A beautiful species! Here is the culture for you:
The most important cultural thing to remember is to grow C.dowiana so its roots dry quickly. For this reason, C. dowiana is either grown in clay pots that barely accommodate the plant and one new growth, or it is planted in hanging baskets.
Cattleya dowiana also likes to be kept dry when it is not actively growing. Be careful not to over water it during the cool winter months when it is dormant.
In its native habitat, C. dowiana grows at the tops of tall trees in the jungle where its roots dry out rapidly after a rain. It also has a dry resting period in the jungle in December and January. Ignoring C. dowiana’s need to dry out will cause the roots to rot and eventually the pseudobulbs will decay.
Cattleya dowiana requires lots of sun. Plenty of moving air from fans is beneficial, too. This helps keep its leaves cool and aids in drying its roots.
In the Northern Hemisphere, C. dowiana begins growing in early spring, flowers in mid- to late summer. After flowering it goes dormant until the following spring. It requires frequent watering when it is actively growing, but little water after flowering until it begins growing in the spring.
Fertilizer lightly during the active growing season.