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Cattleyas for the Beginner - 1

Cattleya Diagram
b=bud; c=column; ds=dorsal sepal;
e=growth eye; l=lip; lf=leaf;
ls=lateral sepal; p=petal; ps=pseudobulb;
r=root; sb=sheathing bract; sh=sheath

 

To many people the term Cattleya is synonymous with orchids. For a long period, a Cattleya corsage was a prerequisite for any special occasion and as a result the Cattleya has often been called the Queen of Orchids. While no longer the reigning queen of the orchid floral industry it is difficult not to be impressed by a well-flowered Cattleya. No longer limited to white and various shades of lavender and purple, high quality flowers are available in the entire color spectrum (except true blue) and in a wide range of plant sizes. Most Cattleyas and their relatives are easy to grow. With reasonable care, they can be grown anywhere in the world. Their requirements are few and are summarized below. For the meanings of terms which refer to parts of the plant and flowers, see the accompanying plate.

Cultural Requirements for Blooming-Size Cattleyas

An adult plant is one mature enough to flower. It will be about four to seven years from seed, if is has never flowered before, or older if it has flowered in the past. With proper care, a Cattleya plant can be grown on indefinitely and can be flowered year after year. Proper care depends on a few basic factors, each of them influenced by the others. They are: 1) light and shade; 2) temperature; 3) air movement; 4) humidity; 5) watering; 6) potting and potting medium; 7) feeding. These environmental factors vary from place to place, and each plant will differ in its requirements according to its kind and, to a lesser degree, its individual condition. The essence of good growing is in achieving a happy balance of all factors in relationship to each plant. This is not too difficult, but it demands knowledge, understanding and careful observation on the part of the grower.

copyright Greg Allikas - orchidworks.com

Light and shading - To grow well and to flower consistently, cattleyas require a good amount of light, preferably in the range from 2,000 to 3,000 foot-candles (about 65-70% shade), although they will tolerate a great deal more light if it is accompanied by sufficient humidity and air movement to keep the leaf-temperature down. Natural light varies according to the weather, the season, the time of day and geographical location. Therefore, for more northern parts of the country, a “good amount of light” will mean as much light as possible in the late fall and winter, light shade in late winter and early spring, increasing to a maximum in late spring and summer and decreasing in the fall. For the more southern areas of the United States, such as South Florida, Southern California and Hawaii, shading will be necessary all year round. Shading can be an opaque coating painted or sprayed on the outside of a glass greenhouse, a solid material such as lath, commercially available shade cloth, translucent to semi-translucent material such as plastic sheeting or fiberglass panels and, for windowsill culture, a light shear curtain.

copyright Greg Allikas - orchidworks.com
Note dark green leaf color of plant grown
under too little light to flower.

Light varies according to the time of day. Early morning sun, accompanied by high humidity and low temperature, is especially important. Shading should be heaviest from midday through the late afternoon, especially if plants are grown in windowsills. Afternoon sunlight coming through west-facing windows can be extremely hot and, without adequate air movement and humidity, damaging to your plants.

Cattleyas receiving too little light can be recognized by the dark rich green color of their foliage and failure to flower. Cattleyas receiving a proper balance of light, humidity and temperature will have rather light yellow-green leaves. Too much light will turn the leaves more yellow than green, give them a dull appearance, or will burn black areas on the upper surfaces of the leaves facing toward the sun.

Temperature - Although Cattleyas come from the tropics where the sunlight is hot and intense, most species are found at fairly high altitudes where the air is cool and moist, particularly in the morning and at night. Thus in home or greenhouse culture, the goal is to provide maximum sunlight without excessive temperature. In winter, the daytime temperature should range from about 60F to 70F, the night temperature being set for a minimum of about 55F. In the summer, a night temperature of 60F to 65F is desirable, while the day temperature ideally should range from 65F to 75F, but an upper limit of 85F is more realistic. Cattleyas will withstand higher temperatures, even over 100F but prolonged exposure will prove harmful. At temperatures above the low 90'sF the plants cannot transport calcium within their tissues. Under these conditions, the plants are susceptible to dieback of the leaf tips on the young developing growths. Mature leaves are not affected making the problem easy to diagnose. High humidity and good air movement will help to compensate for excessive day temperature.

Air Movement - In climates where natural humidity is high, simple ventilation is practical, but in many areas, where natural humidity is low and temperature is high, ventilation can be destructive by draining away humidity in the growing area, drying out the plants and retarding growth. In these climates ultrasonic humidifiers (also called cool-mist humidifiers) and fans set a low speeds are a better solution and in greenhouses evaporative coolers. Fans should run continuously since air movement at night is just as important, providing a light buoyant atmosphere. The small greenhouse, especially, profits from the installation of good fans or blowers, strategically placed to circulate the air throughout the house. Humidity is maintained; the moving air keeps leaf temperature down and helps to avoid the stratification of cool moist air below the benches and warm dry air above, where the plants are. “Dead spots” are minimized and, equally important, damp stagnant areas - breeding place for disease - are eliminated. One to several fans, the number and size depending on the size and structure of the greenhouse, will more than repay their cost. If plants are grown in the home, overhead paddle fans set on the lowest possible speed or a small oscillating fan set facing away from the plants will accomplish the same goal.

When ventilators are opened, care should be taken to avoid drafts, for most cattleyas can be damaged by sudden changes in temperature. This is especially important in the winter or on cold windy days.

