The Nuns Cap Orchid (Phaius tankervilleae), also known as the Chinese Ground Orchid, is a striking terrestrial orchid. Prized for its unique, nun’s cap-like blooms on tall stalks, its adaptability makes it a favored choice for both novice and experienced plant enthusiasts.
Understanding the Nuns Cap Orchid
Distinctive Features
Nuns Cap Orchids are recognized by their large, pleated leaves, forming a verdant clump up to 3 feet long and 6 inches wide. These leaves emerge from sturdy, ovoid pseudobulbs. The plant produces tall, erect flower stalks, often reaching 3 to 4 feet in height, carrying clusters of 10 to 35 showy flowers. Individual flowers can measure up to 5 inches across and display colors like rusty brown, maroon, white, yellow, and purple, often with a contrasting lip. The unique hooded shape of the upper sepal and petals resembles a nun’s veil, giving the orchid its common name.
Origin and History
Native to tropical and subtropical Asia, including China, India, Thailand, Malaysia, Indonesia, the Pacific Islands, and Australia, the Nuns Cap Orchid thrives in open, grassy areas, damp deciduous forests, and moist depressions, often at altitudes up to 1300 meters. John Fothergill introduced this species to England from China in 1778. It was the first tropical orchid to flower there, blooming in Lady Emma Tankerville’s greenhouse, after whom it was named in 1788 by Sir Joseph Banks.
Essential Care for Nuns Cap Orchids
Light Requirements
Nuns Cap Orchids thrive in bright, indirect light, similar to their natural woodland habitats. They can tolerate some direct morning sun, but intense afternoon sun causes leaf burn. Indoors, an east or north-facing window is ideal; sheer curtains can diffuse light from south or west-facing windows. Insufficient light leads to weak, leggy growth and darker leaves, while too much light may cause leaves to yellow or develop brown spots.
Watering Practices
Nuns Cap Orchids prefer consistently moist, but not waterlogged, soil. Overwatering causes root rot (mushy, dark roots and foul smell), while underwatering causes leaves to shrivel. Water thoroughly when the top inch or two of the potting mix feels dry, typically once a week. Morning watering allows leaves to dry, preventing fungal issues. During winter, reduce watering to prevent the plant from completely drying out, especially if it loses leaves.
Temperature and Humidity
Nuns Cap Orchids thrive in warm environments, with an optimal daytime temperature range of 65-75°F (18-24°C). They tolerate temperatures as low as 40°F (5°C), but prolonged exposure below 35°F (1.7°C) can cause severe damage. A cooler winter period, around 55-60°F (13-16°C), benefits bud setting. Suitable humidity levels are around 50%, maintained with a humidity tray or cool-mist humidifier indoors. Good air circulation is important in humid conditions to prevent fungal diseases.
Potting Medium and Repotting
A well-draining terrestrial orchid potting mix is essential. Suitable mixes often include peat, compost, decomposed pine bark, fir bark, sphagnum moss, perlite, or pumice. A common ratio is 60-70% organic matter (like peat and pine bark) with added perlite and sand for drainage. Repot every two to three years, or after flowering, to refresh the medium and provide room for root growth. When repotting, choose a deep pot and avoid packing the mix too tightly for proper aeration.
Fertilization
Nuns Cap Orchids are heavy feeders. During active growth (spring through fall), fertilize bi-weekly with a balanced, water-soluble orchid fertilizer (e.g., 20-20-20). Dilute fertilizer to half or quarter strength to prevent root burn. Slow-release fertilizer can be applied every three months, or organic options like fish emulsion or compost tea every two weeks during the growing season. Reduce fertilization to monthly or stop during the winter rest period.
Encouraging Blooms and Propagation
Promoting Flowering
To encourage abundant blooms, Nuns Cap Orchids need consistent bright, indirect light year-round. Insufficient light is a common reason for lack of flowering. A cool winter rest period with nighttime temperatures around 55-60°F (13-16°C) can trigger bud formation. Reduced daylight hours in late winter to early spring also stimulate flowering. Proper fertilization, especially with high phosphorus fertilizers during active growth, supports bloom development.
Propagation Techniques
Nuns Cap Orchids can be propagated through pseudobulb division or by rooting spent flower inflorescences. For division, separate pseudobulb clumps from mature plants after flowering, ensuring each new section has at least two shoots and some roots. Pot these divisions in a well-draining orchid mix. To propagate from flower spikes, cut the spent inflorescence and lay it horizontally on moist sphagnum moss or damp sand in a shaded area. New plantlets will develop from the nodes along the stem, typically taking two to three months. Once plantlets have three or four roots, separate and pot them individually.
Common Problems and Solutions
Leaf Issues
Yellowing leaves can indicate too much or too little light, or improper watering. Scorched spots on yellow leaves suggest too much direct sunlight. Weak, leggy growth with dark green leaves signals insufficient light. Overwatering often causes overall yellowing and mushy leaves due to root rot, while underwatering causes shriveling. Brown leaf tips can suggest low humidity or inconsistent watering.
Lack of Blooms
The primary reason Nuns Cap Orchids may not bloom is inadequate light. Ensure consistent bright, indirect light, supplementing with grow lights if needed. Lack of a cool winter rest period can also inhibit flowering, as a temperature drop initiates bud production. Improper watering, either too much or too little, can stress the plant and prevent flowering. Nutrient deficiencies can also play a role, so maintain a consistent fertilization schedule.
Pests and Diseases
Nuns Cap Orchids are generally robust but can encounter pests like aphids, mealybugs, and scale insects. Aphids, found on new growth and buds, can be dislodged with water or treated with insecticidal soap. Mealybugs, appearing as white, cottony masses, can be removed with an alcohol-dipped cotton swab or insecticidal soap. Scale insects attach to leaves and pseudobulbs; minor infestations can be wiped off with alcohol, while severe cases may need specific insecticides. Fungal issues, such as black spots or bud yellowing, can arise from overwatering or poor air circulation. Good air movement and avoiding water on leaves help prevent these problems.