota. Each state's full growing guide is linked on this page.
What other growing regions cover the same states?
Red River Valley and The North Dakota Badlands share at least one state with the Turtle Mountains. Growing regions overlap and interlock — a single address can sit inside more than one, which is why the precise read is always the parcel, not the region.
What this page reads at the Turtle Mountains’s own scale
6 of the readings below were taken at the Turtle Mountains' own scale — the zone 3b band across its footprint, a median 143-day season across its 2 counties and 514 documented federal contamination records across its 2 counties, 261 of them in Bottineau County alone; one is borrowed from a wider read, named and linked below.
Measured here
- The USDA hardiness band 3b aggregated across all 2 counties in the footprintUSDA PHZM 2023
- The boundary itself — the 2 counties this region is curated fromGrowable Ground subregion registry
- The growing character that makes this region distinct from the states it crossesGrowable Ground subregion registry
- The 28°F season across the footprint — the middle half of its 2 counties run 142 to 144 frost-free days, median 143NOAA Regional Climate Centers ACIS, 1991-2020
- The federal contamination record over the whole footprint — 514 documented federal contamination records across its 2 counties, 261 of them in Bottineau County aloneEPA, USGS and USDA federal site records
- The soil order mix across the footprint — 85% Mollisols, topsoil pH 6.7–7.5, area-weighted across its 2 mapped countiesUSDA NRCS SSURGO
Inherited from a wider read
- The candidate plant list — its state's curated sets, merged and filtered to zones 3bfrom North Dakota
What this page can’t tell you
- Which end of the 2-day range your ground sits at — 142 days at one extreme, 144 at the other, decided mostly by elevationfrost dates explained →
- Which of those soils your own ground sits on — the survey maps them county-wide, and they change across a drivewaysoil types explained →
- The soil pH, drainage, sun hours, and frost pockets on one specific lotwhy one lot differs from the next →
Explore the Turtle Mountains
State growing guides
Counties in this region
Other growing regions across North Dakota
The flat floor of glacial Lake Agassiz along the Red River of the North — deep, dark lakebed clays and one of the coldest, shortest northern seasons on the platform (USDA zones 3b-4b) behind classic sugar-beet, potato, and spring-wheat country.
North Dakota's dry, wind-swept western half — the semi-arid side of the state's ~100th-meridian rainfall divide, where growers see roughly 6 to 8 inches less rain a year than the Red River Valley to the east. Zones run 4a-4b like much of the state, so the real work here isn't winter cold so much as drought: buttes-and-badlands terrain, hard prairie wind, and short-season dryland crops that need cover to hold moisture and finish before an early frost.