Yard and Garden: Moth Orchids



AMES, Iowa – Moth orchids are great year-round, but they're especially well-suited for cold days when you're spending a lot of time indoors. Their elegant flowers will brighten tables and windowsills in your home for months at a time. Tips from horticulturists with Iowa State University Extension and Outreach will give growers confidence to enjoy the orchids’ exotic appearance.  To have other houseplant questions answered, contact Hortline at 515-294-3108 or email hortline@iastate.edu.

What would be good indoor location for a moth orchid? 

Moth orchids (Phalaenopsis spp.) are one of the easiest orchids to grow indoors. Moth orchids grow best in bright, indirect light. Direct sun may actually harm the foliage. Ideal sites are east- and north-facing windows. Plants in a south window will need to be shaded with a sheer curtain. Phalaenopsis orchids will not grow or flower well in poorly lit areas. Fluorescent lighting can be used to supplement natural lighting in poorly lit areas. Place the fluorescent fixture 6 to 8 inches above the plants. Keep the lights on for 12 to 16 hours each day. 

What temperatures are favorable for moth orchids? 

Moth orchids prefer daytime temperatures of 70 to 80 degrees Fahrenheit and nighttime temperatures of 60 to 70 F. Cool nighttime temperatures of 55 to 60 F in fall help initiate flower development. Avoid exposing plants to temperatures below 55 F. 

How often should a moth orchid be watered? 

Moth orchids like a bark medium that is kept evenly moist. Plants should be watered well and then allowed to dry slightly between waterings. Water moth orchids more frequently when plants are actively growing and during bloom. Plants are susceptible to root rots and death when watered too frequently. 

How often should I fertilize a moth orchid? 

Moth orchids are light feeders. Fertilize moth orchids with a water soluble orchid fertilizer or a general houseplant fertilizer (diluted to half-strength) once a month when plants are actively growing in spring and summer. 

Will a moth orchid tolerate a low relative humidity during the winter months? 

Phalaenopsis orchids require a relative humidity of 50 to 60 percent. Unfortunately, the humidity levels in most homes during the winter months are well below this range. Humidity levels indoors can be increased with a room humidifier or by placing the plant on a tray or saucer filled with pebbles and water. The bottom of the pot should be kept above the water line. The evaporation of water from the tray/saucer will increase the relative humidity in the vicinity of the orchid. 

How often should a moth orchid be repotted? 

Repot moth orchids every two to three years. A moth orchid needs repotting when the plant has outgrown its container and begun to spill out over the edge of the pot. The breakdown of the growing medium in the pot is another indication that the orchid needs repotting. Repot plants in spring after the blooms have faded. Use a coarse, fir bark based orchid potting medium.  

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PHOTO: Netted Phalenopsis, courtesy of Dennis Schrock, State Master Gardener Coordinator, Iowa State University