Growing San Pedro Cactus.

This section is directed at Trichocereus pachanoi (San Pedro) and Trichocereus peruvianus. The growth paramaters for these catus are the same. They are different than most columnar cacti in that they grow very rapidly, and enjoy a somewhat richer soil mix and more frequent waterings than most cacti. They are quite hardy, and will grow successfully in a wide range of conditions (I have seen very large, vigorous specimens growing unattended in the back of grass covered lawns, planted directly in the lawn soil, watered by the lawn's automatic sprinkler system). However, to achieve maximum growth rates their native environment should be imitated as closely as possible. The native habitat of these cacti is the western slopes of the Peruvian Andes, where the soil is very rich with humus and minerals, rainfall is not too scarce, and exposure to the sun and wind are at a maximum. I will describe ideal growth conditions (compiled from personal experience, books, and from the advice of someone who grows several dozen of them). However, I should begin by stating that these conditions also produce cacti with low mescaline content. The alkaloids in these cacti apparently are a defense mechanism against invading organisms, and increase during stressful conditions... particularly when the cacti are underwatered. This is a very gradual response... the mescaline content can take one or more growing seasons to increase after water starvation has commenced. Thus one strategy for raising these cactus is to purchase them at the desired size, and to "starve them out" for a full growing season before harvesting. If this is the strategy, the following "ideal growth conditions" should *NOT* be observed since they will contribute to decreases in potency!
For ideal growth, I have found the following variables to be important:
Lighting: One of the most important variables. Growth of these cacti occurs mainly during the brightest months of summer. In locations where intense, bright sunny days occur for only a few months, they will not grow rapidly. Growth can be greatly stimulated with high intensity plant growth lights such as used for marijuana cultivation, but year round operation of these 1000 watt bulbs can be very expensive. Also, as the cactus can be quite tall, care must be taken not to burn the tops of the plants. Ideally, angled lighting from both sides should be observed to allow full illumination along the entire column. When underwatering to increase potency, the cacti should be placed in a less exposed location, with partial shade. If the lighting is too bright for maximum potency increase (but not for maximum growth) the cacti will turn a lighter shade of green. This response occurs after only a few weeks, so adjust the lighting to achieve a darker shade of green.
Soil: The cacti should be planted in very porous soil. A typical cactus potting soil mix is OK, but can be improved by addition of extra pumice. The more porous the soil mix, the more frequently the cacti will have to be watered, and the less danger there will be of root rot and other problems of over-watering. However, the soil mix should also be fairly rich. I take 3 parts high pumice soil mix (much more pumice than in Hyponex cactus potting soil) and mix in one part forest compost. Additionally, I use a lot of plant fertilizer. Cactus are damaged by high nitrogen contents, so be sure to use a fertilizer with low nitrogen. Check the label... there are three digits (like 10-7-12) and the first is the nitrogen content. Use a plant food with the lowest ratio of this number to the other two. Special catus fertilizers are available... I use one called "Catus Juice" which has a 1-7-6 ratio, plus calcium which is a special factor for cactus. I feed my cactus at the recommended dilution about once a week. Don't begin this treatment immediately after repotting; let the roots set in. When attempting to increase potency, this feeding is not necessary since the cactus will not be receiving water.
Potting: These cacti like to send out far ranging lateral root systems near to the surface, so if potted they should be placed in very wide clay pots. Deep but narrow pots will result in stunted growth. Clay pots are required for proper drainage. Use of large clay pots is in many ways preferable to planting directly in the ground, since the watering, drainage, and feeding can be controlled more precisely. However, if attempting to increase potency, the cactus can be placed in small, constricted pots since good growth conditions are not desired. In any case, repotting cactus should not be idly done since it shocks the root system and injures the cactus. It is best to choose a suitable pot and stick with it.
Watering: When in full growth, the cactus should be watered quite frequently. The cactus should be watered when the subsurface soil is not damp to the touch. This will depend on many other factors. At one extreme, for a cactus in very well-drained, high pumice soil, potted in porous clay pots, receiving bright full sunlight all day long, in an exposed, windy, hot location, the cactus can be thoroughly watered every four days. If fed this frequently, the plant food concentration should be halved. One way to test soil dampness is to insert a small, clean redwood stake into the soil. If it comes out with small particles of sand clinging to it, the soil is still moist and should not be watered. During dormant winter months, the cactus should be watered much less frequently, perhaps once a month or so. This will stimulate root growth and result in faster growth during the hot season. As mentioned above, when attempting to increase potency, the cactus should not be watered at all for an entire growing season, and placed in a less exposed, partially shaded location.
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