The Blue Candle Cactus (Myrtillocactus geometrizans) is a distinctive columnar cactus known for its unique blue-green stems and architectural form. Native to central and northern Mexico, it develops a candelabra-like branching habit as it matures, making it a visually striking addition. Understanding its growth patterns is important for successful cultivation.
Understanding Blue Candle Cactus Growth Rate
The Blue Candle Cactus has a moderate to fast growth rate compared to many other cacti. While it can exhibit rapid growth in its natural habitat, its rate varies significantly when cultivated in pots, often appearing slower. Under ideal conditions, this cactus can grow several inches per year, with growth often accelerating with age. New growth typically appears thicker and more robust when care conditions are met.
Key Factors Influencing Growth
Several environmental and care elements directly impact the growth rate and overall health of the Blue Candle Cactus. Optimizing these conditions encourages more vigorous development.
Light
Ample sunlight is a primary requirement for the Blue Candle Cactus to grow effectively. It thrives in full sun, ideally receiving at least six hours of direct sunlight daily. For indoor cultivation, placing the plant near a bright south or west-facing window is often recommended to provide sufficient light. Insufficient light can lead to stunted growth and etiolation, where the stems become stretched and pale.
Watering
Proper watering is fundamental for this cactus, which prefers a “soak and dry” method. This involves thoroughly watering the plant until water drains from the bottom, then allowing the soil to dry completely before the next watering. During the active growing season in spring and summer, watering may occur every two to three weeks, or even every 7-10 days depending on temperature and humidity. Overwatering, particularly in poorly draining soil, can cause root rot and significantly hinder growth. In cooler months, watering should be reduced as the plant enters dormancy.
Soil
A well-draining soil mix is essential to prevent waterlogging and promote healthy root development. A cactus mix with good drainage, often containing perlite or pumice, is ideal. Adding small gravel to the mix further enhances drainage. This type of substrate mimics the rocky, dry soil conditions of its native Mexican habitat.
Temperature and Humidity
The Blue Candle Cactus prefers warm temperatures, thriving best when temperatures are between 70-90°F (21-32°C). It can tolerate temperatures as low as 50°F (10°C) but should be protected from prolonged frost, as it is only semi-hardy down to about 25°F (-4°C). This species also prefers a low humidity environment, thriving in 30-50% humidity, reflecting its desert origins. Good air circulation is beneficial, especially in more humid climates, to prevent issues.
Nutrients (Fertilization)
During its growing season from spring to early fall, the Blue Candle Cactus benefits from regular, dilute fertilization. A low-nitrogen cactus fertilizer can be applied monthly, typically at 1/4 strength, to encourage growth and flowering. Fertilizing should be reduced or stopped entirely during the winter months when the plant is dormant. Maintaining a balanced nutrient supply supports vigorous stem development and overall plant vitality.
Mature Size and Lifespan
In its native habitat, the Blue Candle Cactus can reach impressive heights of 10 to 15 feet (3 to 4.5 meters), forming a wide, branching structure resembling a candelabra. When grown in pots, its size typically remains more compact, often reaching 3 to 5 feet tall indoors. This cactus can live for many decades with proper care, gradually developing its characteristic tree-like form and taking 10 to 20 years to reach its full height. Repotting every few years is important for potted plants to allow sufficient room for root growth and continued development.
Troubleshooting Growth Issues
When a Blue Candle Cactus shows signs of inhibited or abnormal growth, it often points to underlying environmental or care problems.
Stunted growth
Stunted growth, where the plant appears to stop growing or develops very slowly, can stem from inadequate light or improper watering. Overwatering, which can lead to root rot, also severely impacts the plant’s ability to absorb nutrients and water, thus stunting growth. Ensuring a well-draining soil mix and adhering to the “soak and dry” watering method can help resolve these issues.
Etiolation
Etiolation is a common issue characterized by stretched, pale, and weak stems, indicating a severe lack of light. This happens as the plant attempts to grow towards a light source. Moving the cactus to a brighter location, such as a south or west-facing window, or supplementing with a grow light, can correct etiolation and promote more compact, healthy growth. Once etiolated growth occurs, it usually does not revert to its original form, and affected sections may need to be pruned if desired.
Unusual discoloration
Unusual discoloration, such as browning or mushy spots, often signals overwatering or fungal issues. If the base of the cactus becomes brown and soft, it is likely suffering from rot due to excessive moisture or poor drainage. Allowing the soil to dry out thoroughly between waterings and ensuring adequate drainage are important preventative measures. Fungal spots, appearing as small white or brown marks, may also occur and can sometimes be treated with a fungicide. Conversely, a pale or yellowing appearance could suggest a need for more light or nutrients.