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Horticulture and Home Pest News
Horticulture & Home Pest News is filled with articles on current horticulture, plant care, pest management, and common household pests written by Iowa State University Extension specialists in the Departments of Entomology, Horticulture and Plant Pathology.

Growing Amaryllis

This article was published originally on 12/7/2005

Growing Amaryllis

Amaryllis are popular flowering bulbs which are forced indoors for their large, spectacular blooms during the winter months. The trumpet-shaped flowers can be as large as 8 to 10 inches across and are produced atop an 18- to 30-inch-tall flower stalk. Flower colors include red, pink, orange, salmon, white, and bicolors. Single-flowering, double-flowering, and miniature amaryllis varieties are available.

Forcing Amaryllis

Amaryllis bulbs can be purchased pre-planted in pots or unpotted. When purchasing amaryllis, select large, solid bulbs. The largest bulbs usually produce 2 or 3 flower stalks.

When planting an amaryllis bulb, select a pot which is approximately 1 to 2 inches wider than the diameter of the bulb. The container may be clay, ceramic or plastic, but should have drainage holes in the bottom. Plant the bulb in a well-drained potting soil. Add a small amount of potting soil in the bottom of the pot. Center the bulb in the middle of the pot. Then add additional potting soil, firming it around the roots and bulb. When finished potting, the upper one-half of the bulb should remain above the soil surface. Also, leave about one inch between the soil surface and the pot's rim. Water well and place in a warm (70 to 75ºF) location.

Check the pot before watering a pre-planted amaryllis bulb. If the container doesn't have drainage holes, remove the bulb. Drill small holes in the bottom of the container and replant or transfer the bulb to a pot with drainage holes.

After the initial watering, allow the soil to dry somewhat before watering again. Keep the soil moist, but not wet. When growth appears, move the plant to a sunny window and apply a water-soluble fertilizer every 2 to 4 weeks.

During flower stalk elongation, turn the pot each day to keep the flower stalk growing straight. Flower stalks that lean badly may need staking.

Flowering usually occurs about 6 to 8 weeks after potting. When the amaryllis begins to bloom, move the plant to a slightly cooler (65 to 70ºF) location that doesn't receive direct sun to prolong the life of the flowers.

Care After Flowering

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 2 to 4 weeks with a houseplant fertilizer.

The amaryllis can be moved outdoors in late May. Harden or acclimate the plant to the outdoors by placing it in a shady, protected area for 2 to 3 days then gradually expose it to longer periods of sunlight. Once hardened, select a sight 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.

Reflowering of Amaryllis

In order to bloom, amaryllis bulbs must be exposed to temperatures of 50 to 55ºF for a minimum of 8 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 55ºF. 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 55ºF location for at least 8 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-lighted, 70 to 75ºF location. Keep the potting soil moist, but not wet, until growth appears. The other option is to place the plant in a well-lighted, 50 to 55ºF location in fall. Continue to water the amaryllis. Keep the potting soil slightly moist. The amaryllis foliage will remain green throughout the period. After the cool requirement has been met, move the plant to a warmer (70 to 75ºF) location.

Failure to Bloom

Amaryllis that fail to bloom may have contained insufficient food reserves in their bulbs. Failure to expose the bulbs to temperatures of 50 to 55ºF for 8 to 10 weeks could also be to blame.

Page References: 
114-115
Year of Publication: 
2005
Issue: 
IC-493(24) -- December 7, 2005