PHALAENOPSIS: The Moth Orchid

phalaenopsis flower

Pronounced: fayl-eh-NOP-sis

Moth orchids are the most popular orchids and are very easy to grow in most homes with high humidity being the most difficult growing requirement to meet. Flat, glossy, spreading leaves support arching spikes of large white, pink, striped or yellow flowers. Smaller flowered varieties with greater numbers of flowers (multi-floral), or varieties with brighter colors and fewer flowers (novelty) are also popular.

Healthy Phalaenopsis start with healthy roots:

  • Pot in a coarse medium. Beginners should avoid moss and soil based mixes as they may remain too wet. Fir bark mixtures are best, with 1.5 to 2.5 cm chunks of bark.
  • Repot when medium starts to decompose. Check yearly, on newly purchased plants or if leaves are limp.
  • Remove old medium if it is loose and any rotting roots; choose a plastic pot that will only just hold the roots of the plant and center plant in new pot.
  • Phalaenopsis may grow roots over the side of the pot and up into the air. Leave these roots on the plant, perhaps misting them when the plant is watered.
  • Roots should be moist at all times. Water when medium has begun to dry but is still damp. Water thoroughly, particularly if your water has a high mineral content.
  • Do not use water softened in salt-consuming water softeners. Low mineral water is preferred, such as naturally soft water or rain water. If hard water is used, water very heavily to flush minerals. Use room temperature or warmer water.
  • Avoid leaving water standing in the crown of the plant as this causes fatal rot.
  • Fertilize weakly and frequently with a balanced fertilizer. One-eighth to one-quarter strength recommended by manufacturer for house plants every week in spring and summer and every two weeks in autumn and winter.

Healthy leaves produce more and bigger flowers:

  • Low light levels are appropriate. Leaves should be a medium green, not yellowish or dark green. They should be firm, not long and floppy (more light needed). A dark red blush covering the top of the leaves means too much light.
  • One to two hours of sunshine on a windowsill (East recommended) or 15-30 cm under a two tube fluorescent fixture.
  • Leaves should be firm; if soft and desiccated, check roots for rot, and repot if necessary. High humidity (such as enclosing the plant in a plastic bag) will aid recovery if most or all of roots lost, but be careful of rot.
  • Phalaenopsis do best with 60-70% humidity, but will grow and bloom, although more slowly and with fewer and smaller flowers, in lower humidity. Use humidifier to raise humidity – humidity pans and misting rarely effective. Enclosing plant growing areas is effective but ensure fresh air and air movement to avoid mold and rot.
  • Grow Phalaenopsis in warm temperatures with 18°C minimum winter nights (except if forcing flowering) and 32°C summer day maximum. Ensure 6-12°C day/night difference to aid flower formation.

Moth orchids usually bloom annually and the flowers last for several weeks:

  • Maintain plant orientation while spike is growing for best display.
  • Buds turning yellow, wilting and falling prior to opening is from not enough energy in the plant to open the flower either because the light is too dim, the plant is too small, or the roots have rotted. Also caused by ethylene gas (produced by ripening fruit), or too great a temperature variation.
  • On healthy plant, a second set of flowers may result if spike cut back to one of the non-flowering nodes on the flower stem after the first flowers fall. Do not try this if the plant is not healthy and growing new roots and leaves.
  • If healthy, mature plant fails to bloom, provide slightly brighter light and lower night temperatures (14°C nights) for the month of October.
  • If leaves start to wilt while the plant is blooming (or at any other time), cut off the flower stem at the base, and check for broken down potting medium and rotting roots.

Copyright © Canadian Orchid Congress 2003.


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