While they are considered a great orchid for beginners, some people have trouble with Dendrobium phalaenopsis hybrids. With the hybrids, think more of everything—more light, more water, and more fertilizer.
The plants are robust growers that send up at least one new upright cane every year from creeping rhizomes. Don’t cut off old canes, as they store nutrients and water to keep the plant healthy. Older canes will sometimes flower or produce tiny plantlets, called keikis, that can be potted up on their own after they develop roots.
You can find a wide range in the color, size, and shape of the blooms. The long-lasting sprays of flowers remain in bloom for six to eight weeks. You can use the sprays to use as cut flowers for arrangements. These bloom several times throughout the year, depending on conditions. To help provoke a flower spike, slightly drop the water and nighttime temperature.
These plants like strong, natural sunlight. They will grow in lower-light conditions, but it is unlikely the plant will bloom well. The appearance of keikis often means the plant isn’t getting enough light. On the other hand, if you see yellow leaves you may have given the plant too much direct sunlight.
Orchids don’t grow in soil, but rather in a special mixture that mimics their environment in the wild. Purchase a commercial orchid potting medium, which contains peat moss, perlite or fir bark, or make your own that has these ingredients in it. Make sure that the “soil” has aeration and is well-draining, so the roots aren’t left in moisture for a lengthy period of time.
During the growing season, dendrobiums like high humidity and lots of water. As with all orchids, the frequency of watering depends on your growing conditions, but at least weekly is a good idea during the summer. Don’t leave them in a tray of water as that can rot the roots.2 After the growing season, cut water back somewhat (maybe every 10 days), but do not suspend watering.
Feed heavily during the growing season with a weak fertilizer solution containing lots of nitrogen, or use a balanced fertilizer like Peters 20-20-20 at quarter-strength with every watering. At the end of the growing season, reduce fertilizer by about half to help provoke a better bloom.
Temperature and Humidity
There are considered warm-house plants by growers, meaning they favor conditions in a warm greenhouse. The temperature for these plants should be above 60 degrees Fahrenheit at all times. Although experience has shown they can withstand a few nights down to 50 degrees Fahrenheit, this should be avoided if possible. A slight drop in nighttime temperature will often stimulate a bloom.