Data: 2023 USDA zones (PRISM/OSU) · NOAA 1991–2020 normals · updated Oct 29, 2026

Planting zone for 73556 — Martha, OK

ZIP code 73556 (Martha, Jackson County) is in USDA zone 7b: the coldest winter night averages 5 to 10 °F. The median last spring frost is April 10 and the first fall frost October 29.

Where ZIP 73556 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.

Zone7b5 to 10 °F

Coldest night−15 to −12.2 °C

Last frostApr 10

First frostOct 29

2012 zone7b

Same zone as on the 2012 map. The zone is the one at the center of the ZIP code; hilly ZIPs can span two zones. What zone 7b means →

Frost forecast — next 7 nights

live from the National Weather Service

Loading the forecast for Martha, OK…

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 Martha, OK

JanFebMarAprMayJunJulAugSepOctNovDec

Blue: frost possible · fading green: frost risk falling or rising (90% → 10%) · green: frost-free

Last spring frostApril 10median — 50% chance of a later frost

Safe for tender plantsApril 27only 10% chance of frost after

First fall frostOctober 29median — 10% chance by Oct 16

Growing season201 daysfrost-free, median

A hard freeze (28 °F) usually ends around March 31 and returns around November 5.

From the NOAA station Mangum 5se Mesonet, OK — 8 miles away, elevation 1,509 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 73556

JanFebMarAprMayJunJulAugSepOctNovDec

PeasSow outdoors · Feb 27 – Mar 13

SpinachSow outdoors · Feb 27 – Mar 20

Broccoli, cabbageStart indoors · Jan 30 – Feb 13

Broccoli, cabbageTransplant · Mar 20 – Apr 3

Onion setsPlant outdoors · Mar 13 – Mar 27

PotatoesPlant outdoors · Mar 20 – Apr 3

LettuceSow outdoors · Mar 13 – Mar 27

Carrots, beetsSow outdoors · Mar 20 – Apr 3

TomatoesStart indoors · Feb 13 – Feb 27

TomatoesTransplant · Apr 17 – May 1

Peppers, eggplantStart indoors · Jan 30 – Feb 13

Peppers, eggplantTransplant · Apr 24 – May 8

BeansSow outdoors · Apr 17 – May 1

Sweet cornSow outdoors · Apr 17 – May 1

Cucumbers, squashSow outdoors · Apr 17 – May 1

Fall lettuce, spinachSow outdoors · Sep 3 – Sep 17

GarlicPlant cloves · Oct 15 – Nov 19

Start seeds indoorsSow or plant outdoorsFall plantingMedian last & first frost

Counted from the median last spring frost (Apr 10) and first fall frost (Oct 29) 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 73556 came on Feb 12 — 7 days earlier than the 1991–2020 average (Feb 19).

average
Feb 192026
Feb 12

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 7b in Oklahoma

518 plants native to the lower 48 states, recorded in Oklahoma, and rated by the USDA to survive 5 °F or colder — the bottom of zone 7b. Each links to its USDA PLANTS profile.

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 Martha, OK.

Soil in Martha, OK

The soil mapped at the center of ZIP 73556 is Roark — loam, well drained.

TextureLoama good balance for most vegetables

pH7.0neutral; most vegetables like 6.0–7.0

DrainageWell drainednatural drainage class

Organic matter2%moderate

Hydrologic groupCwater soaks in slowly

Farmland classprime farmlandUSDA classification

Map unit: Roark loam, 0 to 1 percent slopes.

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 73556; soils change within a few hundred feet, so a home soil test (pH, nutrients) is still the best guide.

Climate in Martha, OK

Summer high96 °Faverage high, July

Winter low24 °Faverage low, January

Hot days105days a year at 90 °F or more

Freezing nights97nights a year at 32 °F or less

Growing degree days5,091base 50 °F — the season’s usable heat

Longest day14 h 29 mindaylight on June 21

Shortest day9 h 49 mindaylight on December 21

Onions to growIntermediateday-neutral types bulb best; long-day varieties may not bulb fully

Precipitation29 inper year, rain and melted snow

Average high and low, by month

Precipitation by month inches

NOAA NCEI U.S. Climate Normals 1991–2020 — temperature: Mangum 5se Mesonet, OK (8 mi away); precipitation: Altus 4.8 Nnw, OK (3 mi away). Daylight is calculated from latitude.

Nearby ZIP codes

All 8 nearest ZIP codes share zone 7b.

Oklahoma planting zones →

Questions about 73556

What planting zone is ZIP code 73556?

ZIP code 73556 (Martha, OK) is in USDA hardiness zone 7b on the 2023 map: the coldest night of an average winter reaches 5 to 10 °F (−15 to −12.2 °C).

When is the last frost in Martha, OK?

The median last spring frost (32 °F) near 73556 is April 10; after April 27 there is only a 10% chance of frost. Data: NOAA 1991–2020 normals, Mangum 5se Mesonet station.

When is the first frost in Martha, OK?

The median first fall frost near 73556 is October 29, giving a median frost-free growing season of 201 days.

When should I plant tomatoes in 73556?

Start tomato seeds indoors around Feb 13 – Feb 27 and set transplants outside around Apr 17 – May 1, one to three weeks after the median last frost.

How much rain and snow does 73556 get?

About 29 inches of precipitation a year (NOAA 1991–2020 normals, Altus 4.8 Nnw station).

How hot do summers get in Martha, OK?

The average high peaks at 96 °F in July, with about 105 days a year at 90 °F or more.

What kind of soil does 73556 have?

The USDA soil survey maps Roark at the center of ZIP 73556: loam, well drained, pH about 7.0 (neutral).

Did spring come early in Martha, OK in 2026?

Spring leaf-out near 73556 came on Feb 12 in 2026, 7 days earlier than the 1991–2020 average (Feb 19), according to the USA National Phenology Network Spring Index.

What kind of onions grow in Martha, OK?

Intermediate onions: the longest day near 73556 is 14 h 29 min, so day-neutral types bulb best; long-day varieties may not bulb fully.