In the realm of gardening, instant gratification is an elusive matter. For the most part, nature forces her rhythms on our desires. But find a way to speed up the seasons, and you can nudge spring-flowering tulips to bloom in winter.
Choosing Tulips for Indoors. First, select bulbs suited for forcing indoors. Generally, shorter, more compact varieties like 'Red Riding Hood' and 'Stresa' are better choices than tall varieties. Some taller types such as 'Apricot Beauty', 'Calgary', and 'Gudoshnik' are also good choices.
Shop for bulbs as you would for onions: Choose top-quality bulbs that are large and heavy for their size, and avoid ones that are soft or moldy or whose papery brown outside layer is missing. If you can't pot the bulbs immediately, store them in a mesh or paper bag in a cool (below 65°F) place, ideally in the refrigerator crisper. Never store bulbs in the freezer or with fruits that emit ethylene, a gas that hinders flowering.
Timing. To induce flowering, most tulips require about 14 weeks of temperatures below 48°F followed by 2 to 3 weeks at 60 to 65°F. But some are faster. 'Brilliant Star' and 'Christmas Dream' require only 10 weeks below 48°F. Start these in mid-September, and you will have tulips blooming for the holidays.
For staggered bloom after the New Year, start bulbs as soon as they are available, but no later than early October. It's easier to delay flowering than to speed it up; simply increase the time the planted pots spend below 48°F. Also, if you pot bulbs later in the season, they will flower more quickly. For example, a variety started in October will bloom in 12 weeks, but the same one started in December, having been stored until then in a cool room, could bloom in 8 weeks.
Start with clean clay or plastic pots, and place some shards or wire mesh over the drainage hole to hold in the soil. Place at least 2 inches of moistened soilless potting mix (a combination of peat moss and perlite or vermiculite) in the bottom of the container so that the tops of the bulbs will sit just below the rim of the pot. Gently place the bulbs root end down and cover with soil, leaving the bulb noses slightly exposed.
Place the flatter side of each bulb facing the outside of the pot. Leaves sprout first from this side, and will drape gracefully over the sides of the pot. Plant bulbs more closely than you would in the garden -- as close as possible but not touching.
After planting, add water until it seeps out of the drainage holes. Check the soil periodically, keeping it evenly moist. Label each pot with the variety name and the planting date, and move it to a chilling area. Because the bulbs store all the energy they need for bloom, fertilizing is not necessary.
A chilling period. Depending on the variety, it takes 8 to 16 weeks for the planted bulbs to root. Any dark, relatively moist place that provides steady temperatures between 35 and 48°F (40°F is ideal) is fine. An unheated garage, basement, or refrigerator is perfect. If you live where winter temperatures remain in the 40s, simply place the pots outdoors. If winter temperatures drop below 32°F, protect bulbs from freezing; either mulch them heavily or place them in a trench or cold frame, then insulate them well with a layer of vermiculite topped with peat, hay, or shredded bark.
If you don't have a space that's reliably 48°F or below, try this method: Place the unplanted bulbs in a paper bag in the refrigerator (away from fruits) for six weeks. The ethylene gas naturally produced by ripening fruit can destroy the bud inside the tulip bulb. Pot them in a shallow container filled with moistened, soilless potting mix, and place the pot in a 50 to 55°F, dark room for a month before moving to a sunny 60 to 65°F location for bloom and display.
Forcing. After the bulbs have chilled the appropriate length of time, check the drainage hole for root development. If healthy roots are visible, remove any mulch and transfer the pots to a 50 to 65°F location with bright indirect light for about two weeks. This is the actual forcing period, when the bulbs are induced to flower because of the change from winter to spring. Keep in mind that the sunnier and warmer the location, the shorter the tulips stems will be because the sunlight will induce faster flowering. To stagger bloom times, bring the pots in at two-week intervals.
When shoots are about 2 inches tall, begin regular watering and move pots to a sunny window (68°F) to stimulate flowering. As soon as the buds begin to color, return the pots to indirect light; blossoms last longer in cooler temperatures. Ideally, pots should spend the nights in a cool (60°F) room to increase the length of the bloom time up to about 10 days with the proper care.
Forced tulips rarely flower again, even if planted in the garden. To try your luck, remove the flower head after the petals fade, let the tulips complete their life cycle, then plant outdoors.
Photography by the International Flower Bulb Centre
Article published on June 23, 2008.