This is a photo of my San Pedro cactus I had when I lived in Arizona. This is hard to grow it is extremely sensitive to too much water and too much sun. Soil should be 95% sand so it is very well drained. It does ok with a few hours of cool temperature early morning sun but needs full shade from 11 am until dark every day. If your cactus turns yellow it is getting too much sun. If your cactus turns black and rots cut it off it will spread like cancer.
First year I tried to grow this it kept rotting off and I kept cutting it down and cutting of the black rot. Let the cuts dry a week in the warm weather shade before planting. This cactus is slow to root it takes a month. It roots best laying on its side. It will grow 1 or 2 or 3 new plants from a short 8" long cutting. Plant your cutting just below the soil surface in about 2 months you will begin to see tiny little cactus bugs poking their way up through the soil. Once it starts to grow it grows faster. It is ok to water it a little if you live where it does not rain but be very stingy with the water no more than a tablespoon of water each time. Do not water again until soil is 100% dry. It grows at a med speed compared to other cactus about 1 inch per month. It is much slower to root in pots but does very well in pots especially if you live where you get lots of rain. Keep the plants out of the rain. We had no rain for 11 months in AZ then we had a big rain all my cactus rotted off and fell over. I cut off all the rot and replanted. It took me about 2 years to learn how to grow this cactus. Once it gets growing and gets some good roots deep in the soil then it grows much faster 2 feet per year. Once a year it makes very nice white flowers that last about 1 week. A small 12" plant might make 1 or 2 flowers but a 6 foot tall plant will make 20 beautiful flowers. Once the plant gets about 5 feet tall it starts to grow more plants up from the soil around the base of the mother plant. Within 3 years you can have 5 to 7 tall plants and within 10 years it can be a giant with 200 arms and 1000s of flowers. These are not native to AZ or the USA but there are several giant plants in neighbor hoods all over AZ. I should have taken some photos of the 15 foot tall cactus where I got my cuttings in Tempe AZ . You can buy cuttings on ebay. Sorry this is not a very good picture this is my first year attempt to grow this cactus. Plants look much nicer growing the cutting horizontal so you can not see the cutting all you see is the new cactus growing up from the soil.