The Nun’s Orchid (Phaius tankervilleae) is a terrestrial orchid known for its striking beauty and ease of cultivation. Native to tropical and subtropical regions of Asia, Australia, and Africa, including China, this adaptable plant boasts large, showy flowers and broad, pleated leaves. Its common name comes from its unique hooded flowers, which often feature rusty brown petals and a purplish lip.
Essential Growing Conditions
Light
Nun’s Orchids thrive in bright, indirect light. Placing your orchid near an east-facing window or in a location that receives filtered sunlight is ideal. Direct, intense sunlight, especially during the hottest parts of the day, can scorch the leaves and hinder growth. If the leaves appear yellow or bleached, it indicates too much light, while dark green leaves suggest insufficient light, which can also impede blooming.
Watering
Consistent moisture without waterlogging is key for Nun’s Orchids. Water regularly, typically every week, ensuring good drainage to prevent root rot. Allow the top inch or two of the potting medium to dry slightly between waterings, but avoid letting the plant become completely dry for extended periods. Watering in the morning helps ensure any moisture on the foliage evaporates before cooler evening temperatures set in, reducing the risk of fungal issues.
Temperature and Humidity
Nun’s Orchids prefer warm temperatures, with an ideal range between 60-80°F (15-29°C) during the day and a slight drop of 10-15°F (6-8°C) at night. While they can tolerate temperatures as low as 40°F (5°C), prolonged exposure to cold can damage the plant, and temperatures below 32°F (0°C) are harmful. Maintaining consistent humidity levels, ideally around 50-70%, benefits their health. You can increase humidity by placing the potted orchid on a pebble tray filled with water, using a room humidifier, or by frequently misting the plant, though avoid wetting the foliage excessively.
Feeding and Potting Medium
Fertilizing
Nun’s Orchids are heavy feeders, requiring regular fertilization to support their vigorous growth and flowering. During active growth periods, apply a balanced, water-soluble orchid fertilizer (e.g., 20-20-20) at quarter or half strength every one to two weeks. Organic options like fish emulsion or compost tea can also be applied every two weeks. Reduce fertilization to monthly or stop entirely during the winter or dormant period.
Potting Medium
A well-draining yet moisture-retentive potting medium is important for Nun’s Orchids, as they are terrestrial. A suitable mix often includes components like fir bark, sphagnum moss, perlite, or pumice to ensure good aeration and drainage. Common recommendations include blends of peat, well-rotted compost, partially decomposed pine bark, or equal parts bark mulch and peat. Ensuring the mix is loose and not compacted helps prevent waterlogging and promotes healthy root development.
Repotting Your Orchid
Repotting a Nun’s Orchid is recommended every two to three years, or when the plant shows signs of outgrowing its pot. Indicators for repotting include roots growing out of the drainage holes, the potting medium breaking down and becoming compacted, or new growth extending over the pot’s edge. The best time to repot is after the plant has finished flowering in late winter or early spring, allowing it to establish new roots before the next growth cycle. Choose a pot only one size larger than the current one, ensuring it has adequate drainage holes.
When repotting, gently remove the orchid from its old container and shake off old potting mix. Inspect the roots, trimming any dead, shriveled, or rotten sections with clean, sharp shears. Position the orchid in the new pot, ensuring the base of the pseudobulbs is level with the top of the fresh potting medium, then fill around the roots, avoiding over-compacting the mix. If dividing the plant, ensure each new section has at least three to four pseudobulbs to support future growth and flowering.
Encouraging Blooms
To encourage abundant blooms, providing the correct environmental conditions is key. Adequate bright, indirect light is a primary factor, as insufficient light can lead to a lack of flowers. A cool winter rest period, with temperatures around 55-60°F (13-16°C), helps trigger bud development. During this cooler period, reduce watering, providing just enough to prevent the plant from drying out completely.
Consistent care throughout the year, including proper fertilization during active growth, contributes to the plant’s overall vigor and ability to produce flowers. After the orchid finishes blooming, you can prune the spent flower spikes at their base to encourage new growth.
Addressing Common Issues
Yellowing leaves on a Nun’s Orchid signal several issues, with improper watering being a common cause. Both overwatering, which can lead to root rot, and underwatering, causing dehydration, can result in yellow foliage. Yellowing may also indicate too much direct sunlight, nutrient deficiencies (especially nitrogen or magnesium), or natural aging of older leaves. Adjusting watering practices and ensuring the plant receives appropriate light and nutrients often resolves this.
Browning leaf tips often point to low humidity or the presence of chlorine or other chemicals in the water. Increasing humidity with pebble trays or humidifiers and using filtered or rainwater helps. Common pests include mealybugs, scale insects, and aphids, which cause stunted growth and distorted leaves by sucking plant sap. Manual removal with an alcohol-dipped cotton swab or applying insecticidal soap manage these pests. Poor air circulation contributes to fungal issues like Botrytis, which is prevented by ensuring good airflow around the plant.