The “dildo cactus” is a common name for Stetsonia coryne, a columnar cactus recognized for its distinctive shape and prominent spines. It is a legitimate species within the Cactaceae family.
Understanding the Dildo Cactus
Stetsonia coryne, also known as the “toothpick cactus,” is a tall, tree-like columnar cactus native to arid and semi-arid regions of South America, including Argentina, Bolivia, and Paraguay. It develops a thick, short trunk from which numerous erect or arching branches emerge, creating a broad, multi-branched form in its natural habitat. This cactus can reach impressive heights of 15 to 30 feet in the wild.
The stems are typically bluish-green when young, maturing to an olive or greenish-gray hue. They feature 8 to 9 blunt, somewhat notched ribs running vertically along their length. A defining characteristic is its formidable spines, which are straight, stiff, and sharp, often appearing yellowish to black and eventually turning white with dark tips. These spines can be quite long, with central spines reaching 2 to 8 cm and radial spines up to 3 cm. Mature plants may produce large, white, funnel-shaped flowers that open at night, though this is less common in indoor cultivation.
Cultivating Dildo Cactus
Light Needs
Stetsonia coryne thrives in bright, direct sunlight, requiring a minimum of six hours daily for optimal growth. Indoors, a south-facing window is ideal for ample light. If natural light is insufficient, supplementing with a grow light supports healthy development.
Acclimate the cactus gradually to intense direct light, especially if it has been in lower light conditions, to prevent sunburn. Sunburn appears as discolored or scorched patches. Placing it outdoors for the summer can be beneficial, but introduce it to full sun incrementally.
Potting Medium
Growing Stetsonia coryne requires a well-draining potting medium. This cactus naturally grows in rocky or sandy soils and is highly susceptible to root rot if moisture lingers. A specialized cactus and succulent mix is recommended, as these formulations offer necessary drainage and aeration.
For a homemade alternative, a blend of equal parts potting soil, coarse sand, and perlite or pumice creates an excellent substrate. Adequate drainage holes are essential to allow excess water to escape freely.
Watering Frequency
Water Stetsonia coryne using the “soak and dry” method: water thoroughly until it drains from the pot’s bottom, then allow the soil to dry completely before the next watering. Overwatering is a common issue that leads to root rot, to which this cactus is particularly prone.
During the active growing season (spring and summer), water every 2-3 weeks, or when the soil is entirely dry. In autumn, reduce watering significantly, and during the winter dormancy period, cease watering almost entirely to prevent rot, keeping the plant cool and dry. Adjustments may be necessary based on environmental conditions like temperature and humidity, as warmer, drier conditions will necessitate more frequent watering.
Ideal Environment
Stetsonia coryne prefers warm temperatures, ideally 75-90°F (25-32°C) during its active growing season. It can tolerate higher temperatures up to 95°F (35°C) if monitored. During winter, while adult plants can tolerate brief periods as low as 28.4°F (-2°C), it is generally safer to protect them from frost, especially younger specimens.
This cactus thrives in low humidity, typically 30-50%, reflecting its arid native habitat. It adapts well to dry indoor conditions. If growing outdoors in regions with cold winters, bring the plant indoors to a cool, dry location to induce dormancy and protect from freezing temperatures.
Feeding Your Cactus
Fertilization for Stetsonia coryne is generally not a frequent requirement, especially if the potting mix is fresh. If desired, a balanced cactus fertilizer can be applied sparingly during the active growing season (spring and summer). Diluting to half strength is recommended to prevent nutrient burn.
Avoid fertilizing during the plant’s dormant period in fall and winter. Over-fertilization can lead to a buildup of salts, which can harm the plant. Repotting every few years into fresh soil can replenish nutrients without constant feeding.
Multiplying Your Dildo Cactus
Propagating Stetsonia coryne is most commonly achieved through stem cuttings. To take a cutting, select a healthy, mature stem segment and make a clean cut using a sharp, sterile knife.
After taking the cutting, allow the cut end to dry and form a callus before planting. This callusing process prevents rot and can take anywhere from a few days to several weeks, depending on the cutting size and environmental humidity. Once callused, plant the cutting in a well-draining cactus mix. While seed propagation is also possible, it is a much slower process.
Troubleshooting Common Problems
Stetsonia coryne is generally resistant to many common plant issues but is particularly sensitive to improper watering. Overwatering is the most frequent cause of root rot, which can manifest as softening stems or a mushy base. If rot is detected, it may be necessary to unpot the plant, trim affected areas, and allow it to dry thoroughly before repotting in fresh, dry soil.
Conversely, underwatering can cause the cactus to shrivel or appear deflated, indicating a need for a thorough drink. Common pests that may affect Stetsonia coryne include spider mites, mealybugs, and scale insects. Regularly inspecting the plant for these pests and treating them with insecticidal soap or neem oil can help manage infestations. Yellowing stems can sometimes indicate nutrient deficiencies or overwatering.
Handling Your Dildo Cactus Safely
When handling Stetsonia coryne, exercising caution is important due to its prominent and sharp spines. Wearing thick, protective gardening gloves is recommended to prevent painful punctures. Tongs or a folded newspaper can also be used to grasp the cactus stems during repotting or relocation, minimizing direct contact with the spines.
While the plant contains some alkaloids, it is generally considered benign to humans and pets in a typical home environment. However, the physical injury from spines remains the primary concern. Keep this plant out of reach of small children and curious pets to avoid accidental contact.