The Grandiflorus cactus, botanically known as Selenicereus grandiflorus, captivates with its extraordinary nocturnal blooms. This plant is renowned for its large, fragrant flowers that unfurl only after dusk, offering a unique spectacle. While its common name, Queen of the Night, can refer to several night-blooming cacti, this guide focuses on cultivating the true Selenicereus grandiflorus to enjoy its stunning, ephemeral blossoms.
Meet the Grandiflorus Cactus
The Grandiflorus cactus, Selenicereus grandiflorus, is native to the Antilles, Mexico, and Central America. This climbing or sprawling cactus is also known as Queen of the Night, Night-blooming Cereus, or Vanilla Cactus, reflecting its unique flowering habit and sweet fragrance. Many plants marketed under these common names may be other related species or hybrids, such as Hylocereus undatus (dragon fruit) or Peniocereus greggii, which also produce night-blooming flowers.
Selenicereus grandiflorus features long, slender, often triangular stems that can reach over 20 feet in their natural habitat. These stems are typically green, sometimes with a purplish hue, and bear small spines. Its large, trumpet-shaped flowers can measure up to a foot across. These blooms are typically white or yellowish-white, exuding a strong, sweet, vanilla-like scent that intensifies during their nocturnal opening. Each flower opens for just a single night.
Grandiflorus Cactus Care
Light
Selenicereus grandiflorus thrives in bright, indirect light, mimicking its natural habitat under larger plant canopies. An east-facing window or a shaded south- or west-facing window provides ideal illumination without harsh direct sun. Too much direct sunlight, especially during the hottest parts of the day, can scorch stems, turning them yellow or reddish. Insufficient light leads to leggy, weak growth and may hinder flower production.
Soil and Potting
A well-draining soil mix is essential for the Grandiflorus cactus, preventing waterlogging and root rot. Use a specialized cactus or succulent potting mix blended with additional perlite, pumice, or coarse sand in a 1:1 ratio for optimal drainage and aeration. Choose a pot with drainage holes. A pot size that accommodates the current root ball with a little room to grow is suitable, as excessively large pots can retain too much moisture.
Watering
Watering Selenicereus grandiflorus requires a balanced approach. Water thoroughly when the top two to three inches of soil feel dry, allowing water to drain completely from the pot bottom. During the active growing season (spring through summer), water every 7-14 days, depending on environmental conditions. Reduce watering significantly in the cooler, dormant months (fall and winter), allowing the soil to dry out almost completely between applications to prevent rot and encourage a resting period.
Temperature and Humidity
This cactus prefers warm temperatures, ideally 65°F-80°F (18°C-27°C) during active growth. While it tolerates higher temperatures, extreme heat with direct sun can be detrimental. For winter dormancy, a cooler period of 50°F-60°F (10°C-15°C) benefits future blooms. Selenicereus grandiflorus appreciates moderate to high humidity, given its epiphytic nature. Misting stems occasionally or placing the pot on a pebble tray can increase ambient humidity, especially in dry indoor environments.
Fertilizing
During the active growing season (spring to late summer), apply a balanced liquid fertilizer diluted to half strength every 2-4 weeks. Alternatively, use a fertilizer formulated for cacti and succulents, which typically has lower nitrogen and higher phosphorus and potassium, to promote strong stem growth and flowering. Avoid fertilizing during the dormant winter months. Over-fertilization can lead to salt buildup in the soil, damaging roots.
Encouraging the Night Bloom
Encouraging Selenicereus grandiflorus to bloom requires specific environmental cues. Plant maturity is key; younger plants may take several years to flower. A distinct winter resting period is paramount for bloom production, involving reduced watering and cooler temperatures (50°F-60°F / 10°C-15°C) for two to three months. Consistent bright, indirect light during the active growing season helps the plant store energy for flowering. A balanced fertilizer, especially one with higher phosphorus, also supports bloom development. Adequate support for climbing stems contributes to overall plant vigor and flowering.
Propagating Grandiflorus Cactus
Propagating Selenicereus grandiflorus is effectively done through stem cuttings. Select a healthy stem section at least 4-6 inches long, making a clean cut with a sterilized knife or shears. Allow the cut end to “callus over” in a dry, shaded area for several days to a week; this prevents rot. Once callused, insert the cutting 1-2 inches deep into a well-draining potting mix.
While rooting, keep the soil slightly moist but not saturated, and provide bright, indirect light. Roots typically form within a few weeks to a couple of months. Gently tug on the cutting to check for resistance, indicating root development. Once rooted and showing new growth, care for it as a mature plant.
Troubleshooting Common Grandiflorus Cactus Problems
Common issues with Selenicereus grandiflorus often stem from environmental conditions. Yellowing or browning stems can indicate too much direct sunlight or under-watering. Mushy, discolored stems, especially at the base, signal overwatering and root rot, requiring prompt repotting into fresh, dry soil after trimming affected roots.
Lack of flowering, assuming maturity, usually points to insufficient light or an inadequate winter resting period. Pests like mealybugs and scale insects may appear as cottony white masses or small, raised bumps. Treat these by wiping them off with rubbing alcohol on a cotton swab or by applying an insecticidal soap formulated for cacti.