8 Tips for Planting Flower Bulbs in Winter—Including How to Grow Them Indoors

While you may associate flowering bulbs with spring, the work for getting these beauties to bloom actually begins during fall and winter. Many bulbs can still be planted in the garden in late November and early December, depending on your zone. But if it's too late to plant outside, you can grow bulbs indoors and plant them in your garden after they bloom. No matter how you choose to plant flowering bulbs this winter, there are a few things to keep in mind as you care for them.

Plant Bulbs Before the Ground Freezes

You can plant bulbs outdoors in winter so long as the ground hasn't frozen. "Ideally, you’d like to get them in several weeks before the ground freezes because they will be actively putting down roots," says Peggy Anne Montgomery, horticulturist with FlowerBulbs.com.

Although it is possible to plant bulbs in winter if the ground isn't frozen, spring flowering bulbs are best planted in autumn when the weather is mild. "This is to allow the bulbs time to settle in and get some roots down before the winter cold sets in," says  Jake Davies-Robertson, arboretum supervisor at Kew Gardens.

Know Your Zone

This is when to plant bulbs outside by zone, says Montgomery.

• Zone 1 (below -50° F): Early September
• Zone 2 (-50 to -40° F): Early September
• Zone 3 (-40 to -30° F): Mid-September
• Zone 4 (-30 to -20° F): Late September to early October
• Zone 5 (-20 to -10° F): Late September to early October
• Zone 6 (-10 to 0° F): Mid-October
• Zone 7 (0 to 10° F): Early November
• Zone 8 (10 to 20° F): Early November
• Zone 9 (20 to 30° F): Early December
• Zone 10 (30 to 40° F): Mid-December
• Zone 11 (Above 40° F): Late December

Force Bulbs Indoors During Winter

If the ground has frozen and you've missed your opportunity to plant spring bulbs outside, grow them indoors instead. Many cold-hardy spring bulbs (tulips, daffodils, crocus, hyacinth, etc.) can be planted in pots to bloom indoors in late winter. Bulbs need time in the cold before they bloom; you can buy pre-chilled bulbs that have been given a cold treatment, forcing them into thinking it's winter—but it's also easy to do it yourself.

Know Which Bulbs to Grow Indoors

Many bulbs can be forced indoors, but some do better than others. "In general, smaller bulbs work best because they don’t get too tall and flop over," says Montgomery. "Personally, I like miniature daffodils and shorter tulip varieties. Some tulips can grow up to 2 feet, and they are liable to tip over and uproot themselves." Some other plants to consider include hyacinths, crocus, muscari, scilla, dwarf iris, anemones, and other small varieties.

Plant Bulbs Close Together

When growing bulbs indoors, be sure to plant them very close together, says Montgomery. Generally, about six tulip bulbs, three hyacinths, or six daffodils will fit into a 6-inch pot. Use a clean clay or plastic pot with drainage holes. Follow these steps when starting bulbs indoors:

1. Fill the pot about 1/3 of the way full with well-draining potting mix.
2. Place the bulbs in the soil with the pointed sides up, making sure to plant each bulb close together.
3. Cover small bulbs with a 1/2-inch of soil and larger bulbs up to their tips.
4. Water the bulbs well.
   

Give Bulbs a Cold Period

Spring flowering bulbs need a cold period and some moisture to put down roots. "The easiest way to do this is to put the pots outside and let Mother Nature do her thing," says Montgomery. "You can insulate them with a pile of leaves or mulch." Protect outdoor bulbs from rodents by covering the pots with chicken wire.

You can also chill bulbs indoors by keeping them in a cold garage, basement, or refrigerator. But if you choose the refrigerator, there's one caveat: "You can chill just the bulbs in the refrigerator but not near fruit because the ethylene they give off will hamper the process," says Montgomery.

Check on Bulbs During the Cold Period

Check soil moisture every few weeks while your bulbs are chilling. "Toward the end of the cold period, check to see if the bulbs have put down roots," says Montgomery. "That is a better indicator that they will bloom than the sprouts."

Bring Bulbs Inside After the Cold Period

When the bulbs have been chilled for the required length of time, bring them into the house and place them in a cool, sunny spot, says Montgomery. They'll flower about two to four weeks after coming out of the cold. "They will bloom for a shorter period indoors than they would outside," says Montgomery. "After they finish blooming, you can try planting the smaller bulbs outside."