Sullivan County, in Missouri, sits in USDA hardiness zone 6a — a band that supports both cool-season staples and warm-season crops chosen to fit the local frost window.
Reliable performers under these conditions include cabbage, hazelnut, lavender, and collard greens; what your own ground favors still comes down to its soil, sun, and drainage.
Sullivan County lies within the North Missouri Glaciated Plains (Green Hills) — a regional growing area with its own character.
Grounded in USDA PHZM 2023 · Growable Ground suitability scoring · NOAA 1991–2020 Climate Normals
Sullivan County holds more than one microclimate.
Soils and elevations shift across Sullivan 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 Sullivan County — soil, climate, flood, and parcel records. How we handle your address.
No card required · your full report in seconds
Sullivan County — the short answer
Sullivan County, Missouri: USDA zone 6a, about 208 days between hard freezes, across 415K acres.
- USDA zone
- 6a
- USDA PHZM 2023
- Last hard freeze (28°F)
- Apr 4
- NOAA 1991–2020 Climate Normals, 28°F
- First hard freeze (28°F)
- Oct 29
- NOAA 1991–2020 Climate Normals, 28°F
- Days between freezes
- ~208
- NOAA 1991–2020 Climate Normals, 28°F
- County area
- 415K 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 6a is Sullivan County's average, not your lot's — a low corner or a tree line moves it. Against Sullivan County's 208-day season, see what your own ground reads.
Heat in Sullivan County
Across a year, Sullivan County accumulates about 3,245 growing degree days above 50°F, about 508 fewer than the middle Missouri county — ahead of 7 of Missouri’s 115 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 Sullivan County
Across Sullivan County, the ground is predominantly Alfisols, where Gara, Armstrong, and Winnegan are the most extensive named soil series. The soil is generally well drained with a clay loam surface. Topsoil pH runs about 6.2–6.5, slightly acidic. Rainfall drains through hydrologic group D soils.
Soil order
Alfisols
Drainage
Well drained
Prime farmland
8%
Hydric soils
7%
Soil still varies lot by lot — soil types explained.
How the ground varies across Sullivan County
The USDA soil survey maps 40% of Sullivan County as well drained — but another 60% drains differently: 32% somewhat poorly drained, 20% moderately well drained.
Gara is the most extensive named soil at 28% of mapped acres, then Armstrong (24%) and Winnegan (14%).
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 Sullivan County
Each reading below is measured for Sullivan 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 Sullivan 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 Sullivan County runs about pH 6.2–6.5, 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
MeasuredSullivan County runs about 208 days between hard freezes — a long growing season.
There is slack for succession plantings and slow-finishing crops: many vegetables can be sown twice, and the heat-lovers have time to ripen fully.
Plan a second sowing of quick crops after the first comes out, and use the fall window most gardeners let sit idle.
NOAA 1991–2020 Climate Normals
Winter hardiness
MeasuredSullivan County sits in USDA hardiness zone 6a.
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 Sullivan County is in
Sullivan County sits in the Central Irregular Plains — EPA Level III, inside the wider Great Plains. One consistent ecological setting across the whole county.
What Grows in Sullivan County
We scored all 1,086 plants against Sullivan County's own USDA zone 6a and its own 208-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 Missouri profile.
Is it too late to plant in Sullivan 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 7; tender transplants wait until two to three weeks after the last 28°F hard freeze, which lands near Apr 4 (NOAA 1991–2020 climate normals); and from midsummer, planting counts back from the first fall freeze around Oct 29 — long-season crops need about 90 days of runway, quick greens only 30. Here the season winds down slowly: late sowings, a real autumn harvest, and garlic in the ground before the first hard freeze.
What gets applied to farmland in Sullivan County
USGS estimates 71,962 lb of Glyphosate on Sullivan County farmland in 2019, its largest by weight, ahead of Metolachlor & Metolachlor-s (26,798 lb) and Atrazine (18,224 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 Sullivan County — and how to grow with it.
We checked the federal record across Sullivan County — 64 documented sites across 5 of the 9 source types we track.
The most significant on record: 2 Toxics Release Inventory facilities. Active industrial facilities reporting chemical releases to air, water, and land.
The federal record across Sullivan 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 Sullivan County
Closest first, across Sullivan County. Listing isn't leaking, and distance isn't exposure.
- MILAN MAINT LOTUnderground Storage Tanks · 1500 ft
- MHTD & MSHPUnderground Storage Tanks · 1500 ft
- ARISHA ENTERPRISES INCUnderground Storage Tanks · 1800 ft
- H & Q USED CARSUnderground Storage Tanks · 0.5 mi
- MILAN PROCESSINGBrownfields · 0.6 mi
- MILAN PROCESSINGToxics Release Inventory · 0.6 mi
- CASEYS GENERAL STORE #3266Underground Storage Tanks · 0.6 mi
- T62N R20W 02CAA2Nitrate · 0.6 mi
- T62N R20W 02CAA1Nitrate · 0.7 mi
- DERYKE D-X SERVICEUnderground Storage Tanks · 0.7 mi
- T62N R20W 02CAC1Nitrate · 0.8 mi
- FARMLAND FOODS INCToxics Release Inventory · 0.9 mi
6 more sites are on the record inside the same radius. See them on the map
Measured from Sullivan 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 Sullivan County.
