Light is the most important factor in growing and flowering
cattleyas, whether in a greenhouse or in the home. Bright light to some sun
should be given to the plants, with no direct sun in the middle of the day.
This means an east, shaded south (as with a sheer curtain) or west window in
the home, and 50 to 70 percent full sun in a greenhouse (3,000 to 5,000
foot-candles). Leaves should be a medium green color, pseudobulbs erect and
requiring no staking.
Temperatures should be 55 to 60 F at night and 70 to 85 F during
the day. Seedlings should have night temperatures five to 10 degrees higher. A
15- to 20-degree 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.
Water should be provided in two ways: in the pot by
watering and in the air as humidity. Watering in the container is dictated by
many criteria: size and type of the vessel, temperature, light, etc. Mature
cattleyas need to dry out thoroughly before being watered again. Seedlings need
more constant moisture. Compare the weight of a dry pot of the same size and
type of mix; it can indicate if a plant needs water by the relative weight -
light means dry, heavy means wet. 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 water softened by the
addition of salts.
Humidity should be 50 to 80 percent for cattleyas. This can
be provided in the home by placing the plants on trays of gravel, only
partially filled with water so that the plants do not sit in the water. Air
should always be moving around the plants to prevent fungal or bacterial
disease, especially if high humidity or cool temperatures exist. In the
greenhouse, the humidity is best increased by use of a humidifier. Evaporative
cooling increases humidity while cooling the air.
Fertilize on a regular schedule. In fir bark, a
high-nitrogen (such as 30-10-10) formulation, or a similar proportion, is used.
Otherwise, use a balanced fertilizer. When in active growth, plants need
fertilizer at least every two weeks, and when not actively growing, once a
month. Fertilizer can also be applied with every watering at one-quarter the
recommended dilution. Thorough flushing with clear water every month is
recommended to prevent the buildup of fertilizer salts.
Potting is necessary when the rhizome of the plants
protrudes over the edge of the pot or the potting medium starts to break down
and drain poorly (usually after two to three years). It is best to repot just
before new roots sprout from the rhizome, after flowering or in the spring.
Mature cattleyas are usually potted in coarser potting material than are seedlings.
Until a plant has at least six mature pseudobulbs, it generally should be put
into a larger pot and not divided. If dividing a plant, three to five
pseudobulbs per division are required. Select a pot that will allow for
approximately two years of growth before crowding the pot. Pile mix against one
side of the pot and cut off any dead roots. Spread the firm, live roots over
the pile, with the cut rhizome against the side of the pot. Fill the pot with
medium, working it around the roots. Pack firmly and stake if necessary. Keep
the plant humid, shaded and dry at the roots until new root growth is seen.