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Vanda Alliance


The Vanda Alliance, as this varied group of plants is called,
is made up mostly of warmth- and sun-loving orchids with very
colorful flowers. Originating from tropical Asia, they are
easily grown in warm climates, where plants are grown outside
in light shade, such as in a lath house. In climates where
winters are cold, they are often summered outside, an grown
inside during the winter in a sunny window, or year-round in a
greenhouse.


LIGHT is a crucial factor in blooming some vandaceous plants.
There are three types of vandas: strap-leaf, semiterete and
terete. The first type has broader, flat leaves, while terete
types have round, pencil-shaped leaves. The semi-teretes are
hybrids between the two, with an intermediate shape. Terete
types need full sun, and are best grown in high light climates.
In warm, bright climates, you can grow any type of vanda,
outside (if warm) with partial shade for strap-leaf types and
semiteretes (especially in midday in summer) or inside (when
cold) in a bright, south window. In climates where winters are
dull, try strap-leaf types (or ascocendas); grow them outside
in summer an in full sun inside during the winter. In a
greenhouse, give the plants about 25% to 35% shade, less in
winter if dull. Leaves should be a medium green, not dark
green.


TEMPERATURE for most vandas should be warm; a minimum winter
night temperature of 55 degrees F is recommended. Colder spells
can be tolerated for a short time if it is not windy. Optimum
temperatures are 60 degrees F at night, and a maximum of 95
degrees F during the day. Warmer temperatures mean faster
growth, which must be balanced with higher humidity, air
movement, and increased water and fertilizer. Days should be
warm and humid for optimum plant growth.


WATER. Vandas generally like lots of water when growing, but
must dry quickly. Because of this, and their extensive root
system, they are mostly grown in slatted wood baskets, or in
pots with a coarse potting medium. If warm and sunny, they may
need daily watering, with misting several times a day in dry or
hot climates. Water sparingly in the winter or during cloudy
weather, but do not allow plants to shrivel.


HUMIDITY of 80% is ideal. In tropical climates this may be easy
to obtain. Yet in most climates, misting may be necessary
during sunny weather. In a greenhouse, this is easier to
provide by wetting down the floor, or using an evaporative
cooler. In the home, place the plants on trays of gravel,
partially filled with water. Do not mist the plants if the
leaves will not dry by nighttime. Air movement must be strong.


FERTILIZING. A well-balanced (20-20-20) fertilizer applied full
strength once a week is recommended when warm, or use 1/4
strength every watering. During cool or cloudy weather, apply
fertilizer once every two to four weeks. Use a high-phosphorus
fertilizer (such as 10-30-20) ever third application to promote
blooming. A vitamin B1 compound may be beneficial; use it once
a month.

POTTING should be done in the spring. Plants in baskets do not
need to be repotted often; leave them unless the potting medium
breaks down. Just set the plant, with the old basket, into a
container of water to make the aerial roots more pliable, and
then set plant and basket into a larger basket. For plants in
pots, repot in a slightly larger pot, positioning the plant in
the center. Use a coarse medium, whether fir bark, treefern,
charcoal, etc., and work it around the roots. Keep shaded,
humid, but drier at the roots until new root tips grow. Do not
overpot.

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

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