Data: 2023 USDA zones (PRISM/OSU) · NOAA 1991–2020 normals · updated

Planting zone for 63544 — Green Castle, MO

ZIP code 63544 (Green Castle, Sullivan County) is in USDA zone 6a: the coldest winter night averages −10 to −5 °F. The median last spring frost is April 26 and the first fall frost October 14.

Where ZIP 63544 is

Outlined: the ZIP code area · tap the map for the zone at any spot · scroll or pinch to zoom

Not the official USDA Plant Hardiness Zone Map. Zones come from the 2023 USDA hardiness-zone data by the PRISM Group, Oregon State University; we re-mapped and recolored them. The official map is at planthardiness.ars.usda.gov.

Zone6a−10 to −5 °F
Coldest night−23.3 to −20.6 °C
Last frostApr 26
First frostOct 14
2012 zone5b

Was 5b on the 2012 map — half a zone warmer now. The zone is the one at the center of the ZIP code; hilly ZIPs can span two zones. What zone 6a means →

Frost forecast — next 7 nights

live from the National Weather Service

Loading the forecast for Green Castle, MO…

Forecast data: National Weather Service (api.weather.gov), public domain. This is not a warning service — for official frost and freeze warnings see weather.gov.

Frost dates in Green Castle, MO

JanFebMarAprMayJunJulAugSepOctNovDec
Blue: frost possible · fading green: frost risk falling or rising (90% → 10%) · green: frost-free
Last spring frostApril 26median — 50% chance of a later frost
Safe for tender plantsMay 12only 10% chance of frost after
First fall frostOctober 14median — 10% chance by Sep 30
Growing season169 daysfrost-free, median

A hard freeze (28 °F) usually ends around April 14 and returns around October 24.

From the NOAA station Green City 5n, MO — 9 miles away, elevation 1,037 ft. NOAA NCEI U.S. Climate Normals 1991–2020, 32 °F threshold. Low spots and valleys can freeze later in spring than the station.

When to plant vegetables in 63544

JanFebMarAprMayJunJulAugSepOctNovDec
PeasSow outdoors · Mar 15 – Mar 29
SpinachSow outdoors · Mar 15 – Apr 5
Broccoli, cabbageStart indoors · Feb 15 – Mar 1
Broccoli, cabbageTransplant · Apr 5 – Apr 19
Onion setsPlant outdoors · Mar 29 – Apr 12
PotatoesPlant outdoors · Apr 5 – Apr 19
LettuceSow outdoors · Mar 29 – Apr 12
Carrots, beetsSow outdoors · Apr 5 – Apr 19
TomatoesStart indoors · Mar 1 – Mar 15
TomatoesTransplant · May 3 – May 17
Peppers, eggplantStart indoors · Feb 15 – Mar 1
Peppers, eggplantTransplant · May 10 – May 24
BeansSow outdoors · May 3 – May 17
Sweet cornSow outdoors · May 3 – May 17
Cucumbers, squashSow outdoors · May 3 – May 17
Fall lettuce, spinachSow outdoors · Aug 19 – Sep 2
GarlicPlant cloves · Sep 30 – Nov 4
Start seeds indoorsSow or plant outdoorsFall plantingMedian last & first frost

Counted from the median last spring frost (Apr 26) and first fall frost (Oct 14) with the rules of thumb U.S. extension services publish. Cool-season crops take a light frost; warm-season crops do best once the soil is above about 60 °F.

When spring arrived in 2026

In 2026, spring leaf-out near 63544 came on Mar 11 — 17 days earlier than the 1991–2020 average (Mar 28).

JanFebMarAprMayJun

The Spring Index marks the day when accumulated warmth is enough for lilac and honeysuckle to leaf out — a widely used signal that the growing season has started. Source: USA National Phenology Network, www.usanpn.org — Spring Indices, first leaf, 2026 (data as of 2026-09-08) and 30-year average 1991–2020 (CC BY 4.0).

Native plants for zone 6a in Missouri

516 plants native to the lower 48 states, recorded in Missouri, and rated by the USDA to survive −10 °F or colder — the bottom of zone 6a. Each links to its USDA PLANTS profile.

