Oliver County, in North Dakota, sits in USDA hardiness zone 4a — a range where zone-matched perennials and frost-aware annual timing set what succeeds.
Growers here do well with cabbage, cranberry, turkish rocket, and collard greens — with the usual caveat that any single yard's soil, sun, and drainage cast the deciding vote.
Grounded in USDA PHZM 2023 · Growable Ground suitability scoring · NOAA 1991–2020 Climate Normals
Oliver County holds more than one microclimate.
Soils and elevations shift across Oliver 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 Oliver County — soil, climate, flood, and parcel records. How we handle your address.
No card required · your full report in seconds
Oliver County — the short answer
Oliver County, North Dakota: USDA zone 4a, about 154 days between hard freezes, across 462K acres.
- USDA zone
- 4a
- USDA PHZM 2023
- Last hard freeze (28°F)
- May 3
- NOAA 1991–2020 Climate Normals, 28°F
- First hard freeze (28°F)
- Oct 4
- NOAA 1991–2020 Climate Normals, 28°F
- Days between freezes
- ~154
- NOAA 1991–2020 Climate Normals, 28°F
- County area
- 462K 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 4a is Oliver County's average, not your lot's — a low corner or a tree line moves it. Against Oliver County's 154-day season, see what your own ground reads.
Heat in Oliver County
Across a year, Oliver County accumulates about 1,940 growing degree days above 50°F, about 27 more than the middle North Dakota county — ahead of 34 of North Dakota’s 53 counties. 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 Oliver County
Across Oliver County, the ground is predominantly Mollisols, where Williams, Werner, and Amor are the most extensive named soil series. The soil is generally well drained with a loam surface. Topsoil pH runs about 6.7–7.2, neutral. Rainfall drains through hydrologic group C soils.
Soil order
Mollisols
Drainage
Well drained
Prime farmland
9%
Hydric soils
3%
Soil still varies lot by lot — soil types explained.
How the ground varies across Oliver County
The USDA soil survey maps 86% of Oliver County as well drained — but another 13% drains differently: 5% moderately well drained, 3% excessively drained.
Williams is the most extensive named soil at 10% of mapped acres, then Werner (8%) and Amor (6%).
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 Oliver County
Each reading below is measured for Oliver 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 Oliver 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 Oliver County runs about pH 6.7–7.2, 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
MeasuredOliver County runs about 154 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
MeasuredOliver County sits in USDA hardiness zone 4a.
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 Oliver County is in
Oliver County sits in the Northwestern Great Plains — EPA Level III, inside the wider Great Plains. One consistent ecological setting across the whole county.
What Grows in Oliver County
We scored all 1,086 plants against Oliver County's own USDA zone 4a and its own 154-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 North Dakota profile.
Is it too late to plant in Oliver County?
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 5; tender transplants wait until two to three weeks after the last 28°F hard freeze, which lands near May 3 (NOAA 1991–2020 climate normals); and from midsummer, planting counts back from the first fall freeze around Oct 4 — long-season crops need about 90 days of runway, quick greens only 30. The tail of the season still works: sixty-day crops into late summer, quick greens after, garlic last of all.
Documented around Oliver County
- monarch butterfly1 documented records
Sighting records, so they follow observers as much as insects.
What gets applied to farmland in Oliver County
USGS estimates 106,267 lb of Glyphosate on Oliver County farmland in 2019, its largest by weight, ahead of Dicamba (12,351 lb) and 2,4-d (10,150 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 Oliver County — and how to grow with it.
We checked the federal record across Oliver County — 110 documented sites across 4 of the 9 source types we track.
The most significant on record: 3 Toxics Release Inventory facilities. Active industrial facilities reporting chemical releases to air, water, and land.
The federal record across Oliver 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 Oliver County
Closest first, across Oliver County. Listing isn't leaking, and distance isn't exposure.
- 142-084-15DANitrate · 1.4 mi
- Rays StandardUnderground Storage Tanks · 1.5 mi
- 142-084-14CBNitrate · 1.6 mi
- 142-084-14BCNitrate · 1.6 mi
- 142-084-08AABNitrate · 1.7 mi
- Corner StopUnderground Storage Tanks · 1.7 mi
- Corner Express of CenterUnderground Storage Tanks · 1.7 mi
- 142-084-08ABBNitrate · 1.8 mi
- North Dakota State Dept of TransportationUnderground Storage Tanks · 2.2 mi
- Oliver County ShopUnderground Storage Tanks · 2.4 mi
- 142-084-24BBA (Center well)Nitrate · 2.6 mi
- 143-084-28CCC2Nitrate · 3.6 mi
6 more sites are on the record inside the same radius. See them on the map
Measured from Oliver 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 Oliver County.
