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Phalaenopsis

Phalaenopsis the moth orchid, is one of the best orchids for
growing in the home, and is also a favorite with greenhouse
growers. Culture for Doritis, a related genus, and
Doritaenopsis, a hybrid between the two genera, is the same as
for pure Phalaenopsis.


LIGHT is easy to provide for phalaenopsis. They grow easily in
a bright window, with little or no sun. An east window is ideal
in the home; shaded-south or west windows are acceptable. In
dull, northern winter climates, a full south exposure may be
needed. Artificial lighting is excellent. Usually four
fluorescent tubes in one fixture are placed 6" to 1' over the
leaves, 12 to 16 hours a day, following natural daylength. In a
greenhouse heavy shade must be given;70% to 85 shade, or
between 1,000 to 1,500 foot-candles, is optimum. No shadow
should be seen if you hold your hand one foot above the plant's
leaves.


TEMPERATURES for phalaenopsis should usually be above 60
degrees F at night, and range between 75 and 85 degrees F or
more during the day. Although higher temperatures force faster
vegetative growth, higher humidity and air movement must
accompany higher temperatures, the recommended maximum being 90
to 95 degrees F. Night temperatures to 55 degrees F are
desirable for several weeks in the fall, in order to initiate
flower spikes. Fluctuating temperatures can cause bud drop on
plants with buds ready to open.


WATER is especially critical for phalaenopsis. Because they
have no major water-storage organs other than their leaves,
they must never completely dry out. Plants should be thoroughly
watered and not watered again until nearly dry through the pot.
In the heat of summer in a dry climate, this may be every other
day in the winter in a cool northern greenhouse, it may be
every ten days. Water only in the morning, so that the leaves
are dry by nightfall, to prevent rot from occurring on the
leaves.


HUMIDlTY is important to phalaenopsis, the recommended humidity
being between 50% and 80%. In the home, set the plants on trays
of gravel, partially filled with water so that the pots never
sit in water. Mist the plants in dry climates, or during dry
weather, in the mornings only. Grouping plants together raises
the humidity by conserving the water that plants transpire. In
humid climates, as in greenhouses, it is imperative that the
humid air is moving to prevent fungal or bacterial diseases.
Again, leaves should be dry as soon as possible, always by
nightfall.


FERTILIZER should be applied on a regular schedule, especially
if the weather is warm, when the plants are most often growing.
Twice-a-month applications of high-nitrogen fertilizer (30-10-
l0, or a similar formulation) are appropriate in warm, humid
conditions. When flowering is desired a high-phosphorus
fertilizer (10-30-20, or a similar formulation) may be applied
to promote blooming. Some growers apply fertilizer at 1/4
strength with every watering; this is best for warm, humid
conditions. When cooler, or under dull conditions, fertilizer
should be applied once a month.


POTTING is best done in the spring, after blooming.
Phalaenopsis plants must be potted a well-draining mix, such as
fir bark treefern, various types of stone, sphagnum moss, or
combinations of these. Potting is usually done every 1 to 3
years. Mature plants can grow in the same pot until the potting
medium starts to decompose, usually in two years. Root rot
occurs if plants are let in a soggy medium. Seedlings usually
grow fast enough to need repotting yearly, and should be
repotted in a fine-grade medium. Mature plants are potted in
medium-grade medium. When mature, a plant may stay in the same
pot size for many years, but must have the medium changed. To
repot, remove all the old medium from the roots, trim soft,
rotted roots, and spread the remaining roots over a handful of
medium in the bottom of a new pot. Fill the rest of the pot
with medium, working it through the roots, so that the junction
of the roots and the stem is at the top of the medium. Keep the
plant shaded and humid, but drier in the pot, for several weeks
to promote new root growth. A vitamin Bl solution may be
helpful in establishing plants.

Prepared by: Education Committee 
American Orchid Society 
6000 S. Olive Ave. 
West Palm Beach, FL 33405 (407) 585-8666.

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