By: Bonnie L. Grant, Certified Urban Agriculturist
Of all the varieties of cactus, Stenocereus is one of the broadest in terms of form. What is a Stenocereus cactus? It is a genus of typically columnar cacti whose branches develop in very unique manners. Stenocereus cactus plants are usually quite large and considered outdoor specimens when used in the landscape.
The world of cacti is a wondrous place filled with tiny to skyscraping plants in all shapes and colors. The many types of Stenocereus mostly fit the taller category, with vertical limbs that provide the main characteristic of the genera. Stenocereus cacti are native to the southwestern United States and northern parts of Mexico.
One of the more impressive and commonly known plants in this family is the organ pipe cactus, which can grow up to 16 feet (4 m.) tall. Other Stenocereus are more shrub-like and barely knee high.
A wide range of forms occurs in the genus but most have long limbs and branches. The name stems from the Greek word “stenos,” which means narrow. The reference refers to the ribs and stems of the plants. Most Stenocereus cactus plants are ribbed and have pronounced spines and range from gray to greenish gray and green.
The organ pipe cactus may be the most known of the genera but there are many spectacular specimens.
Stenocereus beneckei is a spineless form that has large creamy night blooming flowers. Stenocereus alamosensis is the octopus cactus, so named because of its numerous thick, long-spined stems that spring out almost horizontally from the base.
The genus has plants with extremely fun and descriptive names such as:
Such names give an insight into their various, wildly interesting forms. Most develop ribbed, long stems with almost sinuous beauty. After the rainy season, large brightly colored to white flowers are produced followed by spiny fruit.
Stenocereus cacti hail from arid regions. They prefer desert conditions and have a minimal tolerance to cold temperatures. The desert has a definite rainy season in which the cacti achieve most of their growth and store moisture in their limbs.
The spines on most species help prevent excess evaporation and protect them from some pests. In the home landscape, they will need supplemental watering only in the hottest periods.
Gritty, rocky or sandy soil provides the best environment for their roots. They do not need pruning and need minimal nutrition. In warm regions, they are drought tolerant and welcome plants with few needs, but a powerful presence in the landscape.
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Stenocereus (Gk. stenos, narrow, L. cereus, candle) is a genus of columnar or tree-like cacti from the Baja California Peninsula and other parts of Mexico, Arizona in the United States, Colombia, Costa Rica, Guatemala, Venezuela and the ABC islands of the Dutch Caribbean. The genus has been enlarged by the addition of species from several other genera. A close relative is the peculiar chinoa or chende cactus, Polaskia chende.
The flowers are mostly borne near the apex of the stems and mostly nocturnal. They are considered easy to grow and generally grow slowly.
Stenocereus thurberi (the organ pipe cactus) is a well-known member of this genus and is widely distributed in Arizona and northern Mexico.
The fruit is similar to a dragon fruit. Those of Stenocereus gummosus, acidic and very refreshing, are highly favored by the Seris of northwestern Mexico  who call the cactus ziix is ccapxl  - "thing whose fruit is sour". It is commonly known in Spanish as pitaya agria, or by the English translation Sour Pitaya. S. griseus (Dagger Cactus) fruits, locally known as iguaraya, are relished by the Wayuu from the La Guajira Peninsula of Colombia. 
Stenocereus are often used as ornamental plants in hot and arid regions, and as noted above, some species can double as a fruit crop.
The interior of Stenocereus trunks often grows to form tough, cane-like stakes suitable for certain kinds of construction. The Wayuu use those of Dagger Cactus for building wattle and daub walls, a technique they call yotojoro, after their name for the cactus wood "canes". 
Observing your cactus is very important. When you observe your plant, you can find any potential issue becomes they become a problem and solve it immediately.
The living conditions of cacti vary differently from one species to another. There are cacti that grow well in dry sandy soils, there are others that do well in rainforests, and so on.
This is why there is no potting mix that suits every cactus. When you decide to plant a cactus, do simple research about the species and its living conditions.
After that, get a potting mix that is as similar as possible to the cactus’ natural living conditions.
Like any other plants, cacti need watering. The question, how frequently should you water a cactus? Just as the potting mix, there is no single solution to this. One thing is certain: a watering schedule is necessary.
Most types of cactus grow during the warmer seasons. At this time, they need to be watered adequately. During cold seasons, however, they don’t need as much watering, if any.
On average, during spring or summer, you can water a cactus on weekly basis or more, depending on whether the soil has dried or not.
The watering requirements also depend on the placement of the cactus. A cactus that is placed under direct sunlight will need more watering compared to one that is placed under a shade.
Both overwatering and underwatering must always be avoided. The former makes the roots of the cactus rot while the latter makes the cactus pale and bends. You want neither of these.
Balance is very important here.
Nutrients are necessary for a plant to grow healthy and well. This, of course, applies to cacti as well. Fortunately, fertilizers designed for cacti are widely available.
For most cactus plants, the growing season is in the warmer months. It is at this time that fertilizer is necessary.
When looking for fertilizer, make sure to get one that has high phosphorus but low nitrogen contents. This kind of fertilizer will help to maintain the cactus’ healthy look.
If you potted or repotted a cactus recently, don’t use fertilizer until it has established itself in the new pot. This process can take as long as two months.
Next is sunlight. This, again, varies depending on the types of cactus. For example, desert cacti like direct sunlight. The tropical cacti, on the other hand, prefer partial shade.
What about indoor cacti? To ensure they get enough light, place them about 4 feet from a window facing south or east. Rotate the cactus every month or so. Too much sunlight will turn them white or yellow.
What if you can’t provide enough sunlight for a cactus? In that case, you can use grow lights as substitutes.
When it comes to pests, cacti don’t need as much case as other plants. Pests are seldom a problem for cacti, after all. That being said, once in a while, they might cause a problem.
To manage pests, practice measures to prevent pests. For example, keep the cactus as healthy as possible. That means ensuring the plant gets enough sunlight, water, and has proper drainage.
If a cactus thrives, it is less likely to suffer from pest attacks. Also, keep the pots clean from any dead leaves which might attract pests.
In case you find any pests on your cactus, you can use insecticidal soap to get rid of them. Do keep in mind that the soap can damage cacti. So, be sure that the soap is safe to use for cacti before applying.
When you notice that your cactus’ roots grow outside the pot, it is time to repot the plant. It is recommended to repot a cactus once every 2 to 4 years.
When you repot a cactus, make sure to use the necessary tools to ensure both your and your plant’s safety.