Forcing Bulbs Is Easier Than You Think—How to Do It Like a Master Gardener

If you haven't yet tried forcing bulbs, it's rewarding and easy enough for children. Look for packaged kits at retail stores in early autumn or purchase bulbs at your favorite nursery or online supplier.

Most spring-blooming bulbs can be successfully forced when done correctly. Here are some holiday favorites along with other popular bulbs including tips and techniques to add color and fragrance to your home during the winter season.

What Kind of Bulbs Can You Force?

Look for large, firm bulbs and pass on any that are discolored, moldy, or damaged. Here's a list you might like to try forcing:

• Amaryllis (Hippeastrum spp.): Amaryllis produces large (6- to 10-inch), trumpet-shaped flowers in white, red, pink, salmon, apricot, rose, or bicolor. Several blooms top each flowering stalk with some fragrant varieties. Toxic to humans and pets.
• Grape Hyacinth (Muscari spp.): Small bulbs each put out up to three short (4- to 8-inch) stalks with 20 to 40 tightly packed, purplish blue, bell-shaped florets resembling upside down bunches of grapes. Mildly fragrant.
• Hyacinth (Hyacinthus spp.): Each bulb produces a sturdy flower spike 6- to 10-inches tall. Highly fragrant blooms feature multiple, recurved florets in shades of blue, purple, pink, red and white. Toxic to pets.
• Crocus ( Crocus spp.): The age and size of bulbs determine how many flowers each will produce. Stems are usually under 6 inches tall with cup-shaped blooms in purple, yellow, lavender, cream, and white. 
• Daffodils (Narcissus spp.): Variety determines shape, size, color, and number of fragrant flowers produced by each bulb. Blooms feature trumpet-shaped centers surrounded by six petals and come in colors and combinations of white, pink, and orange, with or without yellow, from pastel to golden. Toxic to people and pets.
• Tulips (Tulipa spp.): Tulips usually produce one flowering stem per bulb, but there are exceptions. They range in height from 4 inches to more than 2 feet with shades that cover the color wheel except for true blue. Flower forms are most often cupped and may be single, double, or fringed. Generally unscented, a few varieties are fragrant. Tulips are toxic to pets.

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How to Chill Your Bulbs

Spring flowering bulbs are planted outdoors in autumn, giving them a natural chilling period over winter. To force bulbs, they need the same cold exposure to bloom. Exceptions are amaryllis and paperwhites which don't require chilling. Amaryllis blooms in six to 12 weeks depending on variety. Paperwhites bloom in four to eight weeks.

For flowers during December, start chilling spring bulbs in mid-to-late September. Average time to bloom after chilling ranges from three to five weeks. Depending on the bulb type you choose, add this to the required chilling time to estimate when they will flower.

Follow these chilling guidelines for spring bulbs:

• Crocus: 15–17 weeks
• Daffodil: 15–17 weeks
• Iris: 16–17 weeks
• Grape hyacinth: 15–17 weeks
• Hyacinth: 12–15 weeks
• Snowdrops: 10–12 weeks
• Tulip: 15–17 weeks

How to Force Bulbs in Water

Special vases called forcing vases are available for growing bulbs in water. They are narrow at the top allowing the bulb to remain suspended above water level. Otherwise, choose a clear glass container filled with pebbles or gravel. Of greatest importance is preventing water from touching the base of the bulb.

1. Place bulbs in the refrigerator in a paper or mesh bag for the required chilling period.
2. Check occasionally and discard any that are dried out, mushy, or moldy.
3. When small white roots start to form, remove bulbs from the refrigerator and place them in forcing vases or on top of pebbles or gravel in a clear glass container.
4. Add water to cover only the roots keeping water level below the bottom of the bulb.
5. Place containers in a location with indirect light.
6. Check the water frequently to make sure roots remain in the water.
7. Once flower buds form, move containers to a location with more light.
8. Replace water every few days or whenever it gets cloudy.
   

How to Force Bulbs in Soil

1. Choose a plastic or clay pot with good drainage twice as deep as bulb size.
2. Fill the pot with quality potting mix leaving room for bulbs at the top.
3. Place bulbs on the soil surface then fill in around them leaving just the tops exposed. Follow any specific instructions for orienting your bulb such as placing a pointed end up or down.
4. For the most attractive display, place several bulbs in one container spaced about half a bulb width apart.
5. Water pots well allowing all excess to drain.
6. Place in a cool, dark location with temperatures between 40°F and 45°F. Unheated garages, basements, or refrigerators work well.
7. Check soil occasionally, adding water if dry. Overwatering causes bulbs to rot.
8. Or place bulbs in a paper or mesh bag and store them in the refrigerator for the required chilling period. Do not store bulbs near fruit which emit gases that cause them to fail.
9. When bulbs start to develop shoots, move them to a location with medium light. Now is the time to pot them up if they aren't already in containers. The shoots may appear white due to lack of light but will green up.
10. When flowering occurs move plants of out direct sunlight to extend the bloom period.