AMES, Iowa — Amaryllis are popular flowering bulbs grown indoors during the winter months. Single-flowering, double flowering, and miniature amaryllis varieties (cultivars) are available. The spectacular, trumpet-shaped blooms are available in many colors including red, pink, orange, salmon, white and bicolors. To find answers to other houseplant questions visit the Iowa State University Extension and Outreach Yard and Garden FAQ webpage at https://expert-hort.sws.iastate.edu/faq or contact Hortline at 515-294-3108 or firstname.lastname@example.org.
Some individuals discard the amaryllis after flowering. However, it is possible to save the amaryllis and force it to flower on an annual basis. The key to successful re-flowering is proper care.
After the flowers fade, cut off the flower stalk with a sharp knife. Make the cut 1 to 2 inches above the bulb. Don’t damage the foliage. In order for the bulb to bloom again next season, the plant must replenish its depleted food reserves. The strap-like leaves manufacture food for the plant. Place the plant in a sunny window and water when the soil surface is nearly dry. Fertilize every two to four 4 weeks with a water-soluble houseplant fertilizer.
The amaryllis can be moved outdoors in late May. Harden or acclimate the plant to the outdoors by initially placing it in a shady, protected area. After two or three days, gradually expose the amaryllis to longer periods of direct sun. Once hardened, select a site in partial to full sun. Dig a hole and set the pot into the ground. Outdoors, continue to water the plant during dry weather. Also, continue to fertilize the amaryllis once or twice a month through July. Bring the plant indoors in mid-September. Plants left indoors should be kept in a sunny window.
In order to bloom, amaryllis bulbs must be exposed to temperatures of 50 to 55 degrees Fahrenheit for a minimum of eight to 10 weeks. This can be accomplished by inducing the plant to go dormant and then storing the dormant bulb at a temperature of 50 to 55 F. To induce dormancy, place the plant in a cool, semi-dark location in late September and withhold water. Cut off the foliage when the leaves turn brown. Then place the dormant bulb in a 50 to 55 F location for at least eight to 10 weeks. After the cool requirement has been met, start the growth cycle again by watering the bulb and placing it in a well-lit, 70 to 75 F location. Keep the potting soil moist, but not wet, until growth appears. The other option is to place the plant in a well-lit, 50 to 55 F location in fall.
Maintain the amaryllis as a green plant from fall to mid-winter. After the cool requirement has been met, move the plant to a warmer (70 to 75 F) location.
The amaryllis may not have been able to store adequate food reserves in its bulb over the spring and summer months. Bulbs with inadequate food reserves will produce foliage but no flowers. Another possibility is the bulb was not exposed to proper temperatures (50 to 55 F for eight to 10 weeks) in fall. Temperatures of 50 to 55 F are necessary for flower development.
Amaryllis bulbs don’t require frequent repotting. It’s usually sufficient to repot amaryllis bulbs every three or four years. The best time to repot an amaryllis bulb is immediately after its rest period (cool period has been met). Remove the amaryllis from its pot, carefully shake or wash off most of the old potting soil, select a pot slightly larger than the bulb, and repot using fresh potting soil.