Bulbs for winter blooms — How to force flower bulbs indoors

Here’s a plant project that brightens the longest winters. It’s easy to do (seriously — I detest when directions, whether for a recipe or a DIY craft, say it’s easy when it’s not!), and it’s so rewarding. Basically, you plant some flower bulbs indoors, chill them, and watch them bloom. If you time it right, you can grow flower bulbs indoors all winter long!

This process is called forcing bulbs, which means you’re making the bulbs bloom when they normally wouldn’t. (The chilling substitutes for a winter outdoors, and the bulbs are tricked into thinking it’s spring!)

Many people like to plant amaryllis and narcissus for blooms during the holiday season, or to give as gifts. I especially like to plant bulbs indoors so that when the winter holiday festivities are over and we’re awaiting spring, I have beautiful flowers to tide me over. 

Choosing and storing bulbs for blooming

Some bulbs are better for forcing than others. You can purchase bulbs for forcing online or at a local gardening shop. When choosing, avoid bulbs that have soft areas or that have started growing roots. Choose large, firm bulbs without nicks or bruises. (Larger bulbs usually mean larger blooms.) 

pink and white amaryllis blooming inside a window

You need to store your bulbs correctly until you’re ready to plant them. Place the bulbs in a paper bag, then store them in the refrigerator — unless you have paper white narcissus or amaryllis, which should be stored in a dark, dry, cool place other than the refrigerator. 

Don’t store fruits or vegetables that release ethylene gas (such as apples and avocados) in your refrigerator at the same time as your bulbs, because the gas can damage the bulbs. (For a list, see our article on storage tips for fruits and veggies.) Dedicated bulb growers designate separate little refrigerators for their bulbs or steal space in a “beer fridge.” (See “Chilling the planted bulbs,” below, for more options.)

Here are some bulbs that are especially suitable for indoor forcing with the chill time plus transition time you’ll need before blooming:

Amaryllis (No chilling, 5-8 weeks to bloom)

Bulbous iris (15 weeks chilling, then 2-3 weeks to bloom)

Checkered lily (14 weeks chilling, then 3-4 weeks to bloom)

Crocus (10-12 weeks chilling, then 2-3 weeks to bloom)

Daffodil (narcissus) (12 weeks chilling, then 2-3 weeks bloom)

Dwarf iris (8 weeks, then 2-3 weeks to bloom)

Grape hyacinth (muscari) (10 weeks chilling, then 2-3 weeks to bloom)

Hyacinth (12 weeks, then 2-3 weeks to bloom)

Paperwhite narcissus (No chilling, then 3-4 weeks to bloom)

Siberian squill (15 weeks chilling, then 2-3 weeks to bloom)

Snowdrop (8-11 weeks chilling, then 2-3 weeks to bloom)

Tulip (12-14 weeks chilling, then 2-3 weeks to bloom)

Placing/potting your bulbs.

There are two ways to force bulbs indoors. One is to simply set them above some water, and the other is to pot them. Here are the two options:

a bulb growing indoors in an hourglass forcing vase

Grow in vases, sitting atop water.

I love the little hourglass-shaped vases made for forcing bulbs. These little vases/jars have a narrow neck so that the bulb can sit in the top part and the roots can grow in the water below. The hourglass shape keeps the bulb out of the water. 

The best bulbs for these vases are small varieties. Simply fill the bottom portion of the vase with water, then sit the bulb in the top portion, with the root end down. The bulb should sit about ¼ inch above the water — the roots will reach down into the water.

You can also plant bulbs above water in a regular glass vase. Place pebbles or gravel in the bottom of the vase (I usually use a straight-sided vase and fill it halfway with the pebbles). Sit the bulb on top of the gravel or pebbles, and water up to ¼ inch below the bottom of the bulb. If you choose a clear glass vase, you can watch the progress of the roots. 

Grow in a pot of soil or gravel.

Choose a pot with good drainage. The size should be about double the depth of your bulb. Hyacinth and crocus will need a smaller pot than amaryllis or tulips, for example. Bulbs — especially small bulbs — often look especially nice when planted in shallow, wide pots rather than tall ones.

