Echinopsis pachanoi
The San Pedro cactus is very easy to grow in most areas. Because it grows naturally in the Peruvian Andes Mountains at high altitude and with high rainfall, it can withstand temperatures far below that of many other cacti. It requires fertile, free-draining soil. They average half a meter per year of new growth. They are susceptible to fungal diseases if over-watered, but are not nearly as sensitive as many other cacti, especially in warm weather. They can be sunburned and display a yellowing chlorotic reaction to overexposure to sunlight.
Cactus
Many smaller cacti have globe-shaped stems, combining the highest possible volume for water storage, with the lowest possible surface area for water loss from transpiration. The tallest free-standing cactus is "Pachycereus pringlei", with a maximum recorded height of , and the smallest is "Blossfeldia liliputiana", only about in diameter at maturity. A fully grown saguaro ("Carnegiea gigantea") is said to be able to absorb as much as of water during a rainstorm. A few species differ significantly in appearance from most of the family. At least superficially, plants of the genus "Pereskia" resemble other trees and shrubs growing around them. They have persistent leaves, and when older, bark-covered stems. Their areoles identify them as cacti, and in spite of their appearance, they, too, have many adaptations for water conservation. "Pereskia" is considered close to the ancestral species from which all cacti evolved. In tropical regions, other cacti grow as forest climbers and epiphytes (plants that grow on trees). Their stems are typically flattened, almost leaf-like in appearance, with fewer or even no spines, such as the well-known Christmas cactus or Thanksgiving cactus (in the genus "Schlumbergera").