Mellette County, in South Dakota, sits in USDA hardiness zone 5a — a range where zone-matched perennials and frost-aware annual timing set what succeeds.
Expect cabbage, cranberry, lavender, and collard greens to be strong candidates here; the deciding factors on any one parcel stay local — soil, sun, and drainage.
Mellette County lies within the West River — a regional growing area with its own character.
Grounded in USDA PHZM 2023 · Growable Ground suitability scoring · NOAA 1991–2020 Climate Normals
Mellette County holds more than one microclimate.
Soils and elevations shift across Mellette 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 Mellette County — soil, climate, flood, and parcel records. How we handle your address.
No card required · your full report in seconds
Mellette County — the short answer
Mellette County, South Dakota: USDA zone 5a, about 170 days between hard freezes, across 837K acres.
- USDA zone
- 5a
- USDA PHZM 2023
- Last hard freeze (28°F)
- Apr 29
- NOAA 1991–2020 Climate Normals, 28°F
- First hard freeze (28°F)
- Oct 16
- NOAA 1991–2020 Climate Normals, 28°F
- Days between freezes
- ~170
- NOAA 1991–2020 Climate Normals, 28°F
- County area
- 837K 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 Mellette County's average, not your lot's — a low corner or a tree line moves it. Against Mellette County's 170-day season, see what your own ground reads.
Heat in Mellette County
Across a year, Mellette County accumulates about 2,680 growing degree days above 50°F, about 254 more than the middle South Dakota county — ahead of 54 of South Dakota’s 66 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 Mellette County
Across Mellette County, the ground is predominantly Entisols, where Lakoma, Okaton, and Imlay are the most extensive named soil series. The soil is generally well drained with a silty clay surface. Topsoil pH runs about 7.0–7.9, slightly alkaline. Rainfall drains through hydrologic group D soils.
Soil order
Entisols
Drainage
Well drained
Hydric soils
0%
Soil still varies lot by lot — soil types explained.
How the ground varies across Mellette County
The USDA soil survey maps 91% of Mellette County as well drained — but another 8% drains differently: 5% moderately well drained, 2% excessively drained.
Lakoma is the most extensive named soil at 12% of mapped acres, then Okaton (11%) and Imlay (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 Mellette County
Each reading below is measured for Mellette 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 Mellette County are well drained, in hydrologic group D — 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 Mellette County runs about pH 7.0–7.9, on the alkaline side.
Many vegetables cope, but acid-lovers like blueberries struggle, and iron and manganese lock up above about pH 7.5 — leaves yellow between the veins even in rich soil.
Elemental sulfur and generous organic matter lower pH slowly for the beds that need it; test first so you add only what the soil actually calls for.
USDA NRCS SSURGO
Season length
MeasuredMellette County runs about 170 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
MeasuredMellette 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 Mellette County is in
Mellette 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 Mellette County
We scored all 1,086 plants against Mellette County's own USDA zone 5a and its own 170-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 South Dakota profile.
Is it too late to plant in Mellette 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 1; tender transplants wait until two to three weeks after the last 28°F hard freeze, which lands near Apr 29 (NOAA 1991–2020 climate normals); and from midsummer, planting counts back from the first fall freeze around Oct 16 — long-season crops need about 90 days of runway, quick greens only 30. Even past midsummer there is room for a true fall garden here, and garlic planted near the close carries the momentum into next year.
What gets applied to farmland in Mellette County
USGS estimates 32,666 lb of Glyphosate on Mellette County farmland in 2019, its largest by weight, ahead of Metolachlor & Metolachlor-s (9,104 lb) and Metolachlor-s (7,790 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 Mellette County — and how to grow with it.
We checked the federal record across Mellette County — 140 documented sites across 3 of the 9 source types we track.
The most significant on record: 122 nitrate monitoring sites. Agricultural runoff and septic contamination — tracked at public water utilities (service-area exposure), private wells, and groundwater monitoring sites.
The federal record across Mellette 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 Mellette County
Closest first, across Mellette County. Listing isn't leaking, and distance isn't exposure.
