The Orchid Show at the Garden has inspired me to try growing orchids at home. Can you offer some advice on where to start?
— Jose Alvarez, Highwood
Moth orchids (Phalaenopsis) are among the easiest orchids to care for in a home and are easy to find in shops and gardening centers. Moth orchids prefer a warm environment of 70 to 80 degrees Fahrenheit during the day and above 60 degrees at night. This is right around where most of us keep our homes. Moth orchids should not be kept at temperatures above 85 degrees or below 55 degrees. Phalaenopsis species and varieties do not require much light to grow well. They do best with indirect light, so avoid direct sunlight to help prevent leaf burn. Try a bright, east-facing window or even a west- or south-facing window as long as the light is indirect. A north-facing window may not provide enough light, so move your plant to another location if it does not do well there.
Moth orchids are typically grown in a bark mixture that includes sphagnum moss or other medium to help retain water. A pure bark medium can dry out very quickly, while a medium of pure sphagnum moss holds water. Monitor carefully to avoid overwatering your orchid. Repot orchids every two to three years in a fresh growing medium. The best time to repot is when you see new root growth — that way the new roots can quickly adjust to the new potting medium, and you are less likely to damage the delicate root tips. Use a medium-grade orchid bark mix for plants in 5-inch and larger pots. Feed the moth orchid with a dilute, water-soluble fertilizer a couple of times a month when you water it during the growing season. Stop fertilizing during winter months.
Water your moth orchid early in the morning with rain or distilled water as the mix approaches dryness. Try not to use water that has been softened with a water softener. Overwatering is a problem more often than underwatering. The planting medium must be allowed to dry out slightly between waterings but should not be left dry for extended periods. In general, water an orchid planted in bark once or twice a week and less frequently if it is planted in moss. Your home environment should affect the frequency of watering.
Orchids can bloom two to three times each year with flowers that can last for more than two months once the plants have reached a mature size. Often you can urge a second flowering from each spike with timely pruning. When the last flower of the spike fades, examine the spike, looking for small fleshy bumps or nodes. From the base of the spike, count out three nodes (count only the green fleshy nodes and ignore any that are dried out). Cut the spike 1 inch above the third node. If your plant is healthy, this process should wake up one or two of the nodes to produce a new spray of fresh blooms. From the top node, a new flower stem should emerge within a couple of months. If there is no response or the flower spike turns brown, cut it off near the base of the plant where it emerged.
For more plant advice, contact the Plant Information Service at the Chicago Botanic Garden at plantinfo@chicagobotanic.org. Tim Johnson is senior director of horticulture at the Chicago Botanic Garden.