The Vanda Alliance is
made up mostly of warm- and full-sun-growing
orchids with colorful flowers. Originating in
tropical Asia, they are easily grown in warm
climates, where plants are cultivated outside in
light shade, such as in a lath house. In climates
where winters are cold, they are often summered
outside, and grown inside during the winter in a
sunny window, or year round in a greenhouse.
Smaller growing ascocendas are best outside
tropical conditions.
L I G H T is a crucial factor
in blooming most vandaceous plants. There are
three types of vandas: strap-leaved, semi-terete
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
leaf shape. Terete types need full sun, and are
best grown in high-light climates. In a
greenhouse, give the plants about 25 to 35
percent shade, less in winter if overcast. Leaves
should be a medium green, not dark green. In
warm, bright climates, you can grow any type of
vanda outside (if warm) with partial shade for
strap-leaved types and semi-teretes (especially
in midday in summer) or inside (when cold) in a
bright, south window. In climates where winters
are overcast, try ascocendas. Grow them outside
in summer and in full sun inside during the
winter Be careful to acclimatize plants to avoid
burn.
TEMPERATURES for most vandas
should be warm; a minimum winter night
temperature of 55 F is recommended. Colder spells
can be tolerated for a short time if it is not
windy. Optimum temperatures are 60 to 70 F at
night, and a maximum of 95 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 should be applied
copiously when the plants are growing, but the
roots 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 their situation is warm
and sunny, they may need daily watering. Water
sparingly in the winter or during cloudy weather.
H U M I D I T Y of 80 percent
is ideal. In tropical climates this may be easy
to obtain. In a greenhouse, this is easier to
provide by using an evaporative cooler. In the
home, place the plants on trays of gravel
partially filled with water. Air movement must be
strong.
F E R T I I. I Z E -with a
balanced (such as 20-20-20) fertilizer applied
full strength once a week during warm weather or
use a one-quarter-strength solution at 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)
every third application to promote flowering.
P O T T I N G should be done
in the spring. Plants in baskets do not need to
be repotted often. Leave them unless the potting
medium breaks down. Set the plant, with the old
basket intact, 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 bar, tree fern or charcoal, and work
it around the roots. Keep shaded, humid, but
drier at the roots until new root tips grow. Do
not overpot.
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Prepared by the AOS Education Committee