Union Star, Missouri, sits in USDA hardiness zone 6a — a range where zone-matched perennials and frost-aware annual timing set what succeeds.
Among the crops suited to this profile: cabbage, hazelnut, lavender, and collard greens. The site-level story — soil, sun, drainage — decides the rest.
Even in Union Star, no two yards are alike.
A low spot, a south-facing slope, or a stand of trees moves the frost date and sun across a single Union Star lot. 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 Star — soil, climate, flood, and parcel records. How we handle your address.
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Union Star — the short answer
Union Star, Missouri: USDA zone 6a, about 208 days between hard freezes, across 168 acres of town.
- USDA zone
- 6a
- USDA PHZM 2023
- Last hard freeze (28°F)
- Apr 6
- NOAA 1991–2020 Climate Normals, 28°F — this town
- First hard freeze (28°F)
- Oct 31
- NOAA 1991–2020 Climate Normals, 28°F — this town
- Days between freezes
- ~208
- NOAA 1991–2020 Climate Normals, 28°F — this town
- Town area
- 168 acres
- US Census TIGER/Line 2025
Every figure names the dataset it came from. Hard-freeze dates are this town’s own 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 Union Star's average, not your lot's — a low corner or a tree line moves it. Against Union Star's 208-day season, see what your own ground reads.
Soil varies lot by lot — soil types explained.
What this means for growing in Union Star
Each reading below is measured for Union Star itself — here is what it means for a garden here, and the move an experienced grower makes about it.

Season length
MeasuredUnion Star 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
MeasuredUnion Star 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 Union Star is in
Union Star sits in the Central Irregular Plains — EPA Level III, inside the wider Great Plains. That is read at Union Star's own centroid rather than borrowed from DeKalb County.
What Grows in Union Star
Every plant below cleared Union Star's own zone 6a and its 208-day season. Each card opens that plant's Missouri profile. How we score.






























Is it too late to plant in Union Star?
Usually not — gardeners here simply switch what goes in the ground as the season moves. Cool-season crops can go in from around Mar 9; tender transplants wait until two to three weeks after the last 28°F hard freeze, which lands near Apr 6 (NOAA 1991–2020 climate normals); and from midsummer, planting counts back from the first fall freeze around Oct 31 — 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.
What's on the federal record near Union Star
Closest first, within ~10 miles of Union Star. Listing isn't leaking, and distance isn't exposure.
- STAR ONE STOPBrownfields · 600 ft
- STAR ONE STOPUnderground Storage Tanks · 700 ft
- CLOSED SERVICE STATIONUnderground Storage Tanks · 1000 ft
- T60N R33W 34ABB1Nitrate · 0.6 mi
- NATIONAL ARCHIVES AND RECORDS ADMINISTRATIONUnderground Storage Tanks · 2.3 mi
- HELENAUnderground Storage Tanks · 4.1 mi
- AT&TBrownfields · 4.2 mi
- T60N R32W 28DDC1Nitrate · 5.2 mi
- GILLETT SERVICE STATION INCUnderground Storage Tanks · 5.4 mi
- KING CITY MAINT LOTUnderground Storage Tanks · 5.5 mi
- SUR-GRO PLANT FOOD, INCUnderground Storage Tanks · 5.6 mi
- LIPPARD GENERAL STOREUnderground Storage Tanks · 5.7 mi
6 more sites are on the record inside the same radius. See them on the map
Measured from Union Star'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 Star.
Sources Checked
within ~10 miles of Union Star
Severity Distribution
within ~10 miles of Union Star
Highest-Severity Sites