Total Sites
110
across Oliver County
Risk Level
Moderate
Highest-severity
3 Toxics Release Inventory facilities
Sources Checked
across Oliver County
Severity Distribution
across Oliver County
Highest-Severity Sites
A note from Gnorman
What an experienced grower watches for around here
In and around Oliver County, Nitrate runs higher than the national average — 92 sites across Oliver County. It's not cause for alarm — it's worth knowing, and there's a sensible way to grow around 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).
Check your specific parcel in Oliver 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 Oliver County average
Your land is one point inside Oliver County
Everything above resolves to Oliver County as a whole — one PHZM band and one county frost record, read across 462K 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 Oliver County Average
Oliver County Average
- ●USDA Zones 4a, averaged across Oliver County
- ●One soil character for all of Oliver County
- ●Frost dates read at Oliver County's scale: May 3 to Oct 4
YOUR Parcel
- ✓Your exact zone, not Oliver County's 4a
- ✓Your SSURGO soil type & pH
- ✓Your sun exposure, cast in 3D
See MY Growing Report
Read your parcel in Oliver County
Pull a site-specific report for your exact address in Oliver County, North Dakota — soil, sun, drainage, frost risk, and scored plant recommendations.
Three things about your lot that Oliver County averages can't show:
We read public map data around Oliver County — soil, climate, flood, and parcel records. How we handle your address.
25+ data sources read at your address, not the Oliver County average
How we know this about Oliver 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 Oliver County carries no record of its own, the figure is inherited and labelled — the resolution ledger below names each.
Common questions about Oliver County
When does frost risk typically end in Oliver County?
The last hard freeze (28°F) in Oliver County typically lands around May 3, 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 24.
How long is the growing season in Oliver County?
Measured between 28°F hard freezes, Oliver County sees about 154 frost-free days — roughly May 3 through Oct 4, per NOAA 1991–2020 climate normals. Tender crops work a shorter one: nearer May 24 to Sep 20, about 119 days.
Is the soil safe to grow vegetables in Oliver County?
The federal record around Oliver County shows 110 documented sites, mostly Nitrate entries (92), the nearest Nitrate record about 1.4 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 Oliver County's scale — its 4a band and its 154-day season. Your yard writes its own version of Oliver 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 North Dakota's frost window, season length, and soil profile against the plant's real requirements.
What this page reads at Oliver County’s own scale
9 of the readings below were taken at Oliver County's own scale — its own ~154-day span between 28°F freezes, the 3 most extensive soil series mapped here and 110 documented sites inside its boundary; one is borrowed from a wider read, named and linked below.
Measured here
- Oliver County's own USDA hardiness band, zones 4aUSDA PHZM 2023
- Oliver County's own 28°F hard-freeze dates and its ~154-day span between themNOAA 1991–2020 Climate Normals
- The soil order, drainage, surface pH, and the 3 most extensive named soil series mapped in Oliver CountyUSDA NRCS SSURGO
- 110 documented contamination sites inside the county boundary, distance-sorted from its center — the closest Nitrate record about 1.4 miles outFederal environmental registers
- Oliver County's boundary and the 462,338 acres inside itUS Census TIGER/Line 2025
- Which of 1,086 plants clear zones 4a and a ~154-day seasonGrowable Ground crop-matching engine
- Oliver County sitting wholly inside the Northwestern Great PlainsUS EPA Level III Ecoregions
- Open occurrence records documented in Oliver County for a tracked speciesGBIF derived datasets (CC0 / CC BY 4.0)
- Which agricultural compounds go onto Oliver County farmland, and roughly how muchUSGS NAWQA EPest county estimates
Inherited from a wider read
- The growing challenges every North Dakota grower plans around — written at state scale, so they stay on the state guidefrom North Dakota
What this page can’t tell you
- How the season shifts across Oliver County — the ~154 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 Oliver County's 462,338 acreswhy one lot differs from the next →
- Which of those 110 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 Oliver Countyread your own land →