Understanding the Catasetinae growth cycle is the key to successful culture. When the plants are in active growth, maintain a fairly constant root zone moisture and fertilize regularly to optimize new growth. When the plants are dormant little or no water is needed as the pseudobulbs store sufficient water and nutrients to survive their winter rest. Fred Clarke of Sunset Valley Orchids offers these recommendations.
Early Season. Catasetums begin their new growth cycle in winter to early spring. Once you see new growth, repot your plants into new medium. Last year's roots seem to deteriorate during dormancy and are not as effective as the new roots at taking water and nutrients. Whether or not you repot, do not water your plant until the new growth has well developed new roots. Your roots should be 3 to 5 inches long, so for the sake of simplicity, do not water until your new top growth is 3 to 5 inches tall. This cannot be emphasized enough. Do not water until the new growth has become well established.
Mid-Season. New roots are established and the plants are rapidly developing their new pseudobulbs. The growth spurt during this 3 to 4 month period is surprising, often the plants will double in size. To keep pace with their growth rate, the plants require constant moisture and regular fertilization. Normally you will water 2 or 3 times a week. A balanced fertilizer at full strength is suitable for this rapid growth or you can top dress with a controlled release fertilizer and apply water soluble fertilizers at a dilute rate, say 1/4 tsp/gal. Light levels at or above those suggested for Cattleyas will help insure strong good growth and flowering. The fruits of your labor will begin to pay off as the flowering season begins.
Late Season. In the late autumn the plants will begin to enter the dormancy phase, caused by the maturity of the pseudobulb, shorter day length, cooler day/night temperatures and a reduction of root zone moisture. The first signals you will observe on your plants are yellowing and browning off of the leaves. As a general rule, this will happen by mid-November, at which time you will stop fertilizing them and reduce watering by half. When all the leaves have dropped or by the end of December, stop watering the plants. Watering during dormancy should only be done it the plant bulbs shrivel severely. Usually a single irrigation is sufficient to restore the bulbs.