Marin County Soil Data
Marin County, California
USDA SSURGO / PHZMAvg pH
5.9
Texture
Loam
Drainage
N/A
Organic Matter
3.5%
Hydrologic Group
N/A
Data Story
About Soil in Marin County, California
Acidic Coastal Soils in Marin
Marin County has an average pH of 5.91, making it significantly more acidic than the national median of 6.5. This score is also lower than the California average of 6.34. The county’s soil score of 46.1 sits just below the state average of 48.6.
Sandy Loam Characteristics for Drainage
The soil composition is 43.1% sand, 32.4% silt, and 22.2% clay. This mix provides excellent aeration and workability for gardeners. The high sand content helps water move through the profile, though it may require more frequent nutrient monitoring.
Rich Organic Matter Near the Coast
Marin boasts an organic matter content of 3.46%, which is higher than the California average of 3.30%. However, the available water capacity of 0.132 in/in is slightly lower than the state benchmark of 0.141. This rich organic content supports healthy microbial life and plant growth.
Inferred Drainage for Coastal Hills
Specific drainage class and hydrologic group data are not available for Marin. The high sand percentage of 43.1% suggests naturally good drainage in many areas. Homeowners should still watch for erosion on the county's famous steep slopes.
Coastal Classics in Zone 10a
USDA Hardiness Zone 10a allows for a long growing season with very little frost. Cool-weather crops like kale, artichokes, and berries thrive in this misty, coastal climate. Start your cool-season garden now to take advantage of the mild temperatures.
Soil Composition
Soil pH
Soil Series
Detailed soil series data not yet available for this county.
Hydrologic Group
Hydrologic group data not available.
Drainage Class
Drainage class data not available.
Soil Profile
Dominant texture: Loam
Typical soil profile. Actual depths vary by location.
USDA Soil Orders
Acidic Soil Detected
Your county's average pH is 5.9. These products help balance soil pH for healthier grass.
Browse Soil AmendmentsFrequently Asked Questions
What type of soil does Marin County have?
Marin County's soil is classified as Loam. This indicates the relative proportions of sand, silt, and clay — 43% sand, 32% silt, and 22% clay. Loamy soils hold moisture well and support a wide range of plants.
Is Marin County's soil acidic or alkaline?
Marin County's soil has a pH of 5.9, which is moderately acidic. This range suits many crops and is common across much of the eastern US.
What is the drainage class for Marin County?
Drainage class data is not currently available for Marin County.
What crops or plants grow well in Marin County's soil?
Based on Marin County's Loam texture, pH of 5.9, and drainage class, the soil is well suited for vegetables, grains, and most field crops, row crops and vegetable gardens.
What USDA soil order is found in Marin County?
The dominant USDA soil order for Marin County is not currently available in our dataset.
Soil & Planting Advisory: Marin County
Soil Verdict
Marin County is in USDA hardiness zone 10a, a very warm climate zone. where winter lows can reach 30°F. Warm winters keep soil biology active nearly year-round, accelerating decomposition but increasing pest and disease pressure in topsoil.
Planting Guidance
Tropical and subtropical plants are viable. Year-round gardening is possible, though summer heat may limit some cool-season crops. Frost is rare; tender plants can overwinter with minimal protection. Always match plant selections to the specific microclimate of your property — low spots, slopes, and wind exposure can shift effective hardiness by half a zone.
Soil Implications
Rapid organic matter turnover means soils can become nutrient-poor quickly; test annually and fertilize based on results. High soil temperatures favor certain soilborne pathogens; practice crop rotation and avoid overwatering.
Regional Context
Marin County is somewhat warmer than the California statewide average. The zone range of 9b-10a within the county means soil and planting decisions should account for local elevation and topography.
Planning your lawn? View lawn care data for Marin County on LawnByCounty.com →
Other Counties in California
Soil data sourced from USDA SSURGO via Soil Data Access. Data is informational only and should not be used as a substitute for on-site soil testing. Contact your local NRCS office for site-specific soil information.