Nun orchids get lumped in with delicate greenhouse plants. The phaius tankervilleae orchid is actually one of the toughest terrestrial orchids a home gardener can grow. It thrives in the ground in warm climates and grows just as well in a large pot further north.
Pleated leaves reach three feet, and flower spikes push up three to four feet tall. Each spike carries brown, white, and rose flowers in late winter and spring. The hooded shape of every bloom gives the plant its common name, the nun orchid.
What Is the Phaius Tankervilleae Orchid?
The phaius tankervilleae orchid grows naturally across parts of Asia, Australia, and the Pacific. Wild populations turn up in China, Hong Kong, Taiwan, Malaysia, and Indonesia. Plants grow in lower montane woods and grassy, moist depressions up to about 1300 meters elevation.
Flowers open to about 4.5 inches across. Growers also call this species the swamp orchid, the lesser swamp orchid, or the monk orchid. All three names point to the same tough terrestrial plant.
Plants need several years of growth before they bloom, often around five years from a small division. A swing of 15 to 20 degrees between day and night temperatures also helps trigger flowering. Steady, mild conditions without that swing can delay blooms for a season.
The nun orchid belongs to the wider group of ground orchids that grow in soil instead of bark. That group includes several genera with very different hardiness, so treat each one on its own terms.
Is the Nun Orchid Naturalized in Florida or Hawaii?
The nun orchid did not start out in the United States. It has naturalized in parts of Florida and in Hawaii, where warm, humid conditions suit it well. It has also been documented as an invasive species in Hawaii and in Jamaica.
Gardeners in those states should check local extension or invasive plant guidance before planting near natural areas. A pot on a patio carries none of that risk. Ground planting near wetlands or preserves is where the concern actually applies.
Its tiny seeds travel easily on wind and water, which helps the species spread once established. That same trait means self sown seedlings sometimes appear near an existing planting. Remove unwanted seedlings early if spreading nearby is a concern.
What Hardiness Zone Does the Nun Orchid Need?
The phaius tankervilleae orchid grows outdoors year round in zones 9b to 11. Gardeners farther north grow it in a container instead. A hard frost damages the leaves, even where the roots underground survive.
Move potted plants indoors or into a sheltered spot before the first frost hits. For more on what orchids tolerate outside, see this guide to whether orchids can live outside.
In colder regions, a container lets you move the whole plant to shelter fast. An unheated garage or bright porch works for the coldest weeks of the year. Bring it back outside once nighttime lows stay above 45 F (7 C).
Garden Placement and Soil
Nun orchids want bright shade, not direct sun. Rich, moist soil that drains well suits them best. A layer of mulch keeps roots cool and holds moisture between waterings.
Shelter the planting spot from strong wind, since the tall spikes can snap. A spot under high tree canopy or near a wall works well. For more layout ideas, see these orchid garden ideas for shaded beds.
In the ground, nun orchids need little disturbance once established. In pots, plan to repot every couple of years as the mix breaks down. Wait several weeks after repotting before starting regular fertilizer again.
Growing a Phaius Tankervilleae Orchid in Pots
Potted culture works well outside zone 9b. Choose a large pot and a rich mix with added bark for drainage. Water often during active growth, since this species does not like to dry out completely.
Feed regularly through spring and summer at quarter to half label strength. Cut back on both water and fertilizer once growth slows in fall. A bloom booster is not necessary for good flowering.
Pick a wide, heavy pot so top heavy flower spikes do not tip it over. Mix two parts bark with one part rich potting soil for drainage and moisture. Terra cotta and heavy ceramic pots both work well for this plant.
Winter Care and Cutting Back
Leaves can look tattered after a light frost or after the plant finishes blooming. Cut the damaged leaves back at that point. New growth replaces them from the base once warmer weather returns.
This kind of cutback does not harm the plant when done after bloom or frost damage. Doing it earlier just removes leaves the plant still needs. For general seasonal guidance, see this article on orchid care in winter.
