The Vanda Alliance, originating in tropical Asia, is made up mostly of full-sun-growing orchids with colourful flowers
Light is one of the most 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. Be careful to aclimatize plants to avoid burn.
Vandas must be kept warm; a minimum night temperature of 15°C is recommended. Optimum temperatures are 15°C to 21°C at night,
and a maximum of 35°C 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.
Moisture 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.
80 percent humidity 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.
Use 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.
Transplant 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.
Information provided by The American Orchid Society