Union County, in Tennessee, sits in USDA hardiness zone 7b — a band that supports both cool-season staples and warm-season crops chosen to fit the local frost window.
On paper, cabbage, prickly pear, california poppy, and collard greens all suit these conditions — on the ground, soil, sun, and drainage make the final call.
Union County lies within Appalachia — a regional growing area with its own character.
Grounded in USDA PHZM 2023 · Growable Ground suitability scoring · NOAA 1991–2020 Climate Normals
Union County holds more than one microclimate.
Soils and elevations shift across Union 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 Union County — soil, climate, flood, and parcel records. How we handle your address.
No card required · your full report in seconds
Union County — the short answer
Union County, Tennessee: USDA zone 7b, about 225 days between hard freezes, across 143K acres.
- USDA zone
- 7b
- USDA PHZM 2023
- Last hard freeze (28°F)
- Mar 28
- NOAA 1991–2020 Climate Normals, 28°F
- First hard freeze (28°F)
- Nov 8
- NOAA 1991–2020 Climate Normals, 28°F
- Days between freezes
- ~225
- NOAA 1991–2020 Climate Normals, 28°F
- County area
- 143K 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 7b is Union County's average, not your lot's — a low corner or a tree line moves it. Against Union County's 225-day season, see what your own ground reads.
Heat and winter chill in Union County
Across a year, Union County accumulates about 3,872 growing degree days above 50°F, about 241 fewer than the middle Tennessee county — ahead of 24 of Tennessee’s 95 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.
Winter banks about 2,286 hours below 45°F, 227 more than the Tennessee middle of 2,059. Chill is what tells a fruit tree its dormancy is over, and it is set by climate rather than by anything you can build.
Grounded in PRISM Climate Group, Oregon State University — 1991–2020 monthly normals
Soil in Union County
Across Union County, the ground is predominantly Ultisols, where Clarksville, Fullerton, and Berks are the most extensive named soil series. The soil is generally well drained with a cherty silt loam surface. Topsoil pH runs about 4.8–5.3, very strongly acidic. Rainfall drains through hydrologic group B soils.
Soil order
Ultisols
Drainage
Well drained
Prime farmland
1%
Hydric soils
0%
Soil still varies lot by lot — soil types explained.
How the ground varies across Union County
The USDA soil survey maps 55% of Union County as well drained — but another 26% drains differently: 21% somewhat excessively drained, 5% moderately well drained.
Clarksville is the most extensive named soil at 26% of mapped acres, then Fullerton (23%) and Berks (11%).
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 Union County
Each reading below is measured for Union 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 Union 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 Union County runs about pH 4.8–5.3, on the acidic side.
Blueberries, potatoes, and rhododendrons thrive in it, but most vegetables start locking out nutrients below about pH 6.0 and grow pale and stunted no matter how much you feed them.
A measured lime application raises pH for the crops that need it — but test first, because the right rate depends on your own soil, not the county average.
USDA NRCS SSURGO
Season length
MeasuredUnion County runs about 225 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
MeasuredUnion County sits in USDA hardiness zone 7b.
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 Union County is in
Union County sits in the Ridge and Valley — EPA Level III, inside the wider Eastern Temperate Forests. One consistent ecological setting across the whole county.
What Grows in Union County
We scored all 1,086 plants against Union County's own USDA zone 7b and its own 225-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 Tennessee profile.
Is it too late to plant in Union County?
Usually not — gardeners here simply switch what goes in the ground as the season moves. Cool-season crops can go in from around Feb 28; tender transplants wait until two to three weeks after the last 28°F hard freeze, which lands near Mar 28 (NOAA 1991–2020 climate normals); and from midsummer, planting counts back from the first fall freeze around Nov 8 — long-season crops need about 90 days of runway, quick greens only 30. There is slack in a calendar like this — late plantings, second rounds of favorites, and a fall bench that keeps beds working.
Documented around Union County
Survey cells within 31 miles of Union County checked for spotted lanternfly, none carrying a detection — a surveyed negative, not an absence of looking. Nearest documented record 85 miles off. What to watch for.
- Japanese beetle1 documented records
Sighting records, so they follow observers as much as insects.
What gets applied to farmland in Union County
USGS estimates 1,470 lb of 2,4-d on Union County farmland in 2019, its largest by weight, ahead of Glyphosate (737 lb) and Atrazine (527 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 Union County — and how to grow with it.
We checked the federal record across Union County — 115 documented sites across 6 of the 9 source types we track.
The most significant on record: 4 Toxics Release Inventory facilities. Active industrial facilities reporting chemical releases to air, water, and land.
Union County carries one of the heavier federal records we track — and that's not a verdict on your yard. Proximity to a documented site is information, not a diagnosis: nothing here says any particular parcel is affected. It does earn one concrete step — before food beds go in the ground, a professional soil test tells you exactly what you're working with, and raised beds with clean imported soil grow well almost anywhere in the meantime.
Sources: EPA, USGS — 1.8M documented sites tracked nationwide across 9 federal source types.
What's on the federal record near Union County
Closest first, across Union County. Listing isn't leaking, and distance isn't exposure.
