Almost any bulb can be brought to bloom indoors through the simple process of "forcing."
Convincing flowers to bloom indoors out of season may seem like it requires brute force, but really it's mostly a matter of timing. Understanding what bulbs need to bloom and providing those conditions is actually fairly simple. Amaryllis and paperwhites are holiday traditions, but almost any bulb can be brought to bloom indoors. Now is the time to start forcing paperwhites for Christmas and amaryllis can be bought just as they are about to bloom, right up to the holiday. But I enjoy indoor blossoms far more in the post-holiday gloom of January and February than when they have to compete with the glitter of holiday lights. To brighten midwinter days, consider starting a second round of these two flowers right before the holidays, or try a slower flower and introduce some variety into your winter centerpieces.
Amaryllis is a popular winter flower because it is as easy as it is beautiful. Their huge red flowers are almost synonymous with Christmas, but amaryllis cultivars have white, pink, and even candy-striped flowers that evoke spring more than Santa. While the common name amaryllis continues to be used, the flower is properly classified as belonging to the genus Hippeastrum, and is native to the tropics of South America. This means that unlike most spring-flowering bulbs, which need a period of cold to bloom, amaryllis' cycle of growth and dormancy is controlled by soil moisture. Amaryllis bloom after six to eight weeks of growth, and are usually sold when they are ready to bloom. Amaryllis do best when kept warm and in bright light until the flower buds begin to show color.
Many types of bulbs are spent after forcing, but amaryllis can be coaxed to bloom repeatedly by replicating their native moisture cycle. Cut the finished blooms and treat the amaryllis like a sun-loving houseplant until it is warm enough to plant outside. Keep the plant outdoors in full sun all summer. Before the first frost, bring it inside and store it in a dark place. Allow the pot to dry out completely for about two months. Then repot your bulb, begin watering it again, and bring it into sunlight for a new round of blossoms. The more sunlight and heat you give your amaryllis, the faster you will get flowers. If you want to delay blooming until later in the winter, wait a bit longer to start watering, and grow your amaryllis in a cooler room with fewer hours of bright light.
If you're looking for a subtler blossom than the bold amaryllis or if you’re craving fragrance, paperwhites are just as easy as amaryllis. Paperwhites are a subspecies of Narcissus tazetta, and unlike other Narcissus, they don’t require chilling before they bloom. In fact, paperwhites don’t even need soil. Forcing them is really as simple as setting the bulbs into a base of pebbles or glass marbles and adding water. Keep the water level just above the bottom of the bulbs. Paperwhites will appreciate all the light they can get, but if the room is too warm, they will grow tall and floppy. They will bloom in about three weeks.
Paperwhites can be brought to bloom again, but it takes two to three years. Once the flowers are done, pot the bulbs in soil and treat them like a regular houseplant. Cut the leaves after they are completely brown. Once all the leaves are gone, stop watering the pot to initiate dormancy. Repot the bulbs and begin watering again in the fall. Eventually you will get flowers again. If this is too much work, you can also plant the bulbs outside and forget about them. They might surprise you.
Other Spring Bulbs
Tulips, daffodils, crocuses, bluebells, grape hyacinth, lily of the valley, and snowdrops can all be forced indoors, following roughly the same procedure. Each flower has its own chilling requirement, with different optimum temperatures and durations. Chilling can often be achieved by storing the bulbs in a paper bag in an unheated garage in colder climates, but a refrigerator is required if you live somewhere warm or are trying for later blooms extending into summer. When shoots first emerge after cold storage in the dark, most bulbs benefit a week or two in dim light and cool temperatures before being placed on display in the house.
* Lily of the Valley – They seem so delicate, most people are surprised that lily of the valley are so easy to grow indoors. No chilling is needed; simply soak the pips in warm water until they swell. Then pot them like houseplants and you’ll have flowers in about three weeks.
* Grape Hyacinth – Grape hyacinth require at least ten weeks of cold storage. Once they sprout, they will grow quickly, with long-lasting blossoms often arriving in under three weeks. Once spent, bulbs can be planted outside, where they will eventually take over your entire yard.
* Daffodils – Most daffodils require 13 weeks of chilling. Longer cold storage will result in taller flowers. Once brought into the house, cooler temperatures and direct sunlight will produce the best results. Daffodils will flower in three to four weeks.
* Tulips – The size of tulip bulbs can affect how long they need to chill, as can the time when you start to force the bulb. Large bulbs started in October may take up to 16 weeks of chilling while a smaller bulb started in December may only need eight weeks. Once they sprout, warm daytime temperatures will speed growth while cool nights will help flowers last longer. Allow about three weeks for flowers to bloom once bulbs break dormancy.
* Crocuses – Crocus corms are best chilled in moist soil for about 12 weeks. The plants will grow best with bright, indirect light and cool temperatures that drop even lower at night. Crocuses cannot be brought to bloom indoors twice, but may bloom again eventually if planted outdoors.
* Snowdrops – These ephemeral flowers are for the truly dedicated. Up to 15 weeks of chilling is required before you can briefly enjoy their blossoms indoors. Plan on growing snowdrops near a drafty window, as the optimal temperature for growth is 60 degrees, only slightly warmer than the 45-50 degrees needed for chilling. Snowdrops will bloom about three weeks after they begin growing.
Hyacinth has a reputation for being as difficult to force as amaryllis is easy. But these fragrant, old-fashioned flowers are so worth the effort, which isn’t really as great as it's made out to be. Two factors contribute to hyacinth's diva-like reputation. First, they require a longer cold period than many other flowers. Eight weeks is the minimum, but some varieties may need as long as 16 weeks. The second factor is that hyacinths are not stored dry during their rooting period. Traditionally, hyacinths have been suspended over water in special vases (or you can try the toothpick method commonly used to sprout avocados) in a cool, dark place for the 8 to 16 weeks that it takes for the roots to fill the vase. Occasional water changes are required. When the vase is filled and the leaves are only a couple of inches tall, hyacinths can be brought into the house. Early spring bloomers, hyacinths do well in cool, dim spaces, so those who live in old houses in Northern climates can rejoice.
If weeks of checking water levels in the garage seems impossibly daunting, remember the traditional way is not always the best way. Refrigerators are generally considered too cold to root hyacinths successfully, but many people have had success forcing their hyacinths with the same techniques they use for other bulbs (see above). The varieties 'Lady Derby' and 'Gipsy Queen' are reputed to be particularly promising for this easy method.