Prepared by Nancy Doubrava, HGIC Horticulture Specialist, and Bob Polomski, Extension Consumer Horticulturist, Clemson University. (New 06/99.)
The large bell-shaped or lily-like flowers of the amaryllis (Hippeastrum species) and its hybrids make excellent garden and potted plants. They are available in a wide range of flower colors including red, white, pink, orange, salmon or bicolored and typically have two to six flowers per stalk. Most of the bulbs sold are either Dutch or South African grown hybrids that will flower without special treatment when first purchased.
The planting and care is the same for amaryllis bulbs, whether you are repotting an old bulb that you’ve saved or a new one just purchased. However, with the bulbs that you have saved, cut off the old dried leaves before replanting the bulb.
Soil Mix & Container: Amaryllis can be potted or repotted anytime after the plants have gone through a dormant or rest period which is in fall or winter. Late November is considered to be an ideal time.
Plant the bulb in a container that is one to two inches larger in diameter than the base of the bulb. Potted bulbs thrive under conditions in which they are slightly rootbound. Containers can be either clay or plastic, and they must have drainage holes in the bottom.
Plant amaryllis with about one-third to one-half of the bulb above the growing medium surface. This keeps the bulb’s nose dry, which helps reduce red blotch infection, a fungal disease.
Plant in a well-drained, sterilized potting medium with a soil pH between 6.0 and 6.5. A mixture containing equal parts peat and perlite is excellent.
Light & Temperature: The sun-loving amaryllis grows best indoors in a well-lighted area that receives at least four hours of direct sunlight each day. A southern window exposure is best, while an eastern-or western-facing window is second best.
Amaryllis prefers warm temperatures (70 to 75 °F) for best growth until the roots form and the leaves and flower stalk begins to grow. Once the plant flowers, cooler temperatures (65 °F) will prolong the life of the flower.
Water: Immediately after planting, thoroughly water the bulb. Keep the bulb in a slightly moist soil condition until flowering. When flowering starts, increase the frequency of watering. It is best to water your plant when the soil surface feels dry to the touch. Watering once per week is usually adequate.
Fertilizer: Fertilizing an amaryllis bulb that has no leaves can kill the roots, but after the plant begins to grow fertilization is essential. Fertilize amaryllis twice a month using a soluble fertilizer recommended for pot plants at full strength and frequency.
Care After Flowering: The secret of successfully growing amaryllis is to keep the plants actively growing after they finish blooming. Remove the blossoms as soon as they fade to prevent seed formation by cutting the stem off just above the bulb. Place in a sunny window. During the next several months growth is active and should be encouraged for future bulb development.
Keep the soil slightly moist and fertilize with a balanced houseplant fertilizer at regular intervals. You can continue to grow your amaryllis indoors all year, or outdoors as soon as the danger of frost has passed in the spring.
Reflowering of the Bulb: There are several things that you need to do to reflower your potted amaryllis. First, stop watering and fertilizing it for 8 to ten weeks. The leaves will yellow and wither. When you see the top of the flower bud beginning to emerge, put the pot in a sunny area and start watering it again. Remove all dry foliage. As the flower stalk begins to lengthen, rotate the plant every few days to prevent the stem from leaning towards the light.
Amaryllis makes a great landscape plant, and is hardy in South Carolina through Zone 7b. Plant new bulbs outdoors in late September or early October for spring flowers. Amaryllis grown indoors from the previous holiday season can be moved outdoors in the spring. Gradually acclimate the indoor plants to brighter light by first moving them to a porch or patio area before planting them in the garden.
Amaryllis grow well in almost any good garden soil as long as the site is well-drained. An elevated planting bed may be necessary to ensure good drainage. A soil rich in organic matter will provide the best growth. Plunge the entire container into the ground up to the rim, or plant bulbs directly into the ground. Space bulbs about a foot apart. Plant the bulb with only half of its nose above ground, leaving the tops barely covered with soil.
Select a sunny spot in the garden that receives some shade during the afternoon hours. Avoid placing the bulb where it will dry out excessively. Apply mulch, especially during the fall and winter months.
Fertilization determines the size and quality of the flowers and foliage. For garden plantings, use fertilizers containing low nitrogen, such as 5-10-10 or 6-12-12 analysis. Apply 1 to1½ pounds per 100 square feet or 100 feet of row to be established. A bulb booster type fertilizer can also be used. Make the first fertilizer application as new growth begins, then repeat the application when the flower stalk is 6 to 8 inches tall. Apply a third application immediately after flowering when the old flower heads and flower stems have been removed.
The main disease problems of amaryllis are mosaic virus, bulb rots and "red blotch." Plants infected with mosaic virus have a light yellow streaking of the leaves and reduced growth and flowering over the years. There is nothing one can do to eliminate mosaic from an infected plant.
Bulb and root rot problems typically occur when the soil is kept too wet or by planting bruised bulbs. When bulb or root rot problems are suspected, discard diseased bulbs and replace soil.
The fungal disease "red blotch" causes reddish brown spots on the bulb, leaves and/or scape. It can spread rapidly within a bulb and from bulb to bulb.
Insects and other pests that can become a problem include scale, mites, thrips, bulb maggots and mealybugs.
Excerpted from Understanding and Producing Amaryllis, HL 63.
Home Forcing of Potted Amaryllis, North Carolina State University, Leaflet 8529, 1994.
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