Soil is made up of many mineral particles mixed together with living and dead organic matter that incorporates air and water. Three basic factors contribute to the cannabis root’s ability to grow in a soil: texture, pH, and nutrient content.
Soil texture is governed by the size and physical makeup of the mineral particles. Proper texture is required for adequate root penetration, water, and oxygen retention and drainage as well as many other complex chemical processes.
Clay or adobe soil is made up of very small, flat mineral particles; when it gets wet, these minute particles pack tightly together, slowing or stopping root penetration and water drainage. Roots are unable to breathe because very little or no space is left for oxygen. Water has a very difficult time penetrating these tightly packed soils, and once it does penetrate, drainage is slow.
Sandy soils have much larger particles. They permit good aeration (supply of air or oxygen) and drainage. Frequent watering is necessary because water retention is very low. The soil’s water- and air-holding ability and root penetration are a function of texture.
Loam soil is ideal for growing cannabis. It Contains a mix of clay, silt, and sand. The different sized particles allow a large combination of pore spaces, so it drains well and still retains nutrients and moisture.
To check texture, pick up a handful of moist (not soggy) soil and gently squeeze it. It should barely stay together and have a kind of sponge effect when you slowly open your hand to release the pressure. Indoor soils that do not fulfill these requirements should be thrown out or amended.
U.S. cannabis seed bank offering regular seeds.