HOW TO GROW CACTI
In general cacti like warm or hot sunny southern exposures; they grow best in sandy, gravelly, or rocky loam or clay soils, according to the habits of the species; they succeed best with good drainage, a moderate or limited rainfall or a limited amount of moisture in the soil. They should have occasional dry periods to harmonize growth with their original desert habitats, and also all the summer heat possible. This produces the contracted growth characteristic of cacti with all their desert beauty and symmetry of colors and arrangement of spines, and their fine large showy flowers. Cacti do best in regions of limited rainfall and maximum sunshine, blazing-hot summers, and mild winters where the temperatures keep well above zero.
The bad effects of heavy rainfall can be overcome largely by including in the soil a large proportion of sand or gravel or cobblestones and by growing the plants on ridges or raised borders. The effects of fog and extreme humidity can be corrected somewhat by growing them in dry conservatories. Where the temperatures fall below the lowest temperatures given in the section on “How to Grow” for each species, cacti must be grown in warm greenhouses in winter and preferably throughout the year—with the exception of the hedgehog cacti, which rarely grow successfully in greenhouses. With the specific information given under the heading “How to Grow” for each species, it is possible to grow cacti successfully in the tropics and over a large part of the temperate zone. The important things are: warm sunshine, protection from too low temperatures, the right kind of soil, and limited watering or irrigation.