The Blue Myrtle Cactus (Myrtillocactus geometrizans) is a distinctive columnar cactus native to central and northern Mexico. Admired for its striking blue-green stems, it develops a candelabra-like, tree-like structure as it matures. This species is a popular choice for indoor and outdoor cultivation due to its unique appearance and low maintenance, thriving in arid environments.
The Blue Myrtle Cactus Flower
The Blue Myrtle Cactus produces small, unassuming flowers, typically greenish-white or creamy white. These funnel-shaped blooms emerge from mid-spring to summer, offering a subtle contrast to the cactus’s blue-green stems.
The flowers open at night, are nocturnal, and are often short-lived, sometimes lasting only a single day. They develop from areoles along the stems, which are small, cushion-like structures from which new growth emerges. Rich in nectar, these flowers serve as a food source for nocturnal pollinators. Blooming typically begins when the cactus reaches maturity, often around two feet in height.
Encouraging Blooms
Encouraging the Blue Myrtle Cactus to bloom requires specific environmental conditions and consistent care, mimicking its native arid habitat. Adequate light exposure is important for flower production. The cactus thrives in full sun, needing at least six hours of direct sunlight daily to promote healthy growth and blooming. While it can tolerate some partial shade, insufficient light often results in reduced vigor and a lack of flowers.
Temperature plays a significant role in initiating flowering, particularly a cool winter dormancy period. Ideal daytime temperatures during the growing season range from 65 to 85 degrees Fahrenheit (18-30°C). During winter, a cooler period around 35 degrees Fahrenheit (1.6°C), but not below 25 degrees Fahrenheit (-3.9°C) for prolonged periods, helps trigger the spring bloom cycle. This temperature differential signals the plant to prepare for reproduction.
Watering practices must align with the cactus’s natural drought tolerance. During the active growing season in spring and summer, water thoroughly, allowing the soil to dry completely between waterings. Overwatering is a common issue that can lead to root rot and inhibit flowering. In cooler winter months, watering should be significantly reduced, often to about once a month or less, to support the plant’s dormancy.
The right soil composition is also important for blooming. The Blue Myrtle Cactus requires a very well-draining soil mix, typically a sandy texture, similar to desert soil. A specialized cactus or succulent potting mix, amended with coarse sand or perlite, ensures proper drainage and aeration, preventing waterlogged roots. While not heavy feeders, a low-nitrogen fertilizer for cacti and succulents can be applied once a month during the spring and summer growing season to support overall plant health and flower development. Fertilization should cease during the dormant winter period.
Pollination and Fruit
After flowering, successful pollination leads to the development of the Blue Myrtle Cactus’s distinctive fruit. Nocturnal pollinators, such as moths and bats, are attracted to the nectar-rich flowers, facilitating pollen transfer for fruit set.
The fruit, known as “garambullos” in Mexico, is small, spherical, and typically dark red or blue-purple when ripe. It resembles blueberries or bilberries, reflected in some of the cactus’s common names. The edible fruit has a sweet, juicy flavor and is consumed fresh or used in jams and desserts.
The duration from flowering to fruit ripening varies, but generally, the small berries follow the short-lived blooms. These fruits serve as a mechanism for seed dispersal in the plant’s natural habitat.