Soil Guide

Soil is the foundation of your garden and provides just about everything for the plant. The type and depth of soil you have determines your plant selection, planning effort and watering regime.

San Antonio Soils

There are three types of soil in San Antonio: clay, clay loam and sandy loam.


Referred to locally as “gumbo,” heavy clay holds the most water, nutrients and organic matter but is extremely difficult to work. Never add sand to clay as it creates a lovely adobe, that is, brick. Use organic matter, expanded shale or biochar to increase “workability,” nutrient exchange and water infiltration.

Clay Loam

Clay loam is the predominant soil type in Bexar County and the Hill Country. However, it is often found in insufficient quantities to be desirable. Enrich your clay loam soil by adding organic matter, like compost.

Sandy Loam

Sandy loam is found predominantly in southern Bexar and associated counties. Sandy loam has great infiltration ability but limited water-holding capacity. Add organic matter or biochar to increase water-holding capacity.

Thin Soils of the Hill Country

Technically not a soil type, if you have excessively shallow soils that characterize the Texas Hill Country, carefully select plants that can thrive in shallow soils. Careful not to disturb the delicate native soil and leaf litter in any areas you plan on leaving natural. Opt for native plants that grow in thin soils. If soil amendments are necessary, however, compost can only benefit your plants.


Core Aerator: A core aerator is pushed across the grass and pulls little plugs of soil, making small holes to allow air, water and nutrients to penetrate the roots. This helps the roots grow deeply and produce a stronger, more vigorous lawn. It is not necessary with a healthy lawn, but may not hurt in heavy clay soils to alleviate soil compaction once every five years or so.


  • By ordinance, new lawns must have four inches of topsoil beneath the turf. We recommend at least six inches.
  • Native species, even large trees, will grow in as little as two inches of soil and fractured limestone.
  • Dig wide, shallow planting holes with sloping sides in predominantly clay and clay loam soils.
  • Minimize compaction, which is the curse of predominantly clay soils, with consistent applications of organic matter and occasional core aeration.