Total Sites
64
across Sullivan County
Risk Level
Moderate
Highest-severity
2 Toxics Release Inventory facilities
Sources Checked
across Sullivan County
Severity Distribution
across Sullivan County
Highest-Severity Sites
A note from Gnorman
What an experienced grower watches for around here
In and around Sullivan County, two things run higher than the national average across Sullivan County — CAFO (19 sites) and Nitrate (22 sites). It's not cause for alarm — it's worth knowing, and there's a sensible way to grow around it.
CAFO: CAFOs pose a different contamination profile than chemical sources.
Nitrate: Nitrate contamination primarily comes from agricultural fertilizer runoff and failing septic systems.
Wash all produce consumed raw thoroughly, especially leafy greens grown near CAFOs.
Test well water for nitrate if you rely on a private well for irrigation (EPA standard: 10 mg/L).
Check your specific parcel in Sullivan 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 Sullivan County average
Your land is one point inside Sullivan County
Everything above resolves to Sullivan County as a whole — one PHZM band and one county frost record, read across 415K 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 Sullivan County Average
Sullivan County Average
- ●USDA Zones 6a, averaged across Sullivan County
- ●One soil character for all of Sullivan County
- ●Frost dates read at Sullivan County's scale: Apr 4 to Oct 29
YOUR Parcel
- ✓Your exact zone, not Sullivan County's 6a
- ✓Your SSURGO soil type & pH
- ✓Your sun exposure, cast in 3D
See MY Growing Report
Read your parcel in Sullivan County
Pull a site-specific report for your exact address in Sullivan County, Missouri — soil, sun, drainage, frost risk, and scored plant recommendations.
Three things about your lot that Sullivan County averages can't show:
We read public map data around Sullivan County — soil, climate, flood, and parcel records. How we handle your address.
25+ data sources read at your address, not the Sullivan County average
How we know this about Sullivan 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 Sullivan County carries no record of its own, the figure is inherited and labelled — the resolution ledger below names each.
Common questions about Sullivan County
When does frost risk typically end in Sullivan County?
The last hard freeze (28°F) in Sullivan County typically lands around Apr 4, 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 Apr 25.
How long is the growing season in Sullivan County?
Measured between 28°F hard freezes, Sullivan County sees about 208 frost-free days — roughly Apr 4 through Oct 29, per NOAA 1991–2020 climate normals. Tender crops work a shorter one: nearer Apr 25 to Oct 15, about 173 days.
Is the soil safe to grow vegetables in Sullivan County?
The federal record around Sullivan County shows 64 documented sites, mostly Nitrate entries (22), the nearest Underground Storage Tanks record about 0.3 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 Sullivan County's scale — its 6a band and its 208-day season. Your yard writes its own version of Sullivan 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 Missouri's frost window, season length, and soil profile against the plant's real requirements.
What this page reads at Sullivan County’s own scale
8 of the readings below were taken at Sullivan County's own scale — its own ~208-day span between 28°F freezes, the 3 most extensive soil series mapped here and 64 documented sites inside its boundary; one is borrowed from a wider read, named and linked below.
Measured here
- Sullivan County's own USDA hardiness band, zones 6aUSDA PHZM 2023
- Sullivan County's own 28°F hard-freeze dates and its ~208-day span between themNOAA 1991–2020 Climate Normals
- The soil order, drainage, surface pH, and the 3 most extensive named soil series mapped in Sullivan CountyUSDA NRCS SSURGO
- 64 documented contamination sites inside the county boundary, distance-sorted from its center — the closest Underground Storage Tanks record about 0.3 miles outFederal environmental registers
- Sullivan County's boundary and the 414,708 acres inside itUS Census TIGER/Line 2025
- Which of 1,086 plants clear zones 6a and a ~208-day seasonGrowable Ground crop-matching engine
- Sullivan County sitting wholly inside the Central Irregular PlainsUS EPA Level III Ecoregions
- Which agricultural compounds go onto Sullivan County farmland, and roughly how muchUSGS NAWQA EPest county estimates
Inherited from a wider read
- The growing challenges every Missouri grower plans around — written at state scale, so they stay on the state guidefrom Missouri
What this page can’t tell you
- How the season shifts across Sullivan County — the ~208 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 Sullivan County's 414,708 acreswhy one lot differs from the next →
- Which of those 64 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 Sullivan Countyread your own land →