By Richard Jauron
Hyacinths are a popular spring plant, but planning ahead during colder weather can make them easier to enjoy before warm temperatures arrive next spring. What are important steps to forcing their bulbs indoors, and how can it be done successfully?
ISU Extension and Outreach horticulturists can help answer questions about how to enjoy hyacinths during winter. To have additional questions answered, contact the ISU Hortline at 515-294-3108 or hortline@iastate.edu.
What is needed to successfully force hyacinths indoors?
Good quality bulbs, a well-drained potting mix and containers with drainage holes in the bottom are needed to successfully force hyacinths indoors. To enjoy hyacinths in winter, gardeners must begin the forcing process in late summer or early fall.
Which hyacinth cultivars can be forced indoors?
Hyacinth cultivars suitable for forcing indoors include ‘Amethyst’ (lilac purple), ‘Blue Jacket’ (navy blue), ‘City of Haarlem’ (soft primrose yellow), ‘Delft Blue’ (porcelain blue), ‘Gipsy Queen’ (salmon apricot), ‘Jan Bos’ (pinkish red), ‘Peter Stuyvesant’ (blue purple), ‘Pink Pearl’ (deep pink), ‘White Pearl’ (white), and ‘Yellow Queen’ (yellow).
How do you force hyacinth bulbs indoors?
Begin by partially filling the container with potting soil. Then place one or more hyacinth bulbs on the soil surface. Adjust the soil level until the tops of the bulbs are slightly below the rim of the container. The number of bulbs to plant per pot depends on the size of the container. A single hyacinth bulb is appropriate for a four-inch-diameter pot, while three bulbs make an attractive floral display in a six-inch-diameter pot.
Once the bulbs are in position, place additional potting soil around the bulbs. However, do not completely cover the bulbs. Allow the bulb tops (noses) to stick above the potting soil. For ease of watering, the level of the potting mix should be ½ to 1 inch below the rim of the container. Label each container as it is planted. Include the name of the cultivar and the planting date. After potting, water each container thoroughly.
In order to bloom, hyacinths and other spring-flowering bulbs must be exposed to temperatures of 40 to 45 degrees Fahrenheit for 12 to 16 weeks. Possible storage sites include a refrigerator, root cellar or trench in the garden. (When using the refrigerator for storage, place the potted bulbs in a plastic bag if the refrigerator contains apples or other ripening fruit. Ripening fruit give off ethylene gas which can inhibit flower development and plant growth.) During cold storage, keep the potted bulbs in complete darkness and water the bulbs when the potting soil begins to dry out.
Begin to remove the potted hyacinth bulbs from cold storage once the cold requirement has been met. At this time, yellow shoots should have begun to emerge from the bulbs. Place the hyacinths in a cool (50 to 60 degree Fahrenheit) location that receives low to medium light. Leave them in this area until the shoots turn green, usually in four or five days. Then move them to a brightly lit, 60 to 70 degree Fahrenheit location. Keep the plants well-watered. Turn the containers regularly to promote straight, upright growth. On average, flowering should occur three to four weeks after the bulbs have been removed from cold storage. For a succession of bloom indoors, remove pots from cold storage every two weeks.