The giant amaryllis flowers commonly grown as winter-blooming houseplants are generally carefully bred hybrids derived from various species in the Hippeastrum genus, a group of tropical plants from Central and South America. These plants have strappy leaves and huge flowers shaped like trumpet lilies. The blooms are typically are a deep red, pink, white, or blend of these colors. You can expect your amaryllis to bloom for seven weeks or longer.
Controlling Bloom Time
If grown in a frost-free garden (zones 8 to 10), amaryllis will naturally bloom in March, April, and May, with fall rebloom possible. But amaryllis bulbs are often purchased to grow as potted plants for holiday bloom, which is only possible if you plant the dormant bulbs at precisely the right time—about 10 to 12 weeks before desired bloom time. When you buy commercial bulbs from a grower for Christmas bloom, these are dormant bulbs that should be kept cool until the right planting time.
If you already have potted amaryllis plants, future blooms can be controlled by setting the plant outdoors to grow through the summer, then bringing it indoors and forcing them into a short period of dormancy by withholding water and fertilizer for several weeks, then restarting the bulbs.
The techniques for growing amaryllis vary, depending on whether you’re growing it indoors or outdoors, and when you want it to bloom.
As a New Indoor Plant for Seasonal Blooms
Partially fill a 5- to 7-inch pot with a good-quality, well-draining potting mix, then plant the amaryllis bulb so the top one-third is exposed when you fill in the rest of the pot with potting mix. The bulbs should be planted 10 to 12 weeks before you want them to bloom.
Place a bamboo stalk alongside the bulb. The flowers can get top-heavy, and inserting the stake now will help you avoid damaging the bulb and roots later.
Water well, then place the pot in bright, indirect light and keep the soil moist, but not wet. A thick flower stalk should shoot up within a few weeks. The flat leaves will follow as the flower stalk matures. Turn the pot every few days, so the flower stalk gets uniform exposure on all sides and grows straight.
Forcing an Existing Plant Into Holiday Bloom
To force a potted amaryllis to bloom for the winter holidays, cut back the flower stalk after blooming stops, but allow the foliage to continue growing. You can place your plant outdoors for summer, if you like, in partial shade. Keep the watered so the soil is moist, but not wet.
Stop feeding in August. When it’s time to bring plants indoors, in September or October, move your amaryllis to a cool (55 to 60 degrees Fahrenheit), dry spot, and stop watering it. The foliage will already be dying back. If you want your amaryllis to bloom at a specific time, such as Thanksgiving or Christmas, count backward about 10 to 12 weeks, to determine when to stop watering.
The lack of foliage and water will induce the amaryllis to send out another flower stalk. Resume watering at this time and move the plant to a warm, sunny spot. Leaves will appear shortly followed by blooms. When the flowers fade, start the process over.
Allowing Potted Plants to Re-bloom Naturally
To allow your potted amaryllis to re-bloom naturally, cut off the flower stalk after blooming ceases, but let the foliage continue to grow as long as it can. Keep it in bright light, indoors or out. Keep the plant watered so the soil is moist, but not wet.
Stop feeding the plant in August. Bring it indoors before a frost hits it and place the pot in a cool spot in indirect, bright light. The leaves will start to yellow and drop around December. Keep watering as usual and new flower stalks should appear in a month or two. Resume feeding at this time and move the plant to a warm, sunny spot. Leaves will appear shortly, followed by blooms.
When the flowers fade, start the process over. Allowing the plant to bloom naturally in this way will result in larger plants and flowers.
As a Garden Plant
In zones 8 to 10, amaryllis bulbs can be planted in the garden. If your area is entirely frost-free, plant the bulbs with their necks at, or slightly above, ground level. In areas where frost is possible, set the bulbs with 5 to 6 inches of soil above them, followed by 5 to 6 inches of mulch. Water thoroughly after planting, but then water only when the top 2 inches of soil is dry.
After leaves appear, feed with a balanced fertilizer once each month until April. Garden amaryllis generally bloom in March, April, and May. When flowering is complete, remove the flower stalks, but leave the foliage to continue growing. If any leaves turn yellow, cut them off.
From June to September, water the plants only during dry periods. In fall, apply a layer of winter mulch if your area will see winter frost. The plants typically go dormant over winter.
Amaryllis will grow in full sun to part shade conditions. Outdoors, bright shade is the best environment. Grown as potted plants indoors, they prefer morning sun but bright shade in the afternoon.
Outdoors, grow amaryllis bulbs in well-drained, fertile soil. When growing potted bulbs, use a good-quality, well-draining sandy loam potting mix.
During the growing/ flowering period, water your amaryllis whenever the top 2 inches of soil become dry. Amaryllis requires a dry rest period immediately after flowering in order to reset the bulbs for future blooms. Forcing amaryllis into seasonal bloom requires careful manipulation of the watering schedule.
Temperature & Humidity
Amaryllis are tropical plants that prefer warm temperatures. Outdoors, they are hardy to zone 8, and zone 7 gardeners can sometimes overwinter them in the garden if the ground is heavily mulched.
During the growth period, feed your amaryllis with a half-strength water-soluble fertilizer every two to three weeks. After flowering, withhold feeding to induce the dormancy needed to reset the bulbs.
There are dozens of different amaryllis varieties, and the choice really depends on what flower color most appeals to you. Some recommended choices include:
- ‘Samba’: This variety has large red ruffled blooms with white markings.
- ‘Apple Blossom’: This popular variety has blooms that mix pink and white, with green throats.
- ‘Faro’: This plant has delicate flowers in pale salmon and white. The blooms are smaller and more delicate than with most varieties.
- ‘Summertime’: This plant has large 7-inch blooms in a unique watermelon pink to dark rose hue, with greenish centers.
- ‘Matterhorn’: This is a good choice for a pure white amaryllis. The throats are yellow-green.
When the flowers fade, cut the flower stalk back to just above the bulb. Keep watering the plant until it goes dormant in the fall. You can move the amaryllis outdoors for the summer, placing it in a part-shade location.
Common Pests & Diseases
Keep on the lookout for spider mites and mealybugs, which can be treated with horticultural oil. Outdoor plants may be feasted upon by slugs and snails.
If your amaryllis doesn’t bloom, it is often because it received no rest period after the last bloom, or because it is not receiving adequate light.
Information courtesy of TheSpruce.com