LIKE most of the large-flowered Cattleya species, Cattleya rex is relatively easy to grow. It will send out a new lead in late winter or early spring in the United States and complete the growth from late May to late June. Buds will appear in the sheath before the growth is completed and the plant should be in flower by mid-July to early August. After flowering, Cattleya rex will rest until it begins growing again in late winter.
Catileya rex seems to grow best in smaller-size pots that will allow no more than one year’s new growth. After they flower, I treat them like C. dowiana, keeping the plants as dry as possible during the autumn and winter months when they are dormant. Like Cattleya dowiana, Cattleya rex benefits from lots of sun during the winter months, and the more sun it receives, the more flowers it will produce. I grow my Cattleya rex in my intermediate house which ranges from 60 F at night to 85 F during the day.
Cattleya rex will usually send out a new flush of roots about the time it begins new growth and the best time to repot it is when this flush of roots appears. Under greenhouse conditions, Cattleya rex will usually produce a 10″or I 2″ tall pseudobulb, and four to six flowers on a flower spike. Unlike C. dowiana, which often lasts only a week or so in flower, Cattleya rex flowers will normally last three weeks or more.
Some people have described Cattleya rex as difficult to establish, but I have not found this to be true. When I acquire Cattleya rex plants, even imported plants, I wash off all the old medium and immediately pot them in sphagnum moss in the smallest-possible pots they will fit into. I do not allow any room for the plant to make a new growth since the purpose here is to encourage the plants to root, not grow. Once they are well-rooted in the small pots, the whole rootball is eased out of the small pot and moved into the next-size pot, one that will allow room for one new growth. At this point, you can add your standard medium in front of the sphagnum rootball and the plant should grow normally. When using sphagnum, it is important not to pack it tightly so there is a good air exchange to stimulate root growth. You should also avoid using more than a 4-inch pot so the sphagnum will not stay too wet too long. If you must go to a 5-inch pot because of the size of the plant, you will have to take care in watering the sphagnum so it will not stay too wet. Clay pots are preferred over plastic pots because they allow a better air exchange with the medium. — A.A. Chadwick.
Reprinted with the permission of the American Orchid Society. “Orchids”, September 2000