Established plants tolerate a light, brief frost with only leaf damage. A hard freeze can kill unprotected roots, especially in a shallow pot. Mulch around ground grown plants before the first cold snap arrives.
How to Propagate a Nun Orchid
Division is the standard way to propagate a phaius tankervilleae orchid. Split the clump when it outgrows its pot or spot, keeping several growths per division. For step by step guidance, see this piece on how to divide orchids.
Spring, right as new growth starts, is the best time to divide. Each division needs at least two or three healthy growths to reestablish well. Water new divisions lightly until fresh roots appear.
Nun orchids also have a well known trick that surprises new growers. After the flowers fade, cut the spent flower spike. Lay it on damp sphagnum moss in a shaded, humid spot.
Plantlets sprout from the old floral bracts in about 2 to 3 months. Let them grow on for about 6 months before potting them up separately. Keep the moss consistently damp during that whole stretch.
Common Pests on Nun Orchids
Snails and slugs are the most common outdoor problem, since they chew new leaves and flower buds. Spider mites show up in dry indoor air instead. Scale, mealybugs, and thrips also turn up occasionally on stressed plants.
Good airflow and dry foliage overnight prevent most of these problems.
Streaks, blotches, or crinkling on leaves, roots, or flowers usually signal a virus or fungal problem, not a pest. There is no cure for a viral infection, so remove and discard affected plants. Clean tools between plants to avoid spreading disease further.
Phaius vs Spathoglottis vs Bletilla
These three genera get confused because all three grow in soil and sit outdoors in warm months. Spathoglottis is the genus commonly sold as ground orchids at nurseries. Bletilla is the hardiest of the three by a wide margin.
| Genus | Hardiness Zones | Height | Bloom Season |
|---|---|---|---|
| Phaius tankervilleae | 9b to 11 | Leaves to 3 ft, spikes to 4 ft | Late winter to spring |
| Spathoglottis | 10 to 11 | 1 to 3 ft | Nearly year round in warm climates |
| Bletilla | 5 to 9 | 1 to 2 ft | Spring |
Bletilla is the one most gardeners outside the deep South can actually grow outdoors. It gets full coverage in this guide to hardy orchids for cold climates. Spathoglottis stays a warm climate plant much like Phaius.
A phaius tankervilleae orchid rewards patience more than fuss. Give it shade, moisture, and a winter cutback, and it comes back reliably for years. That mix of toughness and unusual flowers is why growers keep it around.
Sources
- University of Florida, Institute of Food and Agricultural Sciences: Orchids, Gardening Solutions. https://gardeningsolutions.ifas.ufl.edu/plants/ornamentals/orchids.html
- Internet Orchid Species Photo Encyclopedia: Phaius tankervilleae species page, orchidspecies.com. https://orchidspecies.com/phaiustankervillii.htm
- USDA PLANTS Database: Phaius tankervilleae plant profile. https://plants.sc.egov.usda.gov/plant-profile/PHTA7
Frequently asked questions
What is a phaius tankervilleae orchid?
It is a large terrestrial orchid known as the nun orchid or swamp orchid. It has pleated leaves to three feet and tall spikes of brown, white, and rose flowers in late winter and spring.
Is the nun orchid invasive?
It has naturalized in parts of Florida and Hawaii and is documented as invasive in Hawaii and Jamaica. Gardeners near wild areas in those states should plant it with care.
What hardiness zone does a nun orchid need?
It grows outdoors year round in zones 9b to 11. Gardeners farther north grow it in a large pot and bring it under cover before frost.
How do you propagate a nun orchid from the flower spike?
Cut the spent spike after bloom and lay it on damp sphagnum moss in a shaded, humid spot. Plantlets grow from the old floral bracts in about 2 to 3 months.
How is Phaius different from Bletilla and Spathoglottis?
Bletilla is the hardiest of the three, surviving outdoors in zones 5 to 9. Phaius needs zones 9b to 11 and Spathoglottis needs a similarly warm, frost free climate.