The profuse blossoms fade and fall from the flower spike, leaving your moth orchid (Phalaenopsis spp.) bare. Phalaenopsis are the lovely flowering orchids found in many stores and florist shops. While other orchids may be available, Phalaenopsis is the easiest to locate, grow and rebloom. Hardy in U.S. Department of Agriculture plant hardiness zones 10 through 12, it thrives indoors in winter and enjoys shady outdoor locations in summer.
Phalaenopsis, Odontoglossum and Zygopetalum are among the orchid species that are stimulated to rebloom when temperatures drop 10 to 15 degrees Fahrenheit at night. The ideal temperatures for these orchids are 75 to 85 degrees F during the day and 60 to 65 degrees F at night. If the orchid is a houseplant, when outside temperatures drop at night, open a window to pull in the cooler night air. Monitor night temperatures -- the orchid should not be exposed to temperatures below 58 degrees F.
Phalaenopsis, like other orchids, prefers bright, filtered light from an east- or west-facing window. In winter, you can use a full-spectrum grow light to provide additional light to help stimulate growth and new flower spike development. If the orchid's leaves are dark green, it's not receiving enough light. The leaves should be a light greenish-yellow. However, avoid placing the orchid in direct sun; the leaves easily burn in sunlight.
Orchids require regular watering, generally once a week when the potting mix is dry. Place the orchid pot in the sink and fill the pot with water. Allow the water to drain completely from the potting mix, and then repeat twice to ensure that the bark or other medium is moist. Orchids also require higher humidity than most homes provide. A tray filled with pebbles and water under the orchid pot helps raise the humidity, while a cool steam vaporizer adds additional moisture to the air around the orchid.
To encourage the orchid to rebloom, it needs regular feeding. Feed the plant with a one-quarter strength 20-20-20 fertilizer solution every week, immediately after watering. Mix 1/4 teaspoon liquid fertilizer with 1 gallon of water, and pour the solution over the potting mix until it drains from the bottom of the pot. The American Orchid Society recommends avoiding fertilizers formulated with urea, which may burn the orchid's roots.
Phalaenopsis reblooms from the flower spike, but the second blooming may have fewer, smaller flowers. Some gardeners trim the flower spike to one or two nodes, approximately 1 to 2 inches long. Others recommend trimming the flower spike to the base of the plant. Always sterilize your pruners before and after cutting the flower spike to prevent the spread of fungi or disease, using a solution made of equal parts water and rubbing alcohol.
Orchids vary when reblooming. Some species may not bloom again until spring, while Phalaenopsis may begin developing new flower spikes from the nodes left on the trimmed flower spike and bloom again in eight to 12 weeks. Once the orchid blooms, the flowers linger for four months or more.