- MAYNARDVILLE WATER DEPTPFAS · 1.8 mi
- General MerchandiseUnderground Storage Tanks · 2.5 mi
- Cook's GroceryUnderground Storage Tanks · 2.5 mi
- Keck's Sports ShopUnderground Storage Tanks · 3.0 mi
- 33 Sports And Marina IncUnderground Storage Tanks · 3.0 mi
- Booker's One Stop no.2Underground Storage Tanks · 3.0 mi
- Food City Gas-N-Go No. 680Underground Storage Tanks · 3.1 mi
- 33 QuarryUnderground Storage Tanks · 3.1 mi
- Chuck Swan State ForestUnderground Storage Tanks · 3.1 mi
- TN0026Underground Storage Tanks · 3.1 mi
- Robbins' Service StationUnderground Storage Tanks · 3.2 mi
- Kays MarketUnderground Storage Tanks · 3.2 mi
6 more sites are on the record inside the same radius. See them on the map
Measured from Union 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 Union County.
Total Sites
115
across Union County
Risk Level
High
Highest-severity
4 Toxics Release Inventory facilities
Sources Checked
across Union County
Severity Distribution
across Union County
Highest-Severity Sites
A note from Gnorman
What an experienced grower watches for around here
In and around Union County, Mining runs higher than the national average — 47 sites across Union County. It's not cause for alarm — it's worth knowing, and there's a sensible way to grow around it.
Mining: Mining sites — both historic and active — can leach heavy metals (arsenic, lead, cadmium, mercury) into soil and water for centuries after operations cease.
Test soil for heavy metals (lead, arsenic, cadmium, mercury) — this is essential near any mining site.
Check your specific parcel in Union 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 Union County average
Your land is one point inside Union County
Everything above resolves to Union County as a whole — one PHZM band and one county frost record, read across 143K 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 Union County Average
Union County Average
- ●USDA Zones 7b, averaged across Union County
- ●One soil character for all of Union County
- ●Frost dates read at Union County's scale: Mar 28 to Nov 8
YOUR Parcel
- ✓Your exact zone, not Union County's 7b
- ✓Your SSURGO soil type & pH
- ✓Your sun exposure, cast in 3D
See MY Growing Report
Read your parcel in Union County
Pull a site-specific report for your exact address in Union County, Tennessee — soil, sun, drainage, frost risk, and scored plant recommendations.
Three things about your lot that Union County averages can't show:
We read public map data around Union County — soil, climate, flood, and parcel records. How we handle your address.
25+ data sources read at your address, not the Union County average
How we know this about Union 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 Union County carries no record of its own, the figure is inherited and labelled — the resolution ledger below names each.
Common questions about Union County
When does frost risk typically end in Union County?
The last hard freeze (28°F) in Union County typically lands around Mar 28, 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 18.
How long is the growing season in Union County?
Measured between 28°F hard freezes, Union County sees about 225 frost-free days — roughly Mar 28 through Nov 8, per NOAA 1991–2020 climate normals. Tender crops work a shorter one: nearer Apr 18 to Oct 25, about 190 days.
Is the soil safe to grow vegetables in Union County?
The federal record around Union County runs heavier than most — 115 documented sites, mostly Underground Storage Tanks entries (49), the nearest PFAS record about 1.8 miles out — so test the soil before planting food in the ground, and raised beds with clean imported soil grow well in the meantime. Even here, proximity to a documented site is information, not a diagnosis of any one yard; the contamination map shows exactly what's recorded and where.
Everything above is measured at Union County's scale — its 7b band and its 225-day season. Your yard writes its own version of Union 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 Tennessee's frost window, season length, and soil profile against the plant's real requirements.
What this page reads at Union County’s own scale
9 of the readings below were taken at Union County's own scale — its own ~225-day span between 28°F freezes, the 3 most extensive soil series mapped here and 115 documented sites inside its boundary; one is borrowed from a wider read, named and linked below.
Measured here
- Union County's own USDA hardiness band, zones 7bUSDA PHZM 2023
- Union County's own 28°F hard-freeze dates and its ~225-day span between themNOAA 1991–2020 Climate Normals
- The soil order, drainage, surface pH, and the 3 most extensive named soil series mapped in Union CountyUSDA NRCS SSURGO
- 115 documented contamination sites inside the county boundary, distance-sorted from its center — the closest PFAS record about 1.8 miles outFederal environmental registers
- Union County's boundary and the 143,093 acres inside itUS Census TIGER/Line 2025
- Which of 1,086 plants clear zones 7b and a ~225-day seasonGrowable Ground crop-matching engine
- Union County sitting wholly inside the Ridge and ValleyUS EPA Level III Ecoregions
- Open occurrence records documented in Union County for a tracked speciesGBIF derived datasets (CC0 / CC BY 4.0)
- Which agricultural compounds go onto Union County farmland, and roughly how muchUSGS NAWQA EPest county estimates
Inherited from a wider read
- The growing challenges every Tennessee grower plans around — written at state scale, so they stay on the state guidefrom Tennessee
What this page can’t tell you
- How the season shifts across Union County — the ~225 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 Union County's 143,093 acreswhy one lot differs from the next →
- Which of those 115 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 Union Countyread your own land →