Orchid Care: Cattleya
Cattleyas are among the most commonly grown orchids. The flowers of cattleyas and their related hybrids come in a wide range of colors. Culture varies only slightly among most of these groups; this cultural information is intended as a general guide to "standard" cattleya culture.
Like most other cultivated orchids, cattleyas are epiphytes, or air-plants. They have developed water-storage organs called pseudobulbs and have large, fleshy roots covered with a spongy, water-retentive velamen. They should be potted in very porous, free-draining media, the most popular being fir bark; other media are shredded tree-fern fiber, various types of rock and processed coconut fiber.
TEMPERATURE Recommended temperatures are 55° to 60°F at night and 70° to 85°F during the day. Seedlings should have night temperatures 5° to 10° higher. A 10° to 20° differential between day and night is recommended, especially for mature plants. Higher day temperatures can be tolerated (up to 95°F), if humidity, air circulation and shading are increased.
LIGHT is one if the most important factors in growing and blooming cattleyas, whether in a greenhouse or in a home. Bright filtered light to some sun must be given to the plants, but no direct sun in the middle of the day. This means an east, shaded-south or west (as with a sheer curtain) window in the home, and 30% to 50% of full sun in a greenhouse. Leaves should be a medium green color. A good test is if the leaves are weak and turn dark green or yellow green, the plant is getting too little or too much direct sun.
WATER should be provided in two ways: In the pot by watering and in the air by humidity. Watering in the pot is dictated by many criteria: size and type of pot, temperature, light, etc. Mature cattleyas need to dry out thoroughly before being watered again. Seedlings need slightly more constant moisture. Compare the weight of a dry pot of the same size and type of medium; it can indicate if a plant needs water. A freshly sharpened pencil inserted in the potting medium can be an indicator of moisture. If in doubt, it’s best to wait a day or two until watering. Plants in active growth need more water than plants that are resting. Water below 50°F may injure plants, as will softened water.
HUMIDITY Cattleyas need 50% to 80% relative humidity. This can be provided in the home by placing the plants on trays of gravel, partially filled with water so that the plants stand above the water. Misting the plants in the morning only is helpful in dry climates. Air should always be moving around the plants to prevent fungal or bacterial disease, especially if high humidity and/or cool temperatures exist. In the greenhouse the humidity can be increased by wetting the floor. Evaporative cooling increases humidity while cooling the air.
FERTILIZER During the summer, fertilize twice a month using a 30-10-10 formulation and switch to a 10-30-20 in the fall until flower spikes appear. In the winter, feed once a month with a 20-20-20 fertilizer. Ideally, it is best to feed each week with half the recommended dose since cattleyas are used to consistent nutrients in the wild.