Soil types in California

What this means

What California soils mean for gardens, lawns and septic systems

For gardens

Typical topsoil in California is neutral: pH 6.7 (most land between 5.8 and 8.2), the range most vegetables, flowers and lawn grasses prefer.

Loamy topsoil (loam, silt loam and similar) covers 57% of the land: generally the easiest soil to garden, holding moisture without staying waterlogged. The most common surface texture is loam (10% of the land).

81% of the land is moderately well to excessively drained, which suits most garden plants.

For lawns and yards

On 54% of the land, rain soaks in slowly (hydrologic groups C and D, including dual groups that are D until drained). Expect runoff and puddles after heavy rain: core-aerate compacted lawns and keep ground sloping away from foundations.

For septic systems

For conventional septic absorption fields, NRCS rates 79% of the land in California very limited, 4% somewhat limited and 4% not limited (13% not rated, such as urban land, pits or water).

Where the soil is very limited (slow permeability, a high water table, flooding, shallow bedrock or steep slopes), alternative systems such as mound or sand-filter designs are common and cost more.

Flooding is mapped on 11% of the land (2% occasional, 1% frequent).

Only a licensed site evaluation or perc test at the actual lot decides whether a system is allowed and which design.

Generated from the mapped numbers above using fixed rules, not a site visit. See how these notes are written.