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East Everglades
Orchid Society
15220 SW 232 St.
Miami, FL 33170
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Catasetum Culture
by Bert Pressman
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 The proper culture of Catasetums requires recognition of two distinct growth phases: 1, Active growth, which culminates with the onset of dormancy, as manifested by the withering and loss of foliage; 2, Dormancy , which lasts 6-12 weeks and culminates with the onset of new growth. At the beginning of active growth, watering is particularly critical because of susceptibility of Catasetums to fungal and bacterial disease, or, in the old fashioned vernacular, "rot." Some plants begin to flower as soon as new growth resumes; others flower upon maturation of the new pseudobulbs, occasionally as late as the onset of dormancy, sometimes even during dormancy. During active growth, the principal danger to Catasetums is damage by snails and insects, particularly spider mites. Exposure of plants to insects can be minimized by enclosing the growing area with 30%-70% nylon screen, which also provides optimal screening. Catasetums tolerate a wide light range, from Vanda light to Cattleya light; they may be watered freely during active growth, but water must be rigorously curtailed as dormancy approaches. During dormancy, infrequent light watering may discourage pseudobulb shriveling.
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|  REPOTTING
The best time to repot Catasetums is in the spring, when new growth resumes as evidenced by the showing of "eyes" at the base of old bulbs.. Pots and potting medium are the choice of the grower. Plastic pots are advised for dry environments and porous clay pots for humid ones. The potting medium may be chosen from locally available materials and should be chosen to assure good aeration and accessibility to nutrition. Some commercial nurseries use a mixture of fir bark, charcoal and perlite or sponge rock. An alternative I use is: ½ small Aliflor, 1/3 short fiber sphagnum and 1/6 coarse perlite. Leaving the old mix in place during dormancy protects against bulb shriveling. When the new eyes sprout to about 1 inch,, plants may be removed from the old medium, all old roots and dead bulbs removed, care being taken to preserve the new green, roots of the new growths, and then repotted. When I am lazy, I occasionally leave them in the old mix for a second year.
WATERING
With the advent of new growth, watering is resumed in the following manner:
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- At first, water only sparingly, taking care that water does not remain within the new growth longer than six hours. Do not water on days of high humidity but water the potting medium directly whenever it seems dry.
- When new growth reaches 3-10 cm, gradually increase and maintain heavy watering throughout active growth until the onset of dormancy. During active growth Catasetums require lots of water.
- When dormancy commences in late fall, gradually reduce the quantity and frequency of watering; as leaf fall progresses, halt watering completely and permit the medium to dry out. Dormant plants may be left outdoors during our winter; when dormant they seem to tolerate low temperatures above freezing, and an occasional winter rain may be beneficial in keeping the bulbs from shrinking excessively.
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 FERTILIZING
Since adult catasetums probably grow faster than any other orchids, they require heavy fertilization during active growth. Begin fertilizing with the second watering after the end of dormancy, using a balanced fertilizer such as 10-10-10 or 20-20-20. One can use 1/3rd the recommended concentration, that is 1 tsp/gal, at each subsequent watering. Another way of fertilizing continuously is to add a slow release fertilizer such as OSMOCOTE 14-14-14, about 1 tsp/pot, and fertilize with 20-20-20, weekly, along with the rest of your orchids. There is increased danger of rot if fertilization is started before the new growth appears.
CATASETUM CULTURE REVISITED
(October 2002)
It is now fall, the most glorious time of the year for a Catasetum Buff. Here are some last minute thoughts to append to my previous Catasetum Cultural Advisory.
When I first started to grow Catasetums, they bloomed predominately male, as most others experience.
The party line is that high light intensity encourages female flowers. I grow under 35% shade, and I have always gotten a reasonable percentage of female flowers, in the order of 1/3, particularly around June. This year however, the first 15 Catasetums and Cycnoches to bloom were all female; as the season progressed they reverted to predominately male. I grow enough Catasetinae so that my observations are statistically significant, but darned if I could figure out what was different this year.
Collectors report that, in the field, Catasetums are often found growing on the stumps of dead trees possibly deriving nutrients from the wood. Accordingly this year I added 20% wood chips [in Miami, JW Dawson Co, 3739 NW 43 rd St.], the rest of the mix 50% small Aliflor, 20% milled sphagnum and 10% coarse perlite. Perhaps the sawdust had something to do with the early female predomination.
 Starting in October, Catasetum leaves begin to wilt and rot. Although my Catasetums are deployed to get high light early in the year, as their lush foliage grows they begin to shade each other. I remove the wilted leaves daily in order to increase the availability of light to the unwilted leaves.
Do Catasetinae lose their leaves because they enter dormancy, or because watering is decreased? I believe the former, and therefore continued watering in the fall does not retard leaf drop. Accordingly, I remove my Catasetinae from my overhead sprinkler area as they become leafless, which retards pseudobulb rot. Occasionally a Catasetum fails to lose its leaves, especially during warm winters, and presumably can be watered all year long. Dry, dormant Catasetums will tolerate temperatures in the low 40's.
A word about the culture of other genera of the Catasetum alliance. Clowesias behave much like Catasetums except that each flower is bisexual. Their bulbs are the most resistant to rot. Cycnoches ["Swansneck" orchids] are sexually dimorphic like Catasetums and are a bit more susceptible to rot, so be careful watering them in the fall. Mormodes ["Goblin" orchids] are bisexual with twisted columns and are the most susceptible to rot. The remaining genus, Dressleria, is seldom grown. Its flowers are bisexual, resemble white frog faces, but do not go dormant and should be grown shady and wet all year long. Its bulbs are not particularly prone to rot. |
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