Yankton County, in South Dakota, sits in USDA hardiness zone 5a — room for a real mix of vegetables, fruit, and perennials matched to the local frost calendar.
Well-matched crops include cabbage, cranberry, lavender, and collard greens, and the gap between "grows in the area" and "grows in your yard" is closed by soil, sun, and drainage.
Yankton County lies within the James River Valley — a regional growing area with its own character.
Grounded in USDA PHZM 2023 · Growable Ground suitability scoring · NOAA 1991–2020 Climate Normals
Yankton County holds more than one microclimate.
Soils and elevations shift across Yankton 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 Yankton County — soil, climate, flood, and parcel records. How we handle your address.
No card required · your full report in seconds
Yankton County — the short answer
Yankton County, South Dakota: USDA zone 5a, about 181 days between hard freezes, across 334K acres.
- USDA zone
- 5a
- USDA PHZM 2023
- Last hard freeze (28°F)
- Apr 18
- NOAA 1991–2020 Climate Normals, 28°F
- First hard freeze (28°F)
- Oct 16
- NOAA 1991–2020 Climate Normals, 28°F
- Days between freezes
- ~181
- NOAA 1991–2020 Climate Normals, 28°F
- County area
- 334K 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 Yankton County's average, not your lot's — a low corner or a tree line moves it. Against Yankton County's 181-day season, see what your own ground reads.
Heat in Yankton County
Across a year, Yankton County accumulates about 2,744 growing degree days above 50°F, about 318 more than the middle South Dakota county — ahead of 59 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 Yankton County
Across Yankton County, the ground is predominantly Mollisols, where Clarno, Ethan, and Egan are the most extensive named soil series. The soil is generally well drained with a loam surface. Topsoil pH runs about 6.7–7.5, neutral. Rainfall drains through hydrologic group B soils.
Soil order
Mollisols
Drainage
Well drained
Prime farmland
43%
Hydric soils
13%
Soil still varies lot by lot — soil types explained.
How the ground varies across Yankton County
The USDA soil survey maps 61% of Yankton County as well drained — but another 37% drains differently: 18% somewhat poorly drained, 10% poorly drained.
Clarno is the most extensive named soil at 23% of mapped acres, then Ethan (10%) and Egan (8%).
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 Yankton County
Each reading below is measured for Yankton 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 Yankton County are well drained, in hydrologic group B — 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 Yankton County runs about pH 6.7–7.5, 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
MeasuredYankton County runs about 181 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
MeasuredYankton 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 Yankton County is in
Yankton County spans 2 EPA Level III ecoregions — Northern Glaciated Plains (88%) and Western Corn Belt Plains (12%). Which one your land falls in changes what grows wild there and how the ground behaves, and a county-wide answer cannot tell you which.
What Grows in Yankton County
We scored all 1,086 plants against Yankton County's own USDA zone 5a and its own 181-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 Yankton 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 21; tender transplants wait until two to three weeks after the last 28°F hard freeze, which lands near Apr 18 (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.
Documented around Yankton County
- monarch butterfly20 documented records
Sighting records, so they follow observers as much as insects.
What gets applied to farmland in Yankton County
USGS estimates 160,691 lb of Glyphosate on Yankton County farmland in 2019, its largest by weight, ahead of Acetochlor (45,720 lb) and Metolachlor & Metolachlor-s (29,739 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 Yankton County — and how to grow with it.
We checked the federal record across Yankton County — 307 documented sites across 6 of the 9 source types we track.
The most significant on record: 3 Superfund sites (none NPL-listed). Sites tracked in EPA's Superfund program — from assessment-stage CERCLIS entries to confirmed National Priorities List cleanup sites.
There's a meaningful federal record across Yankton County — worth a look before you plant food, not a reason to hold back from growing. Proximity to a documented site is information, not a diagnosis of any one yard. A soil test before new food beds is the sensible precaution here, and the map shows exactly which sites sit where, so you can see what's actually near you.
Sources: EPA, USGS — 1.8M documented sites tracked nationwide across 9 federal source types.
What's on the federal record near Yankton County
Closest first, across Yankton County. Listing isn't leaking, and distance isn't exposure.
