Myrtillocactus Geometrizans (mir-til-oh-KAK-tus, jee-oh-MET-rih-zans), also known by the scientific names of:
- Cereus Geometrizans
- Myrtillocactus Grandiareolatus
- Myrtillocactus Geometrizans (Mart. Ex Pfeiff.)
It is a member of the family Cactaceae and the best-known species of the genus Myrtillocactus.
Myrtillocactus comes from the Greek word myrtillus, which means small myrtle, and cactus.
Geometrizans, on the other hand, refers to the geometric markings (formal pattern) on the plant.
The plant is native to the northern and central Mexico down to Oaxaca, where it is widespread in tropical deciduous forests and xerophilous scrub.
It is also prevalent in the Chihuahuan desert.
Due to its blue-green color and growth habit, the plant has acquired several common names.
The most popular and widely used ones are:
- Blue candle
- Blue myrtle cactus
- Whortleberry cactus
- Bilberry cactus
Other Popular Columnar Succulents include:
Blue Candle Cactus Care
Size & Growth
Blue candle is a fast-growing columnar succulent tree cactus which grows up to 13’ to 16’ feet tall.
Featuring 2” to 4” inch thick blue-green or blue-grey glaucous stems with multiple areoles and 5 to 8 ribs, the plant remains unbranched for a long time, but produces several branches upon maturity, resembling candelabra.
Hence, the common name, blue candle.
The stems are succulent and have small spines, growing from the areoles.
Upon maturity, the plant displays a dense growth of stems, which are highly branched and closely growing.
In its natural habitat, the crown of the plant can spread up to 8’ to 12’ feet in width.
Flowering and Fragrance
The columnar candelabra cactus produces small creamy or greenish-white flowers in spring after it has grown to about 2’ feet in height.
While the flower color is initially white it later changes to dark red.
The flowers are fragrant and attract pollinators.
Flowering is followed by the production of small dark purple berry-like oblong fruits, which resemble the fruit of Vaccinium myrtillus, called whortleberry or bilberry.
Myrtillocactus geometrizans’ common names whortleberry cactus and bilberry cactus are based on this resemblance.
The fruit, known as garambullo, has a sweet flavor and is edible.
Light & Temperature
Like all other cacti and succulents, the blue candle needs sunlight to grow properly.
However, do not expose the young plants to direct full sun; keep them in light shade until they reach maturity and then shift to a sunny location.
The plant is only semi-hardy and can only tolerate temperatures down to 25° degrees Fahrenheit (-4° C).
Protect your blue candle plants from extremely cold weather and frost or they may die.
Due to its poor winter hardiness, do not expose the plant to the nighttime temperatures below 50° degrees Fahrenheit (10° C) to ensure proper growth.
In the United States, blue myrtle is hardy to USDA zones 9a to 11b.
Watering and Feeding
This shrubby cactus species is fairly drought-resistant but appreciates watering in summer.
However, it cannot tolerate standing water.
Good advice for watering whortleberry cactus is to water thoroughly once and then let the soil dry out before watering again.
Also, avoid overhead watering.
Reduce the watering to only a bare minimum in winter to prevent the soil from being cold and wet for extended periods of time, as it can lead to root loss.
For best growth, feed your blue myrtle with a specialized cactus fertilizer once a month during the spring and summer seasons.
Soil & Transplanting
Bilberry cactus needs a well-draining soil mix as it cannot tolerate wet or waterlogged soil.
Adding some gravel to the soil can help improve its drainage.
Since this cactus species display a fast growth-rate and grow to form big dense shrubs, they need plenty of space to grow and are likely to need repotting almost every other year.
Grooming and Maintenance
While this candelabra like cactus species is easy to grow and doesn’t need pruning or too much care, once established, you need to be careful about the light exposure and water to ensure the best growth.
The plant also needs to be protected from extremely cold weather to stay alive.
How to Propagate Myrtillocactus Geometrizans
Blue myrtle cactus are either grown from seeds or multiplied through stem cuttings in summer.
Collect seeds from ripe fruits, clean and dry them and then sow directly into the ground, after the end of the frost season.
When propagating from cuttings, let their cut surfaces dry out (callous) for 2 to 3 weeks before planting them into the soil.
Water once and then let the soil dry out before watering again.
Cuttings only root in warm/hot weather.
Myrtillocactus Geometrizans Pest or Diseases
While m. geometrizans isn’t susceptible to many diseases and pests, it can develop root rot if left in damp and poorly drained soils for extended periods of time.
Blue myrtle is attractive to birds, butterflies, bees, and moths.
Blue Candle Cactus Uses
Blue candle is a popular cactus species for cultivation.
It is widely used as grafting stock for cacti plants and for adding visual interest to landscapes.
The fruits of the plant are widely consumed in Mexico due to which it is also grown for commercial purposes.
Several crested clones of Myrtillocactus geometrizans are also available.