Previously published in Houston Happenings, MONTH 2003.
|On the north end of our plant tables at each
society meeting we always see several Vandas. This article will deal
with the culture of commonly grown Vandas and Vanda alliance orchids
often observed in the Houston area. Species of Vanda, Ascocentrum,
Aerides, Renanthera, Arachnis, to mention a few, and their hybrids are
in this group.
Water and Fertilizer
Most growers in the Houston area underwater their
Vandas. They are difficult to over-water. Most or all need to be grown
in open baskets or on plaques. These plants need daily water for ten to
fifteen minutes minimum or several waterings during each day. Two
successful growers immediately pop into mind. One rings a greenhouse
alarm to clear the growing area of people. The water sprinklers come on
and water for ten to fifteen minutes with large volumes of water. The
roots will turn a solid, dark green indicating that they have absorbed
their limit of water. The baskets hang seven foot in the air and the
roots of all the plants almost touch the rock-covered ground. The plants
are very healthy and well grown.
Most growers cannot afford to run large volumes of
water over plants for ten to fifteen minutes for several reasons. Our
yards would flood and water would run into the street. A second reason
is the cost of water. Even though we have very low water prices in the
Houston area with no limits on use, the cost would be noticed on the
The second grower uses a more practical method. He
has a timer that opens and sprays his orchids two to three minutes three
So, why do Vandas require so much water, where as
other orchids can be very healthy with much less. Vandas have roots that
take in water and fertilizer at a very slow rate. Also the roots are
large and present less surface area. Third, many of the roots are
hanging in empty air and not attached to media. Maximum absorption
occurs where the root contacts and adheres to media of some type. So
provide twice as much fertilizer and extra water.
Do not pot Vandas. The roots are limited, large,
stiff and will break and tear when you remove the plant during
repotting. Vandas tend to stop growing and flowering when theirs roots
are repotted or disturbed. If damaged, roots will take many months or
years to resume healthy, productive growth. All orchid roots absorb the
maximum amount of water and nutrients where the roots attach to media.
Time is necessary for the roots to grow again and attach. The best
solution is to remove all rotten or loose basket wood and set the plant
and remaining basket into a larger wooden basket. Incidentally, there
are new black, plastic baskets marketed as Vanda baskets. We will have
to grow orchids in a few to determine how well they grow Vandas.
Most Vandas, except Vanda coerulea, grow in hot,
bright tropical climates. Provide more light than Cattleyas but do not
give excessive amounts. Vanda sanderiana, an ancestor in most of our
Vandas, is from the island of Mindanao in the Philippines 5 degrees
above the equator. They grow in the tops of hardwood trees. The sun
shines during the morning with a rain in the afternoon and occasional
cloud cover. About sixty to seventy percent of the time there is cloud
cover. Direct light lasts for short periods of time. The humidity
averages eighty to eighty one percent.
Thailand, Florida and parts of Hawaii grow the
best Vandas because of constant, year round temperature and light.
Thailand growers use slat houses with one inch slats and one inch spaces
to block out of the light. Hawaiian and Florida growers use shade cloth
to accomplish the same growing conditions. Houston has the same light
conditions except during the months of December, January and February.
These months can be the most troubling. We need to remove shade cloth
and provide as much light as possible during the many cloudy, overcast
days. However, occasional cold fronts blow through clearing out the sky
providing very bright direct sunlight. Burning often occurs on these
bright, cold days, because our greenhouses are closed and air movement
is below normal.
Terete leafed types will do well in direct
sunlight, but the Rhynchostylis, Vandopsis and Neofinetia species and
some hybrids need lower Cattleya light.
Vandas will take four to eight years to mature and
produce large flowers. If you do not wish to wait this long buy
ascocendas, which are hybrids between Vandas and ascocentrums.
Ascocentrums flower early, around three years, with many small flowers
on small, charming plants. The hybrids are a compromise with fewer,
larger, earlier flowers.
With good culture, most flower twice each year. A few flower when growths are mature and healthy. Others will flower continuously if excellent culture is observed. The flower inflorescences will emerge between the fourth and fifth leaf from the top. Vanda coerulea hybrids display flowers well above the foliage, tend to have blue, tesselated flowers and grow less tropical. Many inflorescences need support and grooming, as they are quite heavy. If you like to water and fertilize orchids, perhaps Vandas are for you.