How To Force Bulbs For Indoor Blooms

by Suzanne DeJohn

Imagine your house filled with pots of blooming tulips, daffodils, and hyacinths, brightening your home while winter lingers outside. You can enjoy indoor flowers like these by "forcing" bulbs into early bloom.

About Forcing

Forcing bulbs is a technique used to coax hardy bulbs into blooming indoors. Unlike tropical bulbs like amaryllis, spring-blooming bulbs like daffodils and tulips need to go through an extended cold period of about 3 months. During this time, the plants grow roots and the flower buds begin to form inside the bulbs. This cold period mimics the cold temperatures they'd experience if they were planted outdoors.

So if you want the bulbs to bloom indoors, you have to fool them into thinking they've spent a winter in the garden.

Tulips, daffodils, hyacinths, crocus, grape hyacinths, and dwarf iris are all good candidates for forcing.

Potting Up the Bulbs

You can use any type of container for forcing. Add some moist commercial potting mix and set in the bulbs pointy side up, crowding them together so they're almost touching. Add as much soil as necessary so that the tops of the bulbs are just visible, then water lightly to settle the soil.

Chilling

Next comes the cold treatment. You'll need to find a dark place that stays between 35 and 50 degrees F for the next three months or so. Depending on your climate, it could be an unheated attic, cellar or garage, or a cold frame outdoors. It's important that the bulbs don't freeze. A refrigerator is an ideal place to chill bulbs, if you have the space. Just be sure to the potted bulbs away from stored fruit, as ripening fruit emits ethylene gas that can harm the bulbs. Check the soil moisture every few weeks; stick your finger in the soil and if it's dry down a few inches, water the soil lightly. Don't soak the soil or the bulbs may rot.

Bringing Into the Warmth and Light

Begin checking the pots after about two months. As soon as you see emerging shoots, they're ready to bring into the warmth. (Bring them in after three months even if you don't see shoots.) Place the pots in a bright, cool room (55 to 60 degrees F) and keep the soil slightly moist. There's no need to fertilize; the bulbs contain all the "food" the plants need to grow and flower.