Text by Katie Dubow for the September/October 2013 issue of Horticulture.
When you think of forcing bulbs, paperwhites and amaryllis are the first—and often only—kinds that come to mind. This season, consider adding something different by growing grape hyacinth (Muscari spp.) in pots.
Averaging about eight inches tall, grape hyacinths are easy to grow during mid-winter months in a container, in water or even in a paper bag. Their tight clusters of flowers look like tiny bunches of grapes, inspiring their common name. Although small, these flowers have a big impact in containers with their delicate fragrance and striking blue color. They are also varieties with white or two-tone flowers.
How to Force Grape Hyacinths
Grape hyacinths are the favorite bulbs to force of third-generation grower Hans Langeveld, owner of Dutch bulb company Longfield Gardens. For forcing muscari or other spring-flowering bulbs, he suggests starting with top quality, good-size bulbs and then deciding how you want to force and display them. He suggests planting them in masses in a container, as you would in the garden.
“There are many ways to force a bulb,” Langeveld says, “But the most important factor is chill time.” Muscari requires eight to ten weeks of cold treatment to bloom.
Fill a pot loosely with potting mix and set bulbs side by side (not touching), pointed end up. Cover loosely with soil, leaving the tips of the bulbs exposed.
Water thoroughly and move the container to a cool, dark location (40˚F), such as a basement, garage or refrigerator. If you are storing in a refrigerator, be sure to keep the bulbs away from fruits and vegetables, because as these ripen they can give off a gas that diminishes the bulbs' ability to bloom.
Keep an eye on the container. When shoots reach two inches tall, you can bring the container out of storage. Keep the soil moist, and gradually move the pot toward a sunny window. Turn the container several times a week to encourage even growth.
Grape hyacinths also respond well to the paper-bag method of forcing. Simply punch a few small holes in a paper bag, place the bulbs inside and loosely close it. Watch for shoots and then plant the bulbs into a container, or grow then on in a bulb vase or shallow dish with rocks.
Flower buds should appear on the plant's tiny stalks within two to three weeks of sprouting. Muscari tend to have shorter stems when forced, but you can overcome this problem by placing the plants in a warm but still dark location for a few days, or placing a paper cone over the plants in order to "draw" the flower out of the bulbs. Forced bulbs are not likely to flower again, so discard the bulbs once the flowers fade.