Soil Types in Oklahoma

Oklahoma has 579 zip codes in our database. The most common soil type is Loam, found in 0% of the state. Understanding your local soil type helps you choose the right plants and amendments for your garden.

Oklahoma spans USDA hardiness zones 6b through 8a. Your hardiness zone determines which perennial plants will survive winter in your area. Enter your zip code above to find your exact zone and get personalized planting recommendations.

Oklahoma's soils transition from east to west as rainfall decreases from 55 inches to 15 inches. Eastern Oklahoma has acidic, forest-derived soils in the Ouachita Mountains and Ozark Plateau — red and yellow clays with moderate fertility. Central Oklahoma's Cross Timbers region, named for the oak-woodland belt, has sandy and loamy soils over red sandstone and shale. The state's western third has short-grass prairie soils — thinner, alkaline, and adapted to drought. Port silt loam, the state soil, is a deep, productive alluvial soil found along the Washita River and other major streams. The Red River Valley along the Texas border has distinctive red clay colored by iron-rich Permian-age sedimentary rock. Oklahoma's famous red soil stains everything it contacts.

Oklahoma's growing season is relatively generous, ranging from 185 days in the northeast to 225 days in the southwest. Oklahoma City averages about 210 frost-free days, with the last spring frost near March 28 and first fall frost around October 25. Tulsa has about 205 days. The panhandle, at higher elevation and further north, has about 180 days. Oklahoma's weather is volatile — the state experiences more tornadoes per square mile than anywhere else, and late spring hailstorms can devastate gardens. Temperature swings of 30-40°F within 24 hours are common in spring. Despite these challenges, the long warm season produces excellent harvests when gardens are managed around the weather patterns.

Oklahoma's warm climate and varied soils support diverse gardening. Okra is the signature crop — the name even starts the same way — and thrives in the summer heat that exceeds 100°F for weeks in western Oklahoma. Southern peas (black-eyed, purple hull, crowder) are heat-loving staples. Tomatoes planted in March produce heavily before summer heat slows them, then often produce a second flush in fall. Watermelon and cantaloupe love the hot, sandy soils of western and central Oklahoma. Pecans are a major commercial crop, particularly in the river bottomlands. Wheat dominates western Oklahoma agriculture. For home gardens, successive plantings take advantage of the long season: spring cool crops, summer heat-lovers, and fall cool crops again.

Oklahoma State University Extension provides soil testing through county offices for about $10 — an excellent value. Oklahoma soils range widely in pH: eastern soils tend acidic (5.0-6.0), central soils are near-neutral, and western soils are alkaline (7.5-8.0). The red clay soils of central Oklahoma are iron-rich and fertile but compact easily. Adding gypsum and organic matter improves their workability. Sandy soils in western Oklahoma need organic matter for water retention. Wind is a significant factor statewide — mulch prevents both erosion and moisture loss. Oklahoma's intense summer heat bakes unmulched soil to temperatures that kill beneficial organisms and damage shallow roots.