- 94N55W 5BABB2Nitrate · 1.1 mi
- ROAD KING INCBrownfields · 1.4 mi
- 95N55W32DDCDNitrate · 1.5 mi
- 95N56W36CCBC2Nitrate · 1.6 mi
- 94N56W 2DDDANitrate · 2.2 mi
- 94N55W10BBBB2Nitrate · 3.2 mi
- 95N55W 7CCCCNitrate · 3.3 mi
- 94N55W17ADCCNitrate · 3.5 mi
- 95N56W28AAAA2Nitrate · 3.7 mi
- 95N55W10CCCCNitrate · 4.3 mi
- 95N56W21AABBNitrate · 4.3 mi
- 95N55W 9BDCNitrate · 4.3 mi
6 more sites are on the record inside the same radius. See them on the map
Measured from Yankton 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 Yankton County.
Total Sites
307
across Yankton County
Risk Level
Elevated
Highest-severity
3 Superfund sites (none NPL-listed)
Sources Checked
across Yankton County
Severity Distribution
across Yankton County
Highest-Severity Sites
A note from Gnorman
What an experienced grower watches for around here
In and around Yankton County, Nitrate runs higher than the national average — 148 sites across Yankton 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 Yankton 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 Yankton County average
Your land is one point inside Yankton County
Everything above resolves to Yankton County as a whole — one PHZM band and one county frost record, read across 334K 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 Yankton County Average
Yankton County Average
- ●USDA Zones 5a, averaged across Yankton County
- ●One soil character for all of Yankton County
- ●Frost dates read at Yankton County's scale: Apr 18 to Oct 16
YOUR Parcel
- ✓Your exact zone, not Yankton County's 5a
- ✓Your SSURGO soil type & pH
- ✓Your sun exposure, cast in 3D
See MY Growing Report
Read your parcel in Yankton County
Pull a site-specific report for your exact address in Yankton County, South Dakota — soil, sun, drainage, frost risk, and scored plant recommendations.
Three things about your lot that Yankton County averages can't show:
We read public map data around Yankton County — soil, climate, flood, and parcel records. How we handle your address.
25+ data sources read at your address, not the Yankton County average
How we know this about Yankton 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 Yankton County carries no record of its own, the figure is inherited and labelled — the resolution ledger below names each.
Common questions about Yankton County
When does frost risk typically end in Yankton County?
The last hard freeze (28°F) in Yankton County typically lands around Apr 18, 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 9.
How long is the growing season in Yankton County?
Measured between 28°F hard freezes, Yankton County sees about 181 frost-free days — roughly Apr 18 through Oct 16, per NOAA 1991–2020 climate normals. Tender crops work a shorter one: nearer May 9 to Oct 2, about 146 days.
Is the soil safe to grow vegetables in Yankton County?
The federal record around Yankton County is a meaningful one — 307 documented sites, mostly Nitrate entries (148), the nearest Nitrate record about 1.1 miles out — so a soil test before new food beds is a sensible precaution here, not a reason to hold back from growing. Remember that proximity to a documented site is information, not a diagnosis of any one yard; the contamination map shows exactly what sits where.
Everything above is measured at Yankton County's scale — its 5a band and its 181-day season. Your yard writes its own version of Yankton 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 Yankton County’s own scale
9 of the readings below were taken at Yankton County's own scale — its own ~181-day span between 28°F freezes, the 3 most extensive soil series mapped here and 307 documented sites inside its boundary; one is borrowed from a wider read, named and linked below.
Measured here
- Yankton County's own USDA hardiness band, zones 5aUSDA PHZM 2023
- Yankton County's own 28°F hard-freeze dates and its ~181-day span between themNOAA 1991–2020 Climate Normals
- The soil order, drainage, surface pH, and the 3 most extensive named soil series mapped in Yankton CountyUSDA NRCS SSURGO
- 307 documented contamination sites inside the county boundary, distance-sorted from its center — the closest Nitrate record about 1.1 miles outFederal environmental registers
- Yankton County's boundary and the 333,561 acres inside itUS Census TIGER/Line 2025
- Which of 1,086 plants clear zones 5a and a ~181-day seasonGrowable Ground crop-matching engine
- The 2 ecoregions Yankton County spans, Northern Glaciated Plains the largestUS EPA Level III Ecoregions
- Open occurrence records documented in Yankton County for a tracked speciesGBIF derived datasets (CC0 / CC BY 4.0)
- Which agricultural compounds go onto Yankton 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 Yankton County — the ~181 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 Yankton County's 333,561 acreswhy one lot differs from the next →
- Which of those 307 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 Yankton Countyread your own land →