Penis Cactus Care Guide 101

How to Grow and Care for a Penis Cactus

The penis cactus, or TBM for short, is the monstrose form of the Bolivian Torch Cactus, Trichocereus bridgesii. Its impressive branching and distinct look makes it a must-have for any cactus collector. But it’s not about the size of the cactus; it’s how you plant it.

In this blog we’re going to go over differences between the long and short forms of this cactus, as well as light, soil, and watering needs, general health and common problems, propagation, and more.

Varieties: Short Form vs Long Form

The penis cactus comes in two varieties, short form and long form clones. These "clones" refer to plants that have been propagated usually through cuttings to produce genetically identical offspring, ensuring new plants continue those desired traits.

Short form penis cactusLong form penis cactus

The distinctions between the two can be hard to observe as young plants but as they grow into mature cacti you’ll notice a few differences. The short form tends to branch off and form offsets quite a bit more, growing more compactly, whereas the long form produces less offsets and typically grows more vertically with elongated stems. The short form has about 2-3 inch sections while long form sections are about 4-8 inches and sometimes longer. Can you see the difference?

Optimal Lighting & Placement

The penis cactus wants bright light for at least 6 hours a day to maintain healthy thick growth. If you’re keeping this cactus indoors you will likely need a grow light so that you can avoid stretched out, etiolated growth.

How to Repot a Penis Cactus + Soil Tips

A good time to repot the penis cactus is when the plant has overgrown its container, it has become rootbound or top heavy, or simply for aesthetic purposes. This cactus needs a well-draining soil mixture that is a mix of about 70% inorganic material to 30% organic material, as this species tends to be more prone to overwatering.

Repotted penis cactus in well-draining soil

Consider gloves when handling this cactus to protect yourself from its spines. Gently remove your penis cactus from its previous container and break up the soil to give the roots freedom to grow out. Place it in the new pot and fill in the rest of the space with soil, firmly tucking it in for support. Make sure it feels secure and at a depth that’s not too deep but not too shallow. You can give it a little wiggle to test this. Mulching and top dressings can even add extra support and finish up an arrangement.

How & When to Water a Penis Cactus

Check to make sure that your penis cactus feels a bit deflated and softer to the touch rather than firm, freshly watered ones, and that the soil is completely dry before watering. When it’s ready, give your cactus a long full watering, making sure that any excess water is draining out of the bottom of the pot. Then you will wait for the soil to dry out completely again before watering.

Watering penis cactus

Water these plants regularly in the warmer Spring and Summer months. In the colder months, when it’s dormant, you should water it very infrequently—only when it looks very deflated, if at all, depending on your location. This will help avoid rot.

Maintaining Health: Common Issues and Solutions

A healthy penis cactus will have a bright vibrant green color, firm stems, and a smooth texture. Size, length, and shape will be irregular depending on the form, but a fully grown penis cactus will be about 2-3 feet tall with a similar diameter akin to a shrub. A few small, light brown blemishes might appear here and there on the skin but that is normal.

A common problem for this plant is fungal issues. Keep an eye out for circular, brown or black spots that can be a sign of these infections. Bridgesii in general are more prone to fungal issues so preventative treatment with a fungicide helps to keep it in good shape. Be on the lookout as well for dark splotches, splitting, and rotting for signs of overwatering.

Fungal spotsSplitting due to overwatering

Fungicides, well-draining soil, good airflow, and fertilizing in the growing season will help to keep your penis cactus happy and healthy. And a plant in good health is less prone to systemic issues forming in the long run.

Ideal Temperature, Humidity, and Climate

The penis cactus prefers a warm, dry climate. If you’re growing penis cactus outdoors, be sure to protect it from frost, as this can cause damage.

Keep your penis cactus in an area with good airflow. As we mentioned in the previous section, they are more prone to issues that arise from too much moisture.

Pest Control for Penis Cactus

The penis cactus is most commonly attacked by mealybugs, scale, and snails, and should be treated as soon as you spot them. Isopropyl alcohol and SlugGo are good treatment options, as well as keeping these plants free of weeds.

penis cactus with pest damage

How to Propagate a Penis Cactus

Propagating a penis cactus can be done through stem cuttings. Take a cutting from a healthy stem at the node, making sure to leave areoles on the mother plant so that new offsets can grow out. 

Taking a cutting of an offset
Allow the cut end to callus for a few weeks, and then place it in well-draining soil. As roots appear you may gradually introduce watering frequency.
Giving cuttings time to callus
planting penis cactus cutting in soil

Rare Flowers of the Penis Cactus

Flowers are actually extremely rare for the penis cactus. If it does bloom, it will bloom large white night-blooming flowers that are covered in white hairs on the outside. 


By following these care guidelines, you can nurture a thriving and impressive penis cactus in your own garden. This unique cactus not only adds an intriguing element to your plant collection but also serves as a great conversation starter. With consistent care and preventative treatment, you will set up your penis cactus for success and allow it to become a standout feature in your collection. 

Key Takeaways

  • The penis cactus, or TBM, is a monstrose form of the Bolivian Torch Cactus, Trichocereus bridgesii.
  • The short form (clone B) is more compact with frequent offsets, while the long form (clone A) grows more vertically with fewer offsets.
  • Needs well-draining soil with a mix of 70% inorganic and 30% organic material.
  • Water only when the cactus feels deflated and the soil is completely dry.
  • Healthy plants have vibrant green color, firm stems, and smooth texture.
  • Fungicides, well-draining soil, good airflow, and fertilizing in the growing season will help to keep your penis cactus happy and healthy.
  • Can be propagated through stem cuttings, but make sure to leave areoles on the original plant that the cuttings are being taken from.