How-To Project: Forcing Tulips Indoors
by National Gardening Association Editors
For those who can never get enough of tulips or can't wait until they spring up naturally in the garden, they can be forced indoors. To "force" a bulb means to create an environment where the bulb grows when it naturally wouldn't. By following these steps, you can buy tulip bulbs when they're available in fall and force them to bloom for the holidays or any time during the winter.
Tools and Materials
- Clay or plastic pots
- Soilless potting mix
- Tulip bulbs
- Hose or watering can
Choose the right varieties. In general, shorter-growing varieties such as the species Tulipa humilis (or the very similar T. puchella) are the easiest to force indoors. But 'Apricot Beauty' is a good example of a taller variety that forces well. Select large, firm bulbs, avoiding soft smaller-sized ones, and store them in a cool place until you're ready to force them.
Plant at the right time. You can start forcing tulips in October for blooms by Christmas, or later in fall for blooms by midwinter. Generally, tulips need at least 12 to 16 weeks to bloom if started in September or October, but only 8 to 10 weeks if started in December.
Tulips grow best in clay pots, which dry out faster than plastic pots. Choose a deeper pot for tall varieties, a shallower one for shorter kinds. Be sure the pots have drainage holes in the bottom. Partially fill the pot with moistened soilless potting mix.
Use as many bulbs as can fit in the pot without touching. The more in the pot, the more dramatic the flower show. Place the bulbs root end down so their tops sit just below the rim of the pot. Cover them with enough soil so that only the bulb noses are showing. Water well. Label with the variety and planting date.
Chill bulbs. Before tulips will sprout and produce flowers, they need a chilling period to simulate winter. Without this period, the bulbs won't grow or won't produce a good-quality flower. You can simulate winter by placing the potted bulbs at 32 degrees F to 50 degrees F in a dark area such as an unheated garage or basement. A refrigerator crisper works well, but never put them next to fruits such as apples that emit ethylene, a gas that hinders flowering. In warm areas, you can even leave them outdoors as long as the temperature doesn't go below freezing or above 50 degrees F . Just keep the pots moist. Depending on the variety and planting time, they'll need 8 to 16 weeks of chilling. Check the drainage holes for root development and look for bulb sprouts starting to grow as signs they've had enough chilling.
If you don't have room for all the planted pots, try placing the unplanted bulbs in a paper bag in the refrigerator crisper for six weeks (always without fruit in the refrigerator at the same time), then pot them and place them in a 55 degree F dark room for a month. Then bring them into a 65 degree F room to grow and flower.
Forcing bulbs to flower. Bring the chilled pots into a 50 degree F to 65 degree F room with bright, indirect light for about two weeks. The warmer the temperature, the shorter the flowering stems and faster the bulbs will flower. When the bulb shoots are 2 inches tall, move the pots to a sunny 68 degree F location. They'll flower within a week or so. The cooler the temperatures (60 degrees F is ideal at night), the longer the flowers will last.
Once tulips have finished flowering, you can throw them into the compost or cut back the flowering stem and let the leaves die back naturally.
To prevent the potting mix from leaching out the drainage hole when watering the container, place a piece of window screen in the base of the pot before adding the potting mix. This allows the water to drain but keeps the potting mix in the pot.