How to Grow a San Pedro Cactus Indoors

Locate a 5- to 6-inch diameter plant pot ensuring that is has at least three to four holes in the bottom for water drainage. Fill the inside of it with a 1/4- to 1/2-inch layer of gravel to assist with drainage.

Fill the pot with a cactus potting mix, until it is half full. Cactus mix is available at any garden center or plant supplier. Water the mix until it is damp but not soggy and holds together when you squeeze it in your hand.

Put on garden gloves and carefully remove the San Pedro cactus from the nursery pot. Place the roots into the new pot and add additional soil mixture until it reaches the base of the cactus. Do not apply soil above the green portion. Water the soil again to moisten the upper layers.

Place the pot in an area with direct sunlight, such as a windowsill.

Water the soil in the pot once per week by filling a sink with 2 inches of water and placing the pot into it. Allow the top of the soil to dry completely in between watering. Stop watering in the late fall when the cactus goes dormant and resume again in the early spring.

Apply a liquid cactus fertilizer to the soil in the pot, choosing one that has numbers of 4-7-7 or 2-7-7. The numbers indicate the percentages of nitrogen, phosphorus and potassium in the product. Apply the fertilizer only at the suggested intervals on the package, since too much will cause them to deteriorate.

Move the pot to a cooler location in winter, such as a basement or even a shed. The optimal winter temperatures for a San Pedro cactus is between 40 and 50 degrees Fahrenheit, although it can survive indoors at room temperature as well.