Some caution is required when growing tulips indoors. Like many spring bulbs, tulips contain alkaloid compounds that are moderately toxic to pets and to humans. The bulbs contain the highest concentration of toxins, but trace amounts are also found in flowers and leaves. Consumption of entire bulbs most often causes intestinal irritation. In addition, humans who handle bulbs often may develop skin sensitivity and allergic reactions. However, fatal reactions in humans or pets are very unlikely. The typical method is to pot the bulbs about October 1, then put the planted pots into chilled conditions for three or four months before bringing them out into warmer, sunnier conditions to sprout and bloom. By timing the chilling period carefully, you can force tulips to bloom at a time of your choosing. Normally, tulips will bloom about 17 to 22 weeks after you begin the chilling period on the bulbs—12 to 16 weeks for chilling, about a week for sprouts to appear, then another four or five weeks until they reach full bloom. Gardeners who want Valentine’s Day blooms, for example, might begin chilling the bulbs in early October.
How to Grow Tulips Indoors
Sunlight
During the chilling period, potted tulips need to be kept in the dark. When you take them out of chilling, keep them in dark conditions for four or five days until sprouts appear. Then, move the pots into brighter, warmer conditions until the plants begin to flower, which normally takes four or five weeks. Once in full flower, they are best moved to a spot with slightly less intense sunlight, which will preserve the blooms longer.
Temperature and Humidity
Careful control of temperature is essential for getting tulip bulbs to bloom indoors. First, the potted bulbs need to undergo a chilling period at 40 to 45 degrees Fahrenheit for 12 to 16 weeks. Move the pots out of their chill conditions five or six weeks before the anticipated bloom. For the first four or five days, keep them in relatively cool and dark conditions until sprouts appear, then move them into a warmer, sunnier location until they begin to flower. About 65 degrees Fahrenheit is an ideal temperature for flowering tulips. Should you want to save the bulbs and attempt to reuse them after blooming is complete, dig out the bulbs, brush off the soil, and store them in a relatively warm, dry location until outdoor planting time—which is normally the following fall.
Watering
Water the bulbs thoroughly immediately after planting, then whenever the soil begins to feel dry to the touch. Do not allow tulip bulbs to dry out completely until after the blooms have faded.
Fertilizer
Tulip bulbs forced indoors usually require no feeding since they are usually discarded after blooming. However, if you want to try reusing the bulbs in the outdoor garden after the indoor forced blooms are done, it’s best to give the growing plants some bulb fertilizer to restore energy to the bulbs.
Pruning and Maintenance
No maintenance is really necessary with forced bulbs, but if you want to try reusing the bulbs, allow the foliage to continue growing in full sun as long as possible, until it turns yellow and dries up. At this point, dig out the bulbs and store them in a warm, dry location until outdoor planting time.
Container and Size
A pot with a wide, flat bottom works best for tulips since it’s not likely to tip over when the tulips get top-heavy with blooms. The pot should be 6 to 8 inches deep, with a tray or saucer to catch water. Ceramic, clay, plastic, or metal pots can all work for growing indoor tulips.
Potting Soil and Drainage
Ordinary potting soil or well-decayed compost is ideal for growing tulip bulbs in indoor pots. The pot should have good drainage holes,
Potting and Repotting Tulips
Fill the container half full of potting soil or compost, then position the bulbs onto the soil with the pointed side up. Place the bulbs no more than 2 inches apart for the best display. Some gardeners recommend planting tulip bulbs with the flat side facing the sides of the container, which causes the foliage to spill over the sides of the pot as the plants grow. Cover the bulbs with potting soil to within 1/4 inch of the rim and water thoroughly before putting the pot into chill storage.
