Old Monroe, Missouri, sits in USDA hardiness zone 6b — a zone band wide enough that plant choice, not possibility, is the interesting question.
Growers here do well with cabbage, hazelnut, lavender, and collard greens — with the usual caveat that any single yard's soil, sun, and drainage cast the deciding vote.
Even in Old Monroe, 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 Old Monroe 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 Old Monroe — soil, climate, flood, and parcel records. How we handle your address.
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Old Monroe — the short answer
Old Monroe, Missouri: USDA zone 6b, about 225 days between hard freezes, across 232 acres of city.
- USDA zone
- 6b
- USDA PHZM 2023
- Last hard freeze (28°F)
- Mar 26
- NOAA 1991–2020 Climate Normals, 28°F — this town
- First hard freeze (28°F)
- Nov 6
- NOAA 1991–2020 Climate Normals, 28°F — this town
- Days between freezes
- ~225
- NOAA 1991–2020 Climate Normals, 28°F — this town
- City area
- 232 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 6b is Old Monroe's average, not your lot's — a low corner or a tree line moves it. Against Old Monroe's 225-day season, see what your own ground reads.
Soil varies lot by lot — soil types explained.
What this means for growing in Old Monroe
Each reading below is measured for Old Monroe itself — here is what it means for a garden here, and the move an experienced grower makes about it.
Season length
MeasuredOld Monroe 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
MeasuredOld Monroe sits in USDA hardiness zone 6b.
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 Old Monroe is in
Old Monroe sits in the Interior River Valleys and Hills — EPA Level III, inside the wider Eastern Temperate Forests. That is read at Old Monroe's own centroid rather than borrowed from Lincoln County.
What Grows in Old Monroe
Every plant below cleared Old Monroe's own zone 6b and its 225-day season. Each card opens that plant's Missouri profile. How we score.
Is it too late to plant in Old Monroe?
Almost never — the real question is what to plant next. Cool-season crops can go in from around Feb 26; tender transplants wait until two to three weeks after the last 28°F hard freeze, which lands near Mar 26 (NOAA 1991–2020 climate normals); and from midsummer, planting counts back from the first fall freeze around Nov 6 — long-season crops need about 90 days of runway, quick greens only 30. A long window like this one runs successions deep into fall — and even its last weeks take quick greens and garlic.
Documented around Old Monroe
Survey cells within 31 miles of Old Monroe checked for spotted lanternfly, none carrying a detection — a surveyed negative, not an absence of looking. Nearest documented record 239 miles off. What to watch for.
What's on the federal record near Old Monroe
Closest first, within ~10 miles of Old Monroe. Listing isn't leaking, and distance isn't exposure.
- SCHADER MERCANTILEUnderground Storage Tanks · 900 ft
- OLD MONROE ELEV & SUPPLY COUnderground Storage Tanks · 1200 ft
- OLD MONROE 66Underground Storage Tanks · 1300 ft
- ROBERT E. PHELPSUnderground Storage Tanks · 1500 ft
- CROWN SERVICE INCUnderground Storage Tanks · 1600 ft
- MID-WESTERN VETERINARY SUPPLYUnderground Storage Tanks · 1600 ft
- T48N R02ENitrate · 2300 ft
- FASTLANE OLD MONROEUnderground Storage Tanks · 2300 ft
- T48N R02E 12BBD1Nitrate · 0.6 mi
- KIMATERIAL, INC.Underground Storage Tanks · 1.2 mi
- GALLOWAY EQUIPMENT COMPANY, INCUnderground Storage Tanks · 1.2 mi
- T48N R03E 07ABC1Nitrate · 1.8 mi
6 more sites are on the record inside the same radius. See them on the map
Measured from Old Monroe'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 Old Monroe.
Sources Checked
within ~10 miles of Old Monroe
Severity Distribution
within ~10 miles of Old Monroe
Highest-Severity Sites
A note from Gnorman
What an experienced grower watches for around here
In and around Old Monroe, Toxics Release Inventory runs higher than the national average — 24 sites within ~10 miles of Old Monroe. That's not a problem with your land — it's information about it.
Toxics Release Inventory: TRI facilities report annual chemical releases to air, water, and land.
Check prevailing wind direction — downwind parcels face higher exposure than upwind or crosswind locations.
