Epiphytic orchids, those that grow upon a support, have modified aerial roots that can sometimes be a few meters long. In the older parts of the roots, a modified spongy epidermis, called a velamen, has the function of absorbing humidity. It is made of dead cells and can have a silvery-grey, white or brown appearance. In some orchids, the velamen includes spongy and fibrous bodies near the passage cells, called tilosomes.
If your Catasetum orchid leaves begin to yellow and drop off, do not despair; this deciduous orchid loses its leaves naturally during winter dormancy. There is much variation in appearance between Catasetum species, but one feature they all have in common is the trait of producing male or female flowers, which bear little resemblance to each other. The male flowers have an anatomical trigger that forcefully ejects pollen onto visiting bees.
Epidendrum orchids are among the oldest genera in the orchid taxonomy. Originally, this genus included all epiphytic orchids. As knowledge of the different types of orchids expanded, the classification became much more refined; for example, there are now some terrestrial species in the Epidendrum genus, and a great many other species have been moved to other genera. Still, over 1000 Epidendrum species exist. They are usually easy to grow, and most have tall canelike pseudobulbs that lean all over the place and frequently produce keikis. Fun orchids!
Once you develop more than a passing interest in orchids, you will quickly notice how diverse this exotic plant family is. Encompassing genera that yield both the vanilla you love to bake with and fragrances you love to wear, each flower has unique characteristics and care requirements. Compare your plants to some of the most commonly cultivated orchids to help you determine what type of orchid you are growing.
Disa is a genus of beautiful plants with rather triangular flowers, often red. They require VERY different care than other types of orchids, so it's easy to kill them if you don't know what you're doing. In particular, they like it wet and should never dry out. The best-known Disa is Disa uniflora, which in South Africa is known as the Pride of Table Mountain.
One of the most interesting things about growing any type of orchid is how they grow. Most of the houseplant orchids and even lady slipper orchids need good air flow around their roots. With indoor orchids, use an orchid potting mix that features some kind of blend of composted bark, expanded clay pellets, hardwood charcoal and peat moss or sand. The mix should create many air pockets for orchid roots to breathe.
Water thoroughly. When you do water, do it like you mean it. Different growers have different rules, but many professional growers turn on their sprinklers for 8 or more minutes. Successful home-growers sometimes dunk their plants, pots and all, into a bucket or sink of water. Some varieties, such as vandas, can be left floating in water for a surprisingly long time. The idea is to make sure the velamen is completely saturated. You want tiny droplets hanging on the roots after watering. This means the plant is completely hydrated.