The San Pedro cactus is arguably the most popular columnar cactus in desert gardening circles, Trichocereus pachanoi [try-koh-KER-ee-us puh-KAH-no-ee] gets its name from the hairy (tricho) floral tube.
This Trichocereus (Echinopsis) It hails from the South American countries of Argentina, Bolivia, Chile, Ecuador, and Peru.
In 1974, H. Friedrich and G. D. Rowley merged the genera Trichocereus and Echinopsis (ek-in-OP-sis, referring to a similar appearance to sea urchins).
While the genus Echinopsis pachanoi is currently valid, there’s a push to restore Trichocereus as the sole genus due to irreconcilable differences in the genera.
The plant was cataloged by the American botanist J. N. Rose who named the species after Ecuadorian professor Abelardo Pachano.
As a result of its popularity, the cactus (most commonly known as San Pedro) has 25 different common names in Spanish alone.
A few examples are andachuma, gigantón, huachuma, and wachuma.
Various Trichocereus species are scattered throughout the Andes mountains, with San Pedro being native to altitudes of 6,600′ to 9,800’ feet.
There are a total of five pachanoi species.
It should also be noted a close relative, the Peruvian torch cactus (Trichocereus peruvianus) is so similar the two species are almost synonymous.
San Pedro Cactus Care
Size & Growth
The San Pedro cactus is a fast-growing, multi-stemmed plant growing to measure approximately 5.9’ feet wide and up to 19.7’ feet tall.
Individual stems range from 2.4″ to 5.9” inches thick and may have between 4 and 8 ribs each.
Given the right amount of moisture, sun, and soil, these cacti are able to grow up to 1’ foot per year.
The stems range from pale green to blue-green, darkening with age.
Flowering and Fragrance
San Pedro buds are pointed and produce a fluted whitish flower in July.
They bloom at night and remain open, with the fragrant flowers measuring approximately 8.7” inches in diameter.
Black or brown hairs and scales cover the fruit, which measures 1.9″ to 2.4” inches long and 1.2″ inches in diameter.
Light & Temperature
San Pedro thrives in full sun after the first year, although seedlings may suffer sunburn in direct sunlight.
Be sure to gradually introduce a plant overwintered indoors to direct light, as they may get sunburned if transferred directly.
A healthy San Pedro can withstand temperatures are low as 50° degrees Fahrenheit (10° C) with the occasional brief dip as low as 15.8° degrees Fahrenheit (-9° C).
This resistance to cold may be bolstered through the use of Valerian flower extract.
It can thrive in USDA hardiness zones 8B to 10B.
Watering and Feeding
As with many succulents, this cactus will go dormant in colder months and should be given no water between October and April to reduce the risk of rot setting in.
Seedlings may have a very diluted mix of fertilizer occasionally, but adults are capable of being fed an undiluted concentration.
Soil & Transplanting
Trichocereus pachanoi requires fertile, slightly acidic soil with good drainage.
A minimum amount of humus works best to reduce the risk of rot.
Seedlings will benefit from a tiny amount of highly diluted fertilizer, although adults can handle larger quantities.
Seedlings may be safely transplanted to pots after one year.
Grooming and Maintenance
Trichocereus pachanoi may be clipped for grafting or pupping.
Be sure to clip 12” inches or more, as larger plants grow faster.
No other grooming is necessary for a healthy plant.
The cactus is also low-maintenance.
Be sure the soil is well-drained.
A bit of sulfur or diatomaceous earth added to the soil works well as a natural pesticide.
How To Propagate Trichocereus Pachanoi
San Pedro seeds are very small and easy to propagate using the Fleischer technique.
You will need the following items:
- Clear glass jars (such as mason jars or salad containers) with lids
- A mix of fine sand and sowing soil (potting soil increases the risk of rot)
- A spray bottle
- Seeds verified less than ten years old (within one year are the most viable)
Sowing The Seed
- Fill the bottom of the container with the soil mix.
- Level the soil and tamp down gently to provide a stable platform for the seeds.
- Sprinkle the seeds onto the soil, allowing them to rest on top.
- Lightly mist the soil with water and cover.
- Place the containers in a sunny area where they won’t suffer direct exposure to sunlight.
- You may also use an LED lamp of 150 watts or higher. More on growing under artifical light.
- Ambient temperature should remain between 77° and 86° degrees Fahrenheit (25° – 30° C).
- Seeds should germinate within 2 to 3 weeks.
- A seed that fails to germinate in 6 weeks or shows signs of white mold on the seed itself is likely dead.
- Open the lid and dry the soil out before starting again.
You should also open the lid to dry if you see signs of fungus gnats.
Signs of mold in the jar should be rinsed away with the spray bottle, and the jar allowed to dry out before reclosing.
Be warned; the market is saturated with poor quality seeds.
Be sure to check the age of the seed when planning to self-germinate.
The younger they are, the better the chances of successful germination.
Trichocereus Pachanoi Pest or Disease Problems
All Trichocereus species are susceptible to deadly fungal infections.
These include damping off, orange rot, and witches broom disease.
Black rot is generally harmless and will heal itself after a short time.
Root mealybugs, scale, and spider mite may also be a problem.
Scale is easily scrubbed off when caught early.
Suggested San Pedro Cactus Uses
As with many succulents in the Cactaceae family (and throughout the Andes and Amazon basin in general), the San Pedro cactus has long been valued by natives for medicinal and religious purposes.
In the US, it has become a viable substitute for peyote during hallucinogenic rituals due to the presence of mescaline.
This cactus is highly ornamental and works great in any desert-themed garden setting, as well as an indoor decorative plant.