Caring For Your San Pedro Cactus

The following information also generally applies to other Trichocereus species, Ariocarpus, Astrophytum, Saguaro and other North American cacti.  (See soil mix recipe for additional note.)

     Soil:

San Pedro cacti (Trichocereus pachanoi, recently re-classified as Echinopsis pachanoi) thrive in moderate to rich soil that provides good drainage.  Avoid heavily compacting soils.  Pre-mixed potting soil, with no added fertilizers, is available at any garden center and can be used alone or can form the basis of a good custom blend as in the recipe below. Commercial cactus mixes which are available at nurseries and stores such as Home Depot are even better as they are usually prepared using a combination of sand, organic matter, and larger particulates such as small stones, perlite, or vermiculite.  These insure that drainage and aeration of soil will be adequate.  One benefit of using these pre-packaged source materials is that they tend to be relatively clean and not in need of sterilization.    

Here is a simple recipe, using ingredients which are easily purchased, that can be a good basis for anyone who wishes to grow a few, or a lot of plants. 

6 parts potting soil (or your own local, preferably rich, soil)

2 parts sand

3 parts vermiculite or perlite or (preferably) a mix of both

1 part composted steer manure  (For Ariocarpus, Astrophytum, Saguaro and other slower growing North American Cacti, exclude composted steer manure or reduce to ¼ part.)

The steer manure is optional and may be omitted or substituted with other organic fertilizer.  Earthworm castings are superior to steer manure as a growth stimulant and are the preferred choice.  ¼ part bat guano is an excellent addition if available. Vermiculite and perlite increase the aeration of the mix, promoting fast and prolific root growth.  Kelp meal and alfalfa meal may be added in 1/2 to 1 part proportions and benefits the growth of new roots and shoots.

     Planting:

Starting from cuttings:  If you are starting with cuttings, make sure the cut end has dried to form a callous.  This usually takes one week from the time of cutting.  Slices that are 4 to 6 inches long may be used to start a new plant.  Plant the calloused end into soil just deep enough to hold the piece upright.  Alternatively, cuttings can also be laid on their side and partially immersed in soil.  These horizontal plantings will eventual produce roots and upright offshoots.  Cuttings can start rooting within two or three weeks under optimum temperatures.  Once established, they tend to start putting off new growth fairly quickly. 

Starting from rooted plants:  If you are starting with a plant that you’ve acquired bare-root, simply place the new plant in an appropriate size pot (or outdoors in rich garden soil if you live in a no-freeze zone) and arrange the roots comfortably as you fill the new pot with soil.  Try not to bury the stem much farther than where the old soil line is- as is noted by where the green starts.  Water well so that the soil settles and supports the plant. A topping of a quarter inch to one inch layer of small pebbles or gravel can provide additional support, conserve moisture, and be pleasing to the eye.

     Watering:

Trichocereus is a fast growing South American genus that can tolerate and process more water than do most North American desert varieties.  Nevertheless, the basic rule is don’t water when still moist but water thoroughly when dry.  This will vary according to season and climate.  In summer, the above mentioned soil mix might easily dry once or twice a week depending on the size of potting container used.  A well draining soil mix may be watered more frequently than soil that is heavy and compact or which has a clay-like consistency.   During winter, slow watering down (unless you are growing indoors) to once a month.  These plants can survive for a year or more without a drop of water.

      Light:

Trichocereus can tolerate substantial direct sun but will slow its growth or burn if it receives too much light in a hot climate.  Growers in hot desert areas find morning sun and afternoon shade, or the use of shadecloth, to accelerate robust growth.  Milder or northern climates may not require much, or any, sunburn protection.  Symptoms of insufficient light are spindly and narrow growth from new shoots.  Symptoms of sunburn are yellowing of skin and little or no new, green growth at the growing tip. 

     Temperature:

Many cacti are not winter hardy (including Trichocereus species) and will need to be protected from freezing weather.  Growing in containers that can be moved indoors is recommended in northern climates.

Trichocereus grows fastest when days are warm and nights are not too chilly.  Only a very mild and brief frost can be tolerated before freeze damage occurs, usually the growing tip is affected first and will appear to darken.  This damage will eventually spread downward to the rest of the plant.  Should this occur, you can cut the damaged tip off, move the remaining plant to a warmer area, and it will re-grow a new tip(s) when temperatures return to the normal growing range. 

     Fertilization:

In summer, long days and high temperatures can produce quick growth.  At this time a good liquid fertilizer can be used once a month.  During winter no fertilizer is needed and may make the plant somewhat more susceptible to frost damage.