Humidity - Cattleyas do best when humidity ranges from 40% to 70%. Humidity as a rule is highest at night and lowest during the afternoon peak of sunlight and warmth. Therefore, except in areas where natural humidity is quite high, or during cold, cloudy or rainy weather, it is important to add moisture to the growing environment, especially during the day. This can be accomplished in a number of ways. For small collections grown under lights, humidity trays may be sufficient. These trays are nothing more than a water-holding tray filled with small gravel (aquarium gravel works well). The gravel-filled trays are filled with water to a level just below the surface. To prevent plants sitting on constantly wet gravel the plants are placed on small saucers or pieces of plastic or metal grid placed on top of the trays. Greenhouses should be damped down in the morning, and again during the day if necessary and possible. A mist spray of the foliage is useful in bright hot weather. In a small greenhouse this may be needed several times a day. A good humidifier, properly connected to both a humidistat and a thermostat, is an almost indispensable automatic device for the greenhouse, particularly if the greenhouse must be left unattended during daylight hours.

In cold dark weather, the greenhouse should be drier. Reduce or dispense with damping down, spraying and humidification, unless artificial heat has already dried out the greenhouse.

Where natural humidity is high or where humidification maintains a high degree of humidity, increased air movement is essential to prevent stagnant air and the development of diseases. Good ventilation or the use of fans is recommended (see “Air Movement” above.)

copyright Greg Allikas - orchidworks.com
Too little water has dehydrated this plant.

Watering - Improper watering, both under- and over-, leads to the death of more orchids, including Cattleyas, than any other single cause. There are two aspects of proper watering to consider: when and how. Simply summarized, cattleyas should be watered only after the potting medium has become “dry.” Frequency of watering will vary. Once a week is a good base to begin, remembering that some factors will speed up drying of the potting medium, others will slow it down. A lot of sunshine, heat, good air movement, active growth, a large plant in a small pot, low humidity, the type of potting medium (such as bark, gravel, tree fern chunks, etc.), windy weather and the like all contribute to faster drying and, consequently, increased frequency of water. Conversely, high humidity, dark, cold, cloudy or rainy weather, large pots, inactive plants (that is, not in active growth), tightly packed potting medium, little air movement and similar circumstances will slow the process of drying and hence decrease the frequency of watering. Note that some of these factors affect the entire collection of plants, other affect only certain individual plants. Watch each plant carefully, consider each by itself. Each beginner must learn for themselves, but remember that plants will recover much more rapidly from under-watering and it is best to err on the dry side, following the rule, when in doubt, don't water.

Many beginning grows soak their plants in a bucket of water. While this may at first seem to be a good way of making sure the potting medium gets thoroughly wet, it is actually not a good practice. Should one of the plants have a disease or insect infestation, all those soaked in the same water after it may well become infected. For small collections it is much better to place the plants in the sink and carefully flood with water until the medium is thoroughly wet, being careful not to wash the medium out of the pot. Take time to let the water run copiously from the bottom of the pot, leaching away accumulated fertilizers or minerals from the water.

Potting media - There are a bewildering array of potting media available in which Cattleyas can, and are, grown to perfection; chopped bark, tree fern fiber, coconut husk chips, gravel or lava rock and even sphagnum moss. The most common potting media are still based more or less on chopped fir bark although more open media like tree fern fiber or inorganic media like expanded clay pellets and lava rock may be a better choices in very humid hot areas of the country. The choice is predominantly a personal one and based on whatever gives good results for the grower.

copyright Greg Allikas - orchidworks.com

 

To pot a Cattleya plant, it should first be cleaned of old roots, decayed medium and debris. The new potting medium should be moistened before use if possible. This is again more or less a personal choice but soaking the potting medium before use helps to reduce the amount of dust (bark and tree-fern based) and it's easier for beginners to determine when to water when they start with moist media. Select a pot of sufficient size to allow for two years of growth (avoid over potting!). For added drainage broken pots (crocking), gravel or even Styrofoam peanuts can be used to fill up to one-third of the pot (if using slotted clay “orchid pots” this added drainage is unnecessary) . Place plant so the bottom of the rhizome is about ½ inch below the pot rim with the oldest part of the plant against the pot rim. Pack potting medium evenly and firmly around roots up to side of rhizome, being sure there are no loose spots or holes are in the medium. Stake and tie plant as needed.

Potting as a rule should be done when the plant begins to throw out roots at the base of the new growth, or just after the new growth begins. For most cattleyas, the time of repotting is not as important if media easily removed from the roots is used, and some growers repot throughout the year as time is available. There are exceptions however. Many of the bifoliate (two-leaves per pseudobulb) cattleyas resent repotting unless new roots are being formed and, if at all possible, these should not be disturbed unless new growth and new roots are beginning.

Feeding - Cattleyas, like other orchids, are capable of growing (and even flowering) for several years without fertilizer however they will do better with an adequate nutrient regimen. Historically, for cattleyas in a bark medium, a high nitrogen formula like 30-10-10, has been recommended but current research indicates that this high nitrogen is unnecessary and may well hasten the decomposition of the potting medium especially in hot humid areas of the country. A better choice would be a urea-free lower nitrogen formulation such as 10-10-10 or 13-13-13 used in dilute solution (1/4 to ½ of the recommended strength) during active growth and in bright weather. To avoid the accumulation of salt buildup in the potting medium, the pots should be flushed with plain water between fertilizer applications.

Overfeeding, in cattleyas, can lead to loss of roots and consequent death of the plant. To a lesser degree, when feeding a well-rooted plant, overfeeding can result in the production of vegetative growth instead of flowers, sometimes resulting in blind sheaths. In feeding, it is better to err on the side of too little than on the side of too much.