The scientific name of the San Pedro cactus is Echinopsis pachanoi. You are likely to see this plant retailed as Trichocereus pachanoi or Cereus pachanoi. San Pedro is a multi-stemmed columnar variety of cactus that can grow as tall as 20 feet with a spread of 6 feet or more. This undemanding plant is frost-tolerant only in USDA Zones 8b through 10 and hardy to 15 degrees F. Healthy, mature specimens produce showy, fragrant, white night-blooming flowers in early July.
Create a potting mix for your San Pedro cactus by combining 2 parts each loam or potting soil, coarse sand and peat moss with 1 part fine gravel. Plant the cactus in a clay pot at the same depth that it occupied in the growing container. Clay is the best material for growing cacti since it provides better drainage than other types of containers do.
Set the plant in the sink and water it slowly and thoroughly until you see liquid draining from the holes in the pot. Allow it to drain completely. Check the drip tray 24 hours later for the presence of residual draining water and empty it. The pot shouldn't be allowed to rest in water. Don't water again until the soil is completely dry.
Place your cactus in the sunniest spot in your home. If sunlight isn't available, keep it in the best-lit spot you can provide. Outdoor specimens that have been nursery-grown typically perform best when situated where they'll receive about 25 percent shade each day. Try to replicate the lighting conditions that this cactus was grown with if you keep it outside. If it wasn't raised in full direct sun, then don't expect it to thrive in brutal heat without some shade.
Keep your San Pedro cactus warm. This native of Peru and Ecuador likes heat and performs best at sustained temperatures well above 50 degrees F throughout the growing season.
Feed your San Pedro cactus an all-purpose cactus fertilizer monthly during the growing season. Follow the package instructions carefully.
Move the plant to a cooler location during the winter months, if possible. Optimum winter nighttime temperature is 48 degrees F. Continue to provide as much bright light as possible during the daytime hours.