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Phalaenopsis / Moth orchid

English
  • Indoor Plants
Phalaenopsis 'Leyte Gold'
Photo: Jardin botanique de Montréal (Gilles Murray)
Phalaenopsis 'Leyte Gold'

Onglets

Botany

Origin and description

Genus Phalaenopsis includes more than 60 species native to Indonesia, Malaysia, the Philippines and Australia. These epiphytic orchids live near the edges of tropical forests. Phalaenopsis is a monopodial orchid with no pseudobulb. With a short stem, the small number of leaves are concentrated at its base. It produces showy flower spikes, with blooms that can last for over three months under proper conditions.

Species, cultivars and related plants

They are many phalaenopsis cultivars, all with similar growing conditions.

Common name

Phalaenopsis / Moth orchid

Latin name (genus)

Phalaenopsis spp.

English common name

Phalaenopsis / Moth orchid

French common name

Phalaénopsis

Botanical family

  • Orchidaceae
Horticulture

Growing conditions

Phalaenopsis requires moderate light and appreciates morning sun. Place these plants near an east-facing window. In summer, they may be placed outdoors, protected from the blazing sun. In fall, to encourage blooming, they can be given brighter light by moving them near a west-facing window or closer to the fluorescent tubes if they are grown under artificial lighting.

Ideal temperatures are around 21ºC at night and 25ºC in daytime. In early fall, to initiate blooming, daytime and nighttime temperatures must vary by 5 to 10ºC. These conditions occur naturally from mid-August to late October. Nighttime temperatures should be lowered to 15ºC until the flower spike appears, and then as soon as it begins to lengthen nighttime temperatures should be returned to normal, about 21ºC.

If possible, place the plant in a room with high relative humidity or on a bed of gravel in a water-filled saucer. Place the pot on the gravel, but do not allow the water to touch the base of the pot. During heat spells in summer, it is especially important to keep air circulating around the plant. The rest period for phalaenopsis is not as pronounced as for sympodial orchids.

Easy to grow?

Phalaenopsis is fairly easy to grow in the right location and with proper watering. It is more apt to bloom, any time from December to May, if placed in a cooler room in the fall.

Watering and fertilizer

Because phalaenopsis does not have a pseudobulb, it requires regular watering year-round. The potting medium must never be allowed to dry out completely. Avoid over-watering and never allow water to sit in the crown of leaves, as it could encourage crown rot. It is best to water in the morning with tepid, non-chlorinated water. Allow the water to stand for 24 hours so that the chlorine can evaporate. You can also lightly mist the leaves and any roots growing outside the pot. In summer, allow the medium to dry out to halfway down the pot between waterings. In winter, cut back on watering, allowing slightly more of the medium to dry out.

Orchids grow slowly and appreciate dilute fertilizer at regular intervals during the active growing period, until flowers appear. To avoid burning the roots, chemical fertilizers should be diluted to one-quarter to one-half the recommended strength. There is no need to dilute natural fertilizers. Always fertilize when the medium is moist. Accumulated mineral salts may be flushed as necessary with fresh water.

During the period of active vegetative growth until floral initiation begins (February to mid-August), use a nitrogen-rich fertilizer (NPK ratio: 2-1-1).

During the floral initiation period (mid-August to late October), use fertilizer that is high in phosphorus (NPK ratio: 1-2-1) alternately with balanced fertilizer (NPK ratio: 1-1-1).

Once the flower spike appears, monthly feeding with balanced fertilizer (NPK ratio: 1-1-1) is sufficient. Once the buds open, stop feeding the plant until vegetative growth resumes in spring.

Pruning and maintenance

It is sometimes possible to encourage a plant to rebloom by trimming the flower spike back to beneath the last flower, just above the node with a latent bud. Flush the potting medium with fresh water to remove mineral salt deposits.

Repotting

Phalaenopsis grows best in a small pot. Repot it every two to three years, after blooming, in a light, aerated, well-drained potting medium. You may choose a single material (fern fibre or coconut bark) or combine different materials: redwood bark, rock wool, perlite, diatomite and charcoal. Sphagnum moss is not essential. It can be replaced with rock wool or diatomite (diatomaceous earth). Styrofoam “peanuts” may be placed in the bottom of the pot.

Pests and diseases
  • Aphididae

    Aphids

    There are thousands of species of aphids in the world. These tiny, highly prolific insects feed by sucking the sap from a wide range of ornamental and food plants. They form dense colonies on young shoots and under leaves, and also feed on plant stems, bark, roots and fruit.

  • Pseudococcus adonidum

    Scales (Indoor)

    The scale insect superfamily (Coccoidea) includes several genera of sucking insects capable of damaging indoor plants. Most of them are tropical, non-hardy species, but they adapt very well to our homes.

  • Tetranychus urticae

    Two-Spotted Spider Mite

    Two-spotted spider mites are not true insects, but tiny arthropods, just like other mites and ticks. With their four pairs of legs, they look like miniature spiders. They are so small that they are difficult to see, but they do weave tell-tale whitish webbing.

  • Collar rot
Physiological disorders
Symptoms Possible causes Solutions

Shrivelled and wilted leaves

Too much water

Allow the medium to dry out slightly between waterings
Use a porous, well-drained medium
If necessary, cut leaves back by one-half, remove from pot and trim off any dead roots, then repot in barely moist medium, and provide high relative humidity

No floral initiation

Not enough light
Variation in daytime and nighttime temperatures not enough to initiate blooming
Too much nitrogen to initiate blooming

Place plant in a brighter room or add artificial lighting
Lower nighttime temperatures to 15ºC from October until a flower spike appears
Feed with a phosphorus-rich fertilizer to encourage the plant to bloom

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