Trees 68

American basswood100 ft · blooms late spring · low shade tolerance · to −46 °FAmerican beech80 ft · blooms mid spring · low shade tolerance · to −44 °FAmerican chestnut115 ft · blooms early summer · high shade tolerance · to −33 °FAmerican elm120 ft · blooms early spring · medium shade tolerance · to −46 °FAmerican sycamore100 ft · blooms spring · medium shade tolerance · to −34 °Fbald cypress130 ft · blooms mid spring · medium shade tolerance · to −18 °F

Shrubs 82

alternateleaf dogwood25 ft · blooms mid spring · low shade tolerance · to −47 °FAmerican black currant3 ft · blooms early spring · to −46 °FAmerican hazelnut10 ft · blooms spring · medium shade tolerance · to −33 °FAmerican holly40 ft · blooms mid spring · low shade tolerance · to −20 °FAmerican hornbeam30 ft · blooms mid spring · low shade tolerance · to −34 °FAmerican plum24 ft · blooms mid spring · high shade tolerance · to −38 °F

Wildflowers & perennials 190

alkali buttercup1 ft · blooms late spring · low shade tolerance · to −38 °FAmerican bur-reed3 ft · blooms indeterminate · medium shade tolerance · to −33 °FAmerican eelgrass1 ft · blooms mid summer · high shade tolerance · to −33 °FAmerican licorice4 ft · blooms late spring · medium shade tolerance · to −38 °FAmerican lotus3 ft · blooms mid summer · high shade tolerance · to −36 °FAmerican pokeweed7 ft · blooms mid summer · low shade tolerance · to −33 °F

Grasses 155

alkali sacaton3 ft · blooms mid summer · high shade tolerance · to −38 °FAmerican cupscale3 ft · blooms early summer · high shade tolerance · to −18 °Fawlfruit sedge4 ft · blooms mid spring · low shade tolerance · to −38 °FBicknell's sedge3 ft · blooms late spring · low shade tolerance · to −38 °Fbig bluestem6 ft · blooms summer · high shade tolerance · to −46 °Fblister sedge3 ft · blooms late spring · medium shade tolerance · to −38 °F

Vines 10

American bittersweet15 ft · blooms spring · low shade tolerance · to −38 °Fcatbird grape30 ft · blooms late spring · medium shade tolerance · to −13 °Fdevil's darning needles15 ft · blooms mid summer · medium shade tolerance · to −38 °Ffrost grape83 ft · blooms late spring · medium shade tolerance · to −23 °Fmuscadine30 ft · blooms late spring · medium shade tolerance · to −18 °Friverbank grape45 ft · blooms late spring · medium shade tolerance · to −33 °F

Source: USDA, NRCS. 2026. The PLANTS Database (plants.usda.gov), National Plant Data Team — state distribution, native status and the “Temperature, Minimum” characteristic. Check light, moisture and soil needs before buying; local nurseries and your state native plant society can confirm what thrives in Green Castle, MO.

Soil in Green Castle, MO

The soil mapped at the center of ZIP 63544 is Armstrong — clay loam, somewhat poorly drained.

TextureClay loamholds water and nutrients; slow to drain and warm up
pH6.5neutral; most vegetables like 6.0–7.0
DrainageSomewhat poorly drainedconsider raised beds
Organic matter1.5%low — add compost
Hydrologic groupDwater soaks in very slowly
Farmland classNot prime farmlandUSDA classification

Map unit: Armstrong clay loam, 9 to 14 percent slopes, moderately eroded.

Soil Survey Staff, Natural Resources Conservation Service, USDA. Soil Survey Geographic (SSURGO) Database, via Soil Data Access, accessed 2026-10-29. The soil at the center point of ZIP 63544; soils change within a few hundred feet, so a home soil test (pH, nutrients) is still the best guide.

