Vanda christensoniana (Ascocentrum christensonianum) - fragrant

Vanda christensoniana, also known by its former name Ascocentrum christensonianum or "Christenson orchid," is a species of epiphytic orchid from the Orchidaceae family, endemic to Vietnam. Named in honor of botanist and taxonomist Eric Christenson, this monopodial orchid is notable for its unusual purple foliage and delicate flowers, being a collector's plant appreciated for its exotic aesthetics and specific care requirements.

Leaf and Flower Appearance

• Leaves: The leaves are elongated, strap-shaped, with a tridentate tip, 10-20 cm long, and have a reddish-green to intense purple color due to the accumulation of anthocyanins, which provide protection against strong sunlight. The purple color is more pronounced in bright light, allowing the plant to thrive in full sun, unlike other Vanda orchids. In low light, the leaves tend to be greener.
• Flowers: The flowers are small, about 1.4 cm in diameter, grouped in erect, axillary inflorescences 10-15 cm long, with 2-4 densely flowered spikes. The color ranges from pale pink to purple or white, with a darker center. They bloom more frequently in spring and autumn (March-May and September-November), each inflorescence producing a bouquet of flowers with a subtle, floral fragrance. The flowers last 2-3 weeks.
• Fragrance: The scent is delicate, more noticeable in warm and humid conditions, but not as intense as other Vanda orchids.

Growth Characteristics

• Height: It is a small to medium-sized orchid, reaching 20-40 cm in height, with an erect stem completely covered by leaf sheaths.
• Vigor: It has moderate growth, typical of monopodial orchids, with long, thick aerial roots adapted to absorb moisture from the air.
• Type: It is a monopodial epiphyte that grows on tree branches in dry, semi-deciduous, or deciduous forests in Vietnam, at altitudes of 0-700 meters.

Growing Conditions

• Exposure: Prefers intense light (35,000-45,000 lux), ideally bright indirect light or filtered sun. It can tolerate direct sun due to its purple leaves, but prolonged exposure to scorching sun should be avoided to prevent burns. Constant air movement is essential. Note that high temperature can be compensated with humidity.
• Soil/Substrate: Grows best without substrate (if humidity is ideal), in hanging wooden baskets or mounted on cork or tree fern to allow aerial roots to breathe. If a pot is used, the substrate must be extremely airy (e.g., bark, perlite, charcoal).
• Watering: Requires daily watering during the growing season (spring-summer), but roots must dry completely between waterings. Morning misting is beneficial on hot, dry days. In winter, watering is reduced, especially in low light conditions.
• Temperature: Prefers a warm to hot climate, with daytime temperatures of 27-32°C in summer and 19-21°C in winter, and daily differences of 6-9°C. Tolerates short cooler periods but not below 16°C.
• Humidity: If grown with free roots, it needs high humidity year-round. Indoors, a humidifier or tray with pebbles and water helps. Growing in pots allows cultivation in low atmospheric humidity conditions, but compensation by misting is recommended.

Care and Resistance

• Fertilization: Apply an orchid fertilizer (e.g., 20-20-20) at 1/4-1/2 of the recommended dose on the package, weekly during active growth. In spring and summer, use a nitrogen-rich fertilizer, and in autumn, one rich in phosphorus to stimulate flowering. In winter, fertilization is reduced or stopped completely.
• Pests: Can be affected by mealybugs, mites, or fungi in conditions of stagnant humidity or very dry air. Regularly inspect roots and leaves, and ensure good ventilation.
• Propagation: Propagated by dividing mature stems or by "keiki" (young plants) that occasionally appear.
• Toxicity: NOT toxic to humans and animals, safe for homes with children or pets.
• Special Care: Avoid low light environments, which reduce leaf color and flowering. Aerial roots should not be cut unless dry, as they are essential for moisture absorption.

Origin

Vanda christensoniana is endemic to southern Vietnam, found in dry, semi-deciduous, or deciduous forests at low altitudes (0-700 meters), growing on tree branches. Discovered relatively recently, it was described in 1993 under the name Ascocentrum christensonianum but reclassified as Vanda in 2012 due to genetic studies that included the genus Ascocentrum within Vanda. It is closely related to Vanda malipoensis and Vanda nana but distinguished by its purple foliage and unique phylogenetic position.

Note: Stock specimens may have leaves with minor mechanical defects.