San Pedro

The San Pedro or Achuma cactus has been, and still is, one of the most important sacred plants amongst many Native South- American tribes. The use of San Pedro originated in the northern parts of the Andes, from where it quickly spread troughout South America. The natural range of the San Pedro is on slopes in mountainous areas, where it lives in very sunny and well drained conditions. Learning about your cactus’s needs and imitating it’s natural habitat will improve the health of your plant and increase your succes in growing.

Growth habit:
San Pedro or Achuma are a number of species from a genus of cactus, called Trichocereus. They have large columnar bodies and a large rootball that anchors them on the rocky sloping terrains they grow on. In nature they usually grow in a single column untill they fall over. After they’ve fallen over, they sprout new shoots from the sidebuds, resulting in small groups of columns.

Soil:
San Pedro’s and Achuma’s grow in a very wide variety of soils, and are definitely not picky. They’ll thrive in a standard cactus soil with some extra perlite added to it. Drainage is the most important quality your soil should have, allowing water to drain freely and enough air to reach the roots.

Watering and fertilisation:
Watering cacti is quite simple, only water them when the soil has almost completely dried out from the previous watering. Give less water when the weather outside is cold and rainy, or nothing at all in winter. There’s more harm to be done by giving them too much water than too little. An easy way to check if the soil has dried out, is sticking a clean toothpick in the soil. If the toothpick comes out clean with just a little dust on it, the soil is completly dry. If there are still soil particles sticking to the toothpick, it doesn’t need water yet. Be sure to check the bottom layer of soil, not just the upper part, which can be dry while there’s still enough moisture below.
As for fertilizing your san pedro’s, this is not neccesary, if you do, it’s best done by giving them a diluted standard cactus fertilizer.
 
Light and temperature:
These have the most influence on the growth form of your cactus; when there’s not enough light, the temperature should be low as well. Having your cactus too warm with not enough light, will make it stretch toward the light and makes it more succeptible to disease and pests. Give your cacti as much light as possible, but introduce them slowly in high light conditions to prevent sunburns. Especially the true San Pedro (Trichocereus pachanoi) is quite sensitive to sunburn when first introduced to a new environment.
This means that when you buy or repot a plant, or when taking them outside after overwintering indoors, you should keep it in dry shade for a few weeks to let it adjust to it’s new environment. Expose it gradually to full sun over a period of a month. During summer, San Pedro’s that are in a greenhouse or outside under raincover do better with a bit of shade from the mid-day sun.