Soil texture is an important consideration when you start a garden, because texture determines the rate at which water drains through the soil. Clay soil can be problematic for gardeners because water does not readily pass through it and it is easily compacted, making it difficult for plant roots to take hold.
Soil texture is determined by the size of the mineral particles that make up the soil. Clay is made up of the finest particles, generally under 0.002 mm in diameter. Silt consists of particles from 0.002 to 0.05 mm and sand is made up of 0.05 to 2.0 mm particles.
Clay tends to form very hard clods when dry and becomes extremely plastic and sticky when wet. Soil that contains considerable amounts of clay but is not made entirely of clay is classified as sandy clay, silty clay, silty clay loam, clay loam or sandy clay loam, depending on its percentage of sand, silt and clay.
Soils that contain silt and clay retain moisture well and can be high in organic matter. This is good up to a point, but soils dominated by clay can be very hard to manage. Careful and fine tilling as well as the addition of organic material such as manure, green plant matter and sawdust can help to improve clay soil.