- 42N29W34BDBDNitrate · 0.7 mi
- 42N29W34CAAC2Nitrate · 0.8 mi
- GILLEN'S STATIONUnderground Storage Tanks · 0.8 mi
- 42N29W34CAAC (2)Nitrate · 0.8 mi
- COUNTRY PRIDE COOPUnderground Storage Tanks · 0.9 mi
- GUS STOP IIUnderground Storage Tanks · 0.9 mi
- CITY OF WHITE RIVERUnderground Storage Tanks · 1.1 mi
- ROY & LEWIS FUERSTUnderground Storage Tanks · 1.1 mi
- TRIPLE C TRADING POSTUnderground Storage Tanks · 1.1 mi
- MELLETTE COUNTYUnderground Storage Tanks · 1.2 mi
- SD DEPT OF TRANSPORTATIONUnderground Storage Tanks · 1.4 mi
- 42N29W23CACCNitrate · 1.4 mi
6 more sites are on the record inside the same radius. See them on the map
Measured from Mellette 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 Mellette County.
Severity Distribution
across Mellette County
Highest-Severity Sites
A note from Gnorman
What an experienced grower watches for around here
In and around Mellette County, Nitrate runs higher than the national average — 122 sites across Mellette County. 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).
Check your specific parcel in Mellette 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 Mellette County average
Your land is one point inside Mellette County
Everything above resolves to Mellette County as a whole — one PHZM band and one county frost record, read across 837K 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 Mellette County Average
Mellette County Average
- ●USDA Zones 5a, averaged across Mellette County
- ●One soil character for all of Mellette County
- ●Frost dates read at Mellette County's scale: Apr 29 to Oct 16
YOUR Parcel
- ✓Your exact zone, not Mellette County's 5a
- ✓Your SSURGO soil type & pH
- ✓Your sun exposure, cast in 3D
See MY Growing Report
Read your parcel in Mellette County
Pull a site-specific report for your exact address in Mellette County, South Dakota — soil, sun, drainage, frost risk, and scored plant recommendations.
Three things about your lot that Mellette County averages can't show:
We read public map data around Mellette County — soil, climate, flood, and parcel records. How we handle your address.
25+ data sources read at your address, not the Mellette County average
How we know this about Mellette 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 Mellette County carries no record of its own, the figure is inherited and labelled — the resolution ledger below names each.
Common questions about Mellette County
When does frost risk typically end in Mellette County?
The last hard freeze (28°F) in Mellette County typically lands around Apr 29, 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 20.
How long is the growing season in Mellette County?
Measured between 28°F hard freezes, Mellette County sees about 170 frost-free days — roughly Apr 29 through Oct 16, per NOAA 1991–2020 climate normals. Tender crops work a shorter one: nearer May 20 to Oct 2, about 135 days.
Is the soil safe to grow vegetables in Mellette County?
The federal record around Mellette County shows 140 documented sites, mostly Nitrate entries (122), the nearest Nitrate record about 0.7 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 Mellette County's scale — its 5a band and its 170-day season. Your yard writes its own version of Mellette 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 South Dakota's frost window, season length, and soil profile against the plant's real requirements.
What this page reads at Mellette County’s own scale
8 of the readings below were taken at Mellette County's own scale — its own ~170-day span between 28°F freezes, the 3 most extensive soil series mapped here and 140 documented sites inside its boundary; one is borrowed from a wider read, named and linked below.
Measured here
- Mellette County's own USDA hardiness band, zones 5aUSDA PHZM 2023
- Mellette County's own 28°F hard-freeze dates and its ~170-day span between themNOAA 1991–2020 Climate Normals
- The soil order, drainage, surface pH, and the 3 most extensive named soil series mapped in Mellette CountyUSDA NRCS SSURGO
- 140 documented contamination sites inside the county boundary, distance-sorted from its center — the closest Nitrate record about 0.7 miles outFederal environmental registers
- Mellette County's boundary and the 836,678 acres inside itUS Census TIGER/Line 2025
- Which of 1,086 plants clear zones 5a and a ~170-day seasonGrowable Ground crop-matching engine
- Mellette County sitting wholly inside the Northwestern Great PlainsUS EPA Level III Ecoregions
- Which agricultural compounds go onto Mellette County farmland, and roughly how muchUSGS NAWQA EPest county estimates
Inherited from a wider read
- The growing challenges every South Dakota grower plans around — written at state scale, so they stay on the state guidefrom South Dakota
What this page can’t tell you
- How the season shifts across Mellette County — the ~170 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 Mellette County's 836,678 acreswhy one lot differs from the next →
- Which of those 140 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 Mellette Countyread your own land →