The Gentle Art of Forcing Bulbs: Spring Blooms in Winter

In the dead of winter, spring-blooming bulbs are especially welcome in the house. They easily fill a room with delightful perfume and remind you spring is just around the corner.

The process of getting flower bulbs to bloom ahead of schedule is called forcing. Depending on the bulbs, you could enjoy first blooms in less than 10 weeks.

We list several popular bulbs, available at most nurseries and garden centers this month or via mail-order catalogs. Many bulbs require chilling; some need refrigeration, others can be planted then chilled outdoors (see Forcing Tips). Chilling periods below are based on Netherlands Flower Bulb Information Center recommendations.

Crocus and Hyacinths

Must be chilled. Can be forced, one bulb per jar or vase, in water alone without soil; special forcing jars and vases exist.

• Crocus corms need 15 weeks refrigeration. After chilling, place each in water-filled crocus forcing jar/vase at ~60°F; flowers emerge in ~2 weeks. Choose Crocus vernus in purple, lavender, yellow, white.
• Hyacinth bulbs need 12 weeks refrigeration. Then place each in water-filled hyacinth forcing jar/vase at ~70°F; flowers follow in 2–3 weeks. Try fragrant Dutch hyacinths in blue, purple, pink, white.

Freesias and Tazetta Narcissus (Paper Whites)

Technically don't need chilling but need cool night temperatures and plenty of time to root before flowering. Powerfully fragrant.

• Freesia corms take ~14 weeks from planting to bloom. Plant in container with potting soil or sand, in spot with daytime sun and nighttime temps in 40s. Look for Dutch and Tecolote hybrids in purple, blue, lavender, red, pink, orange, yellow, white.
• Tazetta narcissus bulbs take 5–7 weeks from planting to bloom. Use any container twice as wide as high. Bulbs can be completely buried in potting soil or partially sunk in horticultural sand, decorative rocks, or pebbles. Water well, put in cool place (40–50°F night perfect) until buds show color, then bring indoors to bloom. Many fall under "paper white"; all produce lots of flowers per bud. Best for forcing: Narcissus tazetta 'Orientalis' (light yellow segments, deep yellow cup), 'Paper White' (all white), 'Grand Soleil d'Or' (golden yellow), Israeli series 'Galilee' (white), 'Nazareth'/'Yael' (pale yellow segments, deep yellow cups), 'Ziva' (white).

Other Daffodils and Tulips

Require more effort. Need plenty of time to develop roots to support tall, heavy tops. Plant in potting soil, then chill at 45°F or below for extended period. Then bring indoors to bloom at room temperature. Use container with drain hole.

• Daffodil bulbs need 16 weeks chilling; bloom follows 2–3 weeks later. Try 'Salome' (pale yellow segments, apricot pink cup), diminutive 'Tête à Tête' (all yellow), 'Mount Hood' (all white).
• Tulip bulbs need 14–20 weeks chilling; bloom ~3 weeks later. Choices range from low species tulips to tall hybrids. Favorites for forcing: red T. greigii (try 'Orange Toronto') and T. kaufmanniana with water lily-shaped flowers in yellow or red ('Showwinner' superior red). Each holds flowers ~1 ft high.

Forcing Tips

• Chilling. To chill in refrigerator, store in mesh/paper bag in crisper until ready. Throughout much of the West (except mild-winter Arizona and Southern California), chill after planting by putting pots outdoors. In very cold regions, use garage, greenhouse, coldframe; in milder places, cool bright part of garden. Bulbs root and sprout during chilling.
• Containers. Shop for containers and special forcing jars/vases at garden centers and mail-order. Tall glass vessels like hurricane-lamp chimneys support spindly/extratall stems; wire supports also keep stalks from leaning.
• Planting. Most bulbs/corms can go almost shoulder-to-shoulder—certainly not more than 1 inch apart. Plant so most of bulb is buried, tip just above medium. Soil/sand level start 1 inch below container rim. As bulbs grow, they'll push medium up—glad you allowed expansion. If growing in soil, fertilize once with half-strength liquid fertilizer when brought indoors.