Culture
Winter hardy to USDA Zones 10-12. In St. Louis, phalaenopsis is grown in pots in a fir bark based medium with superior drainage. It prefers warm, humid, damp but not soggy conditions in shady locations (bright light with no sun). It serves as an excellent houseplant as long as basic growing conditions can be met. Best sites are on east window sills, but plants also grow well on well shaded south or west sills, with growing conditions that include (a) temperatures at 72-85°F in daytime and above 60°F at night (a temperature drop to 55°F at night in fall helps initiate flower spikes), (b) significant humidity (50-60% - set pot on moist gravel tray with the base of the pot NOT standing in water and mist in morning), (c) bright light but no direct sun, (d) good air movement (ceiling fan is ideal) and (d) a potting mix of coarse fir bark or orchid bark mix that facilitates circulation of air and water. Plants will tolerate some brief temperature extremes, but temperatures in excess of 95°F or below 55°F should be avoided. Water thoroughly with tepid water in mornings only. Place potted plants in a sink and allow water to flow freely through the potting medium and foliage. Water mature plants one time per week (more often in the heat of the summer) and allow the potting mix to dry slightly between waterings. In order to help prevent the onset of stem/root rots, plants should never stand in water, should never be watered at night and should never accumulate water on the crowns. Fertilize on a regular schedule by application (after watering) of a balanced fertilizer at the rate of twice monthly at half strength or weekly at quarter strength. Repot as needed (approximately every two years) in spring after blooms have faded or just as new leaves begin to appear using a coarse, fir bark based orchid potting medium. The flower stalk should be cut to a one-inch stub after the flowers have faded.
Noteworthy Characteristics
Phalaenopsis is a genus of around 45 species of mainly epiphytic orchids native to India, southern China, and Southeast Asia. Commonly called moth orchids, they are popular house plants that, with proper care, will flower repeatedly once per year (sometimes more often) with the flowers lasting for four months or more. They are mostly epiphytic (grow on trunks and branches of trees without taking water or nourishment therefrom), but are sometimes lithophytic (grow on rocks taking nourishment from the atmosphere). They have a monopodial growth habit and lack pseudobulbs. Showy flattened flowers (each 3-6” wide) appear in long sprays on arching stems in a range of colors including white, cream, light yellow and purple-pink. Plants of some varieties will grow to as much as 3’ tall when in bloom. Large leathery succulent leaves (to as much as 18”) are elliptic and come directly from the rootstock.
Genus name comes from the Greek words phalaina meaning "moth" and opsis meaning "like" for the flowers that look like moths.
Problems
Scale, mealy bugs, slugs and snails may appear. Root/stem rots. Bud blast (bud drop without blooming) has a number of possible causes including changes in temperature, humidity, moisture, fertilizer or location.
Uses
Potted plants for sunrooms and larger window sills. Plants may be taken outside in summer under trees, but never placed in direct afternoon sun.