A recent caller left a message on my phone mail: "I try every year but I don't have any luck ... how can I force tulips?"
"Force them to do what?" That was my initial reaction because tulips are like cats - it's hard to force them to do anything. You have to make them want to bloom indoors, and the way to do that is to fool them into believing spring has already sprung. Tulip bulbs have to chill out (chillax?) in cold storage for 12 to 16 weeks and be kept in the dark before they'll send up shoots. A fridge, the garage, a root cellar or even outdoors (under the right conditions) work fine.
Tulips are not all alike.
Another trick in forcing tulips is to choose the right type of bulbs for the job, including favorites like Darwin hybrids, especially the "Impression" series that comes in red, pink and apricot. Other good choices are Truimphs, available in a range of saturated colors as well as bi-colors, and some of the single and double-early tulips. Always choose unblemished, firm bulbs.
You can chill the bulbs in the old-fashioned way by potting them up and placing the pots in cold storage (40 to 45 F). An easier method, especially if space is limited, is to place the bulbs themselves in the fridge for the big chill, them planting in pots.
Forcing now means the blooms should break in late February or early March.
Whichever way you go, you'll need good quality potting soil and clean containers with drainage holes in the bottom.
Old-fashioned forcing: Partially fill containers with potting soil. Arrange tulip bulbs on top of the soil so the flat side of the bulb is facing toward the sides of the pot. Tops should be even or slightly below the edge of the container. Rule of thumb: 4 to 5 bulbs for 5-inch pots; 6 to 7 bulbs for 6-inch pots, 8 to 10 bulbs for 8-inch pots - you get the idea. Cover bulbs with potting soil, allowing the tops to poke out above the soil. Label the containers with the variety name and planting date, then water the containers.
Place the pots in cold storage in total darkness for 12 to 16 weeks, watering regularly. You can cover the pots with plastic bags if you like; just remember to punch a few holes in the bags. If you're using the garage, put a cardboard box over top of the pots to keep out light. Remove the pots from cold storage when yellow shoots appear. Place the tulips in a low-light location where the temperature is 50 to 60 F. Shoots will turn green in about a week, then you can move the bulbs into a light space where temperatures are 60 to 70 F. Don't forget to water the bulbs and turn the pots regularly for straight growth. Flowering should begin in three to four weeks after the bulbs come in out of the cold. Keep 'em coming by removing pots from cold storage at every other week.
Newfangled forcing: Place tulip bulbs in a brown paper or mesh bag, then tuck the bag into the refrigerator vegetable crisper for seven or eight weeks. And it's OK if you forget about them for up to 14 weeks (out of sight is out of mind ...). This chilling method will work if you don't keep fruit in the fridge. Fruit produces ethylene gas as it ripens and that will kill the flower inside the bulb. After the cold period, pot the bulbs as suggested in the old-fashioned way, then place the pots in a 50-55 F dark area for a month. Increase the light and temperature levels. Continue watering and wait for the blooms to appear. You'll be amazed at how it will lift your spirits to see those blooms.
Cold-frame or trench method: You can give tulip bulbs the cold shoulder by burying the pots outdoors beneath 10 inches of soil, followed by 10 inches of mulch such as hay or leaves. The key is not allowing the bulbs to freeze. Mark your calendar (and the spot!) to go outdoors, uncover the pots and bring them indoors to begin the forcing process.
Whichever method you choose, don't let the potted bulbs dry out. After forcing, tulip bulbs are spent and can't be replanted in the garden.