Pronounced: den-DROH-bee-um
So called because of the resemblance between their flowers and those of the Phalaenopsis or moth orchid, the vigorous and easy to grow plants produce large numbers of flowers through the year, in colors of white, pink, purple and combinations. The upright plants trace their ancestors to South East Asia and Australia. The genus Dendrobium contains hundreds of different species of which the plants discussed here are only a small part. Other Dendrobiums may have radically different cultural requirements.
Healthy Dendrobiums start with healthy roots:
- Pot in a coarse medium. Fir bark mixtures are best, with 1.5 to 2.5 cm chunks of bark, perlite and charcoal.
- Repot when the growth has reached the edge of the pot or if the medium is beginning to decompose (usually after about two to three years). Repot as new growths are just starting to form.
- Remove old medium if it is loose and any rotting roots; choose a plastic pot just big enough to hold the roots, and position the plant so that the new growths will have room to grow without reaching the edge of the pot.
- These plants like a rapid drying cycle – grow in the smallest possible pot. The plants may become top heavy and require the plastic pot be slipped into a clay pot to lower the center of gravity.
- Roots should be moist at all times when the plant is in active growth but should dry out somewhat as the growth matures and when the plant is not actively growing.
- When watering, water thoroughly, with a volume of water at least equal to that of the pot.
- 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.
- 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:
- Medium to high light levels are appropriate. Leaves should be a light green, not yellowish (too much light) or dark green (too little light). They should be somewhat stiff, not long and floppy (more light needed). A reddish edge to the leaves indicates the light is on the upper boundary of a proper level of light.
- Two to four hours of sunshine on an East, West or South window sill, or under HID sodium or metal halide lamps. A bank of 4 to 8 fluorescent tubes may also be successful for miniature varieties. With full sized plants reaching 1 – 1.5 m, fluorescent light is not likely to be effective for the larger plants.
- Sticky, honey-like sap may form on stems and leaves. This is a natural occurrence in high light, but may also signal an insect infestation. Examine your plant carefully for pests should this occur.
- Dendrobiums do best with 60-70% humidity but will grow and bloom at somewhat lower humidity levels. Use humidifier to raise humidity – humidity pans and misting minimally effective. Enclosing plant growing areas is ffective
- but ensure fresh air and air movement to avoid mold and rot.
- Dendrobium phalaenopsis hybrids are warm growing, with night minimum temperatures of 18°C and day maximums of 32°C.
Dendrobium phalaenopsis may bloom at any time during the year and the flowers last for four to eight 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, the roots have rotted. Also caused by ethylene gas (from ripening fruit) or drastic temperature changes.