A note from Gnorman
What an experienced grower watches for around here
In and around Union Star, Nitrate runs higher than the national average — 10 sites within ~10 miles of Union Star. 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 Union Star
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 Star average
Your land is one point inside Union Star
Everything above resolves to Union Star as a whole — one PHZM band and one 28°F frost record, read across 168 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 town 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 local average.
Your Lot vs the Union Star Average
Union Star Average
- ●USDA Zones 6a, averaged across Union Star
- ●One soil character for all of Union Star
- ●Frost dates read at Union Star's scale: Apr 6 to Oct 31
YOUR Parcel
- ✓Your exact zone, not Union Star's 6a
- ✓Your SSURGO soil type & pH
- ✓Your sun exposure, cast in 3D
See MY Growing Report
Read your specific parcel in Union Star
Pull a site-specific report for your exact address in Union Star, Missouri — soil, sun, drainage, frost risk, and scored plant recommendations.
Three things about your lot that Union Star averages can't show:
We read public map data around Union Star — soil, climate, flood, and parcel records. How we handle your address.
25+ data sources read at your address, not the Union Star average
How we know this about Union Star
The datasets: hardiness from the USDA ARS Plant Hardiness Zone Map 2023, read at this town’s own centroid; hard-freeze dates from NOAA 1991–2020 28°F normals at Union Star’s own record; boundaries and acreage from US Census TIGER/Line 2025; the contamination records from the federal sources named in their beats above. Soil is not read at town grain anywhere on this page — there is no town-resolution survey in our data, which is why you will find no soil grid here rather than a statewide one wearing a local label. The resolution ledger below names every figure this page inherited.
Common questions about Union Star
When does frost risk typically end in Union Star?
The last hard freeze (28°F) in Union Star typically lands around Apr 6, 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 27.
When is the first frost in Union Star?
The first hard freeze (28°F) in Union Star typically arrives around Oct 31, per NOAA 1991–2020 climate normals — the point tender summer crops finish. Lighter frosts run ahead of it, near Oct 17, so the watching starts about Oct 1 — about 208 days after the spring freeze cleared.
How long is the growing season in Union Star?
Measured between 28°F hard freezes, Union Star sees about 208 frost-free days — roughly Apr 6 through Oct 31, per NOAA 1991–2020 climate normals. Tender crops work a shorter one: nearer Apr 27 to Oct 17, about 173 days.
Is the soil safe to grow vegetables in Union Star?
The federal record around Union Star is light — 29 documented sites across the 9 federal source types we checked, mostly Underground Storage Tanks entries (17), the nearest Brownfields record about 0.1 miles out — and proximity to a documented site is information, not a diagnosis of any one yard. Growing food here starts from a strong position; a soil test before new food beds settles any site-specific question.
How do I protect my plants from frost in Union Star?
From about Oct 1 the job here turns from planting to protecting — the last start even a 30-day crop can finish. As the season closes around the first 28°F hard freeze near Oct 31 (NOAA 1991–2020 climate normals), three moves buy time: row cover or an old sheet over tender plants on still, clear nights; water the soil the afternoon before a freeze, so it holds warmth overnight; and harvest tomatoes, peppers and basil before Oct 31. Hardy greens and roots shrug off light frost and sweeten after it — leave them in.
Everything above is measured at Union Star's scale — its 6a band and its 208-day season. Your yard writes its own version of Union Star's numbers: we read soil, sun, drainage and frost at your exact address. Try it for 14 days — no card required.
What this page reads at Union Star’s own scale
6 of the readings below were taken at Union Star's own scale — its own ~208-day season between 28°F freezes, the 168 acres it covers and 29 documented sites around it; 4 are borrowed from a wider read, named and linked below.
Measured here
- Union Star's own USDA hardiness band, zones 6aUSDA PHZM 2023
- Union Star's own 28°F hard-freeze dates, about Apr 6 and Oct 31 and the ~208-day span between themNOAA 1991–2020 Climate Normals
- 29 documented contamination sites on the federal record near Union Star, the closest Brownfields record about 0.1 miles out from the town centreFederal environmental registers
- Union Star's boundary and the 168 acres inside itUS Census TIGER/Line 2025
- Which of 1,086 plants clear zones 6a and a ~208-day seasonGrowable Ground crop-matching engine
- The ecoregion at Union Star's own centroid, the Central Irregular PlainsUS EPA Level III Ecoregions
Inherited from a wider read
- Soil character — no town-scale survey exists, so Union Star's 168 acres read through its county's SSURGO summaryfrom DeKalb County
- Growing-degree days and winter chill — measured county-wide only, so the county page carries themfrom DeKalb County
- The growing challenges every Missouri grower plans around — written at state scale, so they stay on the state guidefrom Missouri
- Butterfly and beetle records, and the farmland pesticide estimate — all published county-widefrom DeKalb County
What this page can’t tell you
- The soil pH, drainage, sun hours, and frost pockets on any one lot among Union Star's 168 acreswhy one lot differs from the next →
- Which side of Union Star you're on — a low spot frosts first and a south wall warms early, and one normal is being asked to speak for all 168 acresreading your own microclimate →
- How close that record sits to YOUR lot — the closest Brownfields record about 0.1 miles out, measured from the town centrehow we read the record →
- Where cold air settles, which slopes face the sun, and which way the wind runs on your own ground — measured at your address, and averaged away by any Union Star-wide figureread your own land →
More in Missouri
Wider growing context
What grows across MissouriUnion Star sits outside our named growing regions, so Missouri as a whole is its closest context here.
Nearby growing guides