Check your specific parcel in Old Monroe
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 Old Monroe average
Your land is one point inside Old Monroe
Everything above resolves to Old Monroe as a whole — one PHZM band and one 28°F frost record, read across 232 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 city 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 Old Monroe Average
Old Monroe Average
- ●USDA Zones 6b, averaged across Old Monroe
- ●One soil character for all of Old Monroe
- ●Frost dates read at Old Monroe's scale: Mar 26 to Nov 6
YOUR Parcel
- ✓Your exact zone, not Old Monroe's 6b
- ✓Your SSURGO soil type & pH
- ✓Your sun exposure, cast in 3D
See MY Growing Report
Read your specific parcel in Old Monroe
Pull a site-specific report for your exact address in Old Monroe, Missouri — soil, sun, drainage, frost risk, and scored plant recommendations.
Three things about your lot that Old Monroe averages can't show:
We read public map data around Old Monroe — soil, climate, flood, and parcel records. How we handle your address.
25+ data sources read at your address, not the Old Monroe average
How we know this about Old Monroe
The datasets: hardiness from the USDA ARS Plant Hardiness Zone Map 2023, read at this city’s own centroid; hard-freeze dates from NOAA 1991–2020 28°F normals at Old Monroe’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 city grain anywhere on this page — there is no city-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 Old Monroe
When does frost risk typically end in Old Monroe?
The last hard freeze (28°F) in Old Monroe typically lands around Mar 26, 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 16.
When is the first frost in Old Monroe?
The first hard freeze (28°F) in Old Monroe typically arrives around Nov 6, per NOAA 1991–2020 climate normals — the point tender summer crops finish. Lighter frosts run ahead of it, near Oct 23, so the watching starts about Oct 7 — about 225 days after the spring freeze cleared.
How long is the growing season in Old Monroe?
Measured between 28°F hard freezes, Old Monroe sees about 225 frost-free days — roughly Mar 26 through Nov 6, per NOAA 1991–2020 climate normals. Tender crops work a shorter one: nearer Apr 16 to Oct 23, about 190 days.
Is the soil safe to grow vegetables in Old Monroe?
The federal record around Old Monroe is a meaningful one — 285 documented sites, mostly Underground Storage Tanks entries (125), the nearest Underground Storage Tanks record about 0.2 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.
How do I protect my plants from frost in Old Monroe?
From about Oct 7 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 Nov 6 (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 Nov 6. Hardy greens and roots shrug off light frost and sweeten after it — leave them in.
Everything above is measured at Old Monroe's scale — its 6b band and its 225-day season. Your yard writes its own version of Old Monroe'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 Old Monroe’s own scale
7 of the readings below were taken at Old Monroe's own scale — its own ~225-day season between 28°F freezes, the 232 acres it covers and 285 documented sites around it; 4 are borrowed from a wider read, named and linked below.
Measured here
- Old Monroe's own USDA hardiness band, zones 6bUSDA PHZM 2023
- Old Monroe's own 28°F hard-freeze dates, about Mar 26 and Nov 6 and the ~225-day span between themNOAA 1991–2020 Climate Normals
- 285 documented contamination sites on the federal record near Old Monroe, the closest Underground Storage Tanks record about 0.2 miles out from the town centreFederal environmental registers
- Old Monroe's boundary and the 232 acres inside itUS Census TIGER/Line 2025
- Which of 1,086 plants clear zones 6b and a ~225-day seasonGrowable Ground crop-matching engine
- The ecoregion at Old Monroe's own centroid, the Interior River Valleys and HillsUS EPA Level III Ecoregions
- Lanternfly survey cells around Old Monroe checked, none carrying a detectionlydemapr (De Bona & Helmus), 10 km survey lattice
Inherited from a wider read
- Soil character — no town-scale survey exists, so Old Monroe's 232 acres read through its county's SSURGO summaryfrom Lincoln County
- Growing-degree days and winter chill — measured county-wide only, so the county page carries themfrom Lincoln 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 Lincoln County
What this page can’t tell you
- The soil pH, drainage, sun hours, and frost pockets on any one lot among Old Monroe's 232 acreswhy one lot differs from the next →
- Which side of Old Monroe you're on — a low spot frosts first and a south wall warms early, and one normal is being asked to speak for all 232 acresreading your own microclimate →
- How close that record sits to YOUR lot — the closest Underground Storage Tanks record about 0.2 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 Old Monroe-wide figureread your own land →
More in Missouri
Wider growing context
What grows across MissouriOld Monroe sits outside our named growing regions, so Missouri as a whole is its closest context here.
Nearby growing guides