Fill the pot with gravel or potting soil that’s on the sandy side. (Either purchase sandy soil or combine standard potting mix with equal parts sand or perlite.)  Then plant the bulbs, making sure the root end is down. Plant them so that only about half of the bulb is below the soil or gravel; the rest should be above soil or gravel level. If planting more than one bulb per pot, space them about half an inch apart. (They don’t need much room and look better cozied up, but they shouldn’t be touching!) Water until moist, but not wet — soggy soil will cause the bulbs to rot!

sprouting flower bulbs

Chilling the planted bulbs

Most bulbs need to be chilled after planting. Exceptions are paper white narcissus and amaryllis, bulbs that are native to warm climates. Nature doesn’t chill them, so you don’t need to, either. 

To provide their “winter,” simply place your potted bulbs in a refrigerator, cool cellar, unheated garage or shed, etc. The temperature should be about 35 to 45 degrees F. You don’t want to freeze the bulbs, but they need to be cold. Some growers like to chill their bulbs outdoors, in a box or crate with insulation (such as straw or blankets) around them to prevent freezing. I find it difficult to monitor the temperature beneath the insulation. (You also have to be wary of rodents getting into your bulbs and chewing on them when they’re left outdoors, so I prefer my refrigerator.) 

Water when the top inch of gravel or dirt is dry. If your bulbs are in the refrigerator, you may only need to water them about once a month. If they’re out in the garage, in the cellar, or outdoors, they may need more frequent watering, even weekly drinks. (if using the sitting-atop-water method), refill the water level in the vase when it drops below ¼ inch.

Note: If you’ve purchased bulbs specifically for forcing, the grower may have already pre-chilled them for you. The packaging should tell you if this is the case. You can count any pre-chilling time (specified on the packaging) plus any time you’ve chilled the bulbs before planting towards your total chilling time for the bulbs. 

potted grape hyacinth

Encouraging blooms

Your bulbs are ready to take out of chilling when they’ve sprouted some greenery on top and grown some roots below. You’ll be able to see the mass of roots in the jar, and if your bulbs are in soil or gravel, carefully take a peek to see if they have at least a couple of inches of growth and feel well rooted. 

After your bulbs have served their chilling times and established some roots, bring them to a warmer indoor location (50 to 65 degrees F is perfect), with little light. (You are gently transitioning them to their blooming location.)

After about a week in this transition area (when flower buds are beginning to show), move them to a spot where they’ll get more warmth (room temp) and bright but filtered light (not direct sunlight, which will cause the blooms to deteriorate more quickly). Do your best to keep your bulbs away from blasts of cold or hot air (doorways and heat vents, for example). Within a month, your plant will bloom! BTW, the “room temp” your bulbs will thrive best in is about 65 degrees or so. If you keep them in a very warm room, they’ll blossom, but the blooms won’t last as long as they would in a cooler environment. 

There’s no need to fertilize; the bulb contains all the nutrients it needs. But continue to water when the soil becomes dry or the water level in the vase drops. And trim off dying blossoms so all the bulb’s energy can go to new blossoms.

Can I plant the bulb outside when it’s finished blooming?

Give it a try! Most people declare the bulbs spent once they’ve been forced indoors, but some of us have had some success. It just takes a little patience. 

purple and white tulips blooming in a terra cotta pot

If you want to give it a try, leave the bulb in its pot or vase in its warm, sunny location. Give it some fertilizer when it’s finished blooming but the foliage is still green. Continue watering it until the foliage dies back. Then let the soil dry and remove the bulb. Put it in a paper bag with sawdust in the bottom and store in a cool, dry place, like a dry basement. 

Plant outside in the fall and cross your fingers. Be patient — it may take the bulb a couple of years to gather enough nutrients to bloom again. 

Once you bring beautiful blooms (and sometimes fragrance) into your home with forced bulbs, you might just make it an annual fall ritual. You’ll be glad you did, especially when the winter days seem so dreadfully far from spring blossoms!

You might also enjoy:

How to repot a plant

How to care for orchids

TLC for your Tilly — How to care for air plants (Tillandsias)

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