Hyacinths (Hyacinthus orientalis) obtained while they are blooming in a pot have exhausted the nutrients stored in their bulbs by the time they finish blooming. They are not likely to bloom ever again, If, though, particular potted hyacinths have sentimental value or you just like them a lot, then trying to save them may be worth the effort. Give the hyacinths a little extra care right from the start, and they might bloom again in two to three years.
Replacing Depleted Nutrients
Water the hyacinths when the top of their potting soil begins to get dry. Give them water-soluble houseplant fertilizer with a 10-10-10 ratio every two weeks, diluting the fertilizer with water first. A common dilution rate is ½ teaspoon of fertilizer per 1 quart of water, but the dilution rate depends on the fertilizer; follow your fertilizer's dilution instructions for potted plants. Fertilize the hyacinths immediately after watering their soil, or else their roots could be damaged.
Place the potted hyacinths in front of an east-facing window where they will get several hours of direct sunlight every day. If such a position is not available, then put them in front of a south- or west-facing window with a sheer curtain between the hyacinths and the window.
As the flowers fade, cut off the flower stems at their bases, using disinfected scissors. Disinfect the scissors with household disinfectant by wiping the blades with household disinfectant before using them to help prevent plant diseases. Rinse the disinfectant off the scissors prior to cutting a stem, and dry them with a clean towel. Cutting the stems will encourage the hyacinths to store nutrients in their bulbs rather than use nutrients to try to produce seeds. Do not damage the leaves. They produce food that will be stored in the bulbs and used next year.
Continue to water and fertilize the hyacinths until their leaves die back naturally.
Moving the Bulbs to a Garden
The hyacinth bulbs must be planted outdoors when they are done blooming. They will not grow and bloom again if kept in their container indoors.
Hyacinths are hardy in U.S. Department of Agriculture plant hardiness zones 3 through 9. In USDA zones 8 through 9, however, they may grow as annuals. Winter temperatures do not stay cold long enough in those warmer climates to satisfy the hyacinths' need for a cold rest period. The bulbs can be planted outdoors in the fall in those areas, but it is highly unlikely that they will grow or bloom.
If you live in a cooler climate, USDA zones 3 through 7, plant the hyacinth bulbs outdoors in spring or fall. Wait until their leaves die naturally before planting the bulbs outdoors in spring, or, if the leaves are still green in spring, plant the bulbs after your area's last average annual hard frost date.
Storing Them for Fall Planting
Store the hyacinth bulbs in a cool, dark area during summer if you prefer to plant them in fall. Stop watering and fertilizing the hyacinths when their leaves turn yellow and wither. Take the bulbs out of the pot after the leaves dry up, and brush the soil off the bulbs. Do not get the bulbs wet. Slip them into a mesh onion bag or a paper bag with holes in it, and store them at temperatures of 35 to 55 degrees Fahrenheit.
The bulbs can be stored in a refrigerator, but they should be sealed in a plastic bag first to keep the ethylene gas given off by fruits and vegetables from harming them. Hyacinth bulbs are toxic. Their ingestion may be fatal. So keep them out of the reach of children and pets.
Plant the hyacinth bulbs outdoors in a garden where they will be exposed to at least six hours of direct sunlight each day if you live in USDA zones 3 through 6. If you are in USDA zones 7 through 9, plant the bulbs in partial shade where they will get only four to five hours of direct sunlight daily. The soil must be fast-draining or else the bulbs will rot.
Make the bulbs' planting holes 6 inches deep. Plant each bulb separately in its own hole. Multiple hyacinth bulbs should be planted at least 5 to 6 inches apart from each other and other plants. Put 1 tablespoon of bonemeal in the bottom of each planting hole, and cover it with ½ to 1 inch of soil. Set the hyacinth bulbs into the holes with the top of the bulbs, from which the leaves grew, facing upward. Fill the remainder of each hole with garden soil. Water the hyacinth bulbs' soil right after planting. When planted in spring, the bulbs should not be given supplemental water; let rain water them. When planted in fall, the bulbs should be watered when the top 1 inch of their soil becomes dry, and that guideline should be followed until the end of fall.