FORCING BULBS INTO an early bloom is easy. That said, no one really gets to compel Mother Nature. “Forcing” is simply a matter of tricking the plant into and then coaxing it out of an artificially imposed winter. This is accomplished by providing a cold, dark rooting period before bringing the bulb into progressively warmer and brighter conditions.
While most spring-blooming bulbs can be forced, hyacinths are ideal, and their powerful fragrance on our windowsill is just the boost we need to get us over the finish line of winter.
Unlike most tulips, hyacinths reliably bloom year after year in the garden. However, their blossoms have an almost rigid formality in their first year, like earnest floral soldiers lined up along a pathway. This vigor and strength, which can be a bit too much of a good thing in the garden, allows hyacinth bulbs to withstand the rigors of forcing without depleting the plant altogether.
Select firm, healthy bulbs for forcing, avoiding any that are showing top growth, as the flower won’t fully emerge without first forming a good root system. Hyacinth bulbs can also be forced in water using special hourglass-shaped vases, but I prefer potting bulbs in soil because they’re easier to stash during the rooting period without spillage.
Choose containers (with drainage holes) that are twice as deep as the bulbs you are planting to allow ample room for root development. Bury each bulb so its nose is at soil level to anchor the plant and prevent it from tipping over under the weight of its top growth. You can plant a single hyacinth in a 4-inch pot or multiple bulbs placed shoulder-to-shoulder in a larger container. (Note: The papery sheath around each hyacinth bulb contains oxalic acid, which can cause an itchy rash. Thoroughly wetting the bulbs before handling them reduces irritation, but I always wear gloves to avoid this harmless but annoying nuisance.)
Label each pot with the name of the bulb variety, the planting date and anticipated chilling period. Hyacinths require 10 to 12 weeks of chilling while rooting takes place. Water containers well, and place the potted bulbs in a cool, dark location where temperatures will remain between 40 to 48º F. A cool basement, garden shed or dark garage all work well if temperatures are constant. I stash my pots on a shelf beneath my outdoor potting bench covered with a box to keep out light. Soil should be kept moist but not soggy during this critical growth stage.
After the appropriate time has elapsed, check to see that roots have grown to fill the container by gently turning the pot over. Sneak a peek by tapping the pot to release the root ball. Actual forcing begins when you bring the containers into an environment that will trigger the growth of leaves and flowers, like a sunny windowsill at room temperature. Keep soil evenly moist.
When flowers begin to show color, moving the plants to indirect light and cooler temperatures will prolong blooming. After blooming, plant forced hyacinths out into the garden, and allow the foliage to mature and ripen completely (that is, die off naturally) to rebuild reserves for future blooms. Subsequent years find this sweetly scented harbinger of spring relaxing its stance as the single turgid bloom stalk relaxes into multiple stems of looser and far more delicate blossoms to enjoy for years to come.