Climate in Green Castle, MO

Summer high85 °Faverage high, July
Winter low13 °Faverage low, January
Hot days25days a year at 90 °F or more
Freezing nights139nights a year at 32 °F or less
Growing degree days3,140base 50 °F — the season’s usable heat
Longest day15 h 02 mindaylight on June 21
Shortest day9 h 18 mindaylight on December 21
Onions to growLong-daysummer days reach 15+ hours, enough for long-day varieties (intermediate types work too)
Precipitation40.7 inper year, rain and melted snow

Average high and low, by month

0°10°20°30°40°50°60°70°80°90°100°32 °FJanuary: average high 32 °F, low 13 °F 32°13° JanFebruary: average high 37 °F, low 17 °F 37°17° FebMarch: average high 50 °F, low 28 °F 50°28° MarApril: average high 62 °F, low 38 °F 62°38° AprMay: average high 71 °F, low 49 °F 71°49° MayJune: average high 81 °F, low 59 °F 81°59° JunJuly: average high 85 °F, low 63 °F 85°63° JulAugust: average high 84 °F, low 61 °F 84°61° AugSeptember: average high 77 °F, low 52 °F 77°52° SepOctober: average high 64 °F, low 40 °F 64°40° OctNovember: average high 50 °F, low 29 °F 50°29° NovDecember: average high 37 °F, low 19 °F 37°19° Dec

Precipitation by month inches

0″1″2″3″4″5″6″January: 1.34 in precipitation 1.3 JanFebruary: 1.70 in precipitation 1.7 FebMarch: 2.56 in precipitation 2.6 MarApril: 3.87 in precipitation 3.9 AprMay: 5.57 in precipitation 5.6 MayJune: 5.25 in precipitation 5.3 JunJuly: 4.51 in precipitation 4.5 JulAugust: 4.75 in precipitation 4.8 AugSeptember: 4.21 in precipitation 4.2 SepOctober: 3.04 in precipitation 3.0 OctNovember: 2.25 in precipitation 2.3 NovDecember: 1.69 in precipitation 1.7 Dec

NOAA NCEI U.S. Climate Normals 1991–2020 — temperature: Green City 5n, MO (9 mi away); precipitation: Green City 5n, MO (9 mi away). Daylight is calculated from latitude.

Nearby ZIP codes

3 of the 8 nearest ZIP codes are in a different zone — elevation and distance from water change winter lows quickly.

635596a
Novinger, MO · 4 mi
635455b
Green City, MO · 6 mi
635676a
Worthington, MO · 14 mi
635566a
Milan, MO · 15 mi
635016a
Kirksville, MO · 15 mi
635666a
Winigan, MO · 16 mi
635605b
Pollock, MO · 16 mi
635655b
Unionville, MO · 17 mi

Missouri planting zones →

Questions about 63544

What planting zone is ZIP code 63544?

ZIP code 63544 (Green Castle, MO) is in USDA hardiness zone 6a on the 2023 map: the coldest night of an average winter reaches −10 to −5 °F (−23.3 to −20.6 °C).

When is the last frost in Green Castle, MO?

The median last spring frost (32 °F) near 63544 is April 26; after May 12 there is only a 10% chance of frost. Data: NOAA 1991–2020 normals, Green City 5n station.

When is the first frost in Green Castle, MO?

The median first fall frost near 63544 is October 14, giving a median frost-free growing season of 169 days.

When should I plant tomatoes in 63544?

Start tomato seeds indoors around Mar 1 – Mar 15 and set transplants outside around May 3 – May 17, one to three weeks after the median last frost.

How much rain and snow does 63544 get?

About 40.7 inches of precipitation a year (NOAA 1991–2020 normals, Green City 5n station).

How hot do summers get in Green Castle, MO?

The average high peaks at 85 °F in July, with about 25 days a year at 90 °F or more.

What kind of soil does 63544 have?

The USDA soil survey maps Armstrong at the center of ZIP 63544: clay loam, somewhat poorly drained, pH about 6.5 (neutral).

Did spring come early in Green Castle, MO in 2026?

Spring leaf-out near 63544 came on Mar 11 in 2026, 17 days earlier than the 1991–2020 average (Mar 28), according to the USA National Phenology Network Spring Index.

What kind of onions grow in Green Castle, MO?

Long-day onions: the longest day near 63544 is 15 h 02 min, so summer days reach 15+ hours, enough for long-day varieties (intermediate types work too).

Did the zone for 63544 change?

Yes. The 2012 USDA map put 63544 in zone 5b; the 2023 map puts it in zone 6a. The newer map uses 1991–2020 data and more weather stations.