About 5 years ago, Sheridan Cleland of MyPDFscripts wrote the below article on his blog. Soon after, the site disappeared. I wanted to keep the memory alive, because these practices by the studios have not changed. They have only become worse.
Cacti are one of my favorite types of plants to grow inside all year and outside in summer. Unfortunately, the ambient air tends to stay moist during most seasons, a condition which makes cacti unhappy. Cactus potting soil can enhance drainage, increase evaporation and provide the dry conditions that cacti favor.
christmas cactus need rich well drained soil so be sure that the container chosen for your plant has drainage holes punched through the bottom of the pot some experts recommend adding leaf mold or compost to the container but garden compost carries unwanted pests along with desired nutrients