AMES, Iowa – Tulips, a favorite in the garden, are known as harbingers of spring. Their beautiful flowers and vibrant colors are a refreshing change after a cold and dreary winter – but they also can be forced to bloom indoors for pre-spring enjoyment. Iowa State University Extension and Outreach horticulturalists share tulip planting tips for indoor and outdoor flowers. To have additional plant and garden questions answered, contact the ISU Hortline at 515-294-3108 or firstname.lastname@example.org.
October is the ideal time to plant tulips, daffodils and other spring-flowering bulbs in Iowa. When planted in October, spring-flowering bulbs have sufficient time to develop a good root system before the ground freezes in winter. If the ground isn’t frozen, tulips and other spring-flowering bulbs can be planted as late as late November and early December.
Tulips perform best in partial to full sun. Planting sites should receive at least six hours of direct sun per day. Tulip bulbs also need a well-drained, fertile soil.
Plant spring-flowering bulbs at a depth equal to three to four times their maximum bulb diameter. Accordingly, large bulbs, such as tulips and daffodils, should be planted 6 to 8 inches deep. Plant smaller bulbs, such as crocuses and grape hyacinths, 3 to 4 inches deep. Space tulips and daffodils 6 inches apart. A 3-inch-spacing is adequate for crocuses, grape hyacinths and other small bulbs.
Most modern tulip varieties bloom well for only three or four years. However, there are some tulip types (classes) that bloom well over a longer time period.
Darwin hybrid tulips are generally the longest blooming hybrid tulip. Darwin hybrid tulips are prized for their large, brilliant flowers. Flowers are available in shades of red, pink, orange, yellow and white. Blooms are borne on stems that are up to 30 inches tall. Darwin hybrid tulips bloom in mid-season.
Fosteriana tulips also perennialize well. They are noted for their large, elongated flowers. Flowers appear in early spring on 10- to 20-inch-tall stems. Foliage is typically green or gray-green. However, a few varieties have mottled or striped foliage. Fosteriana tulips are also known as Emperor tulips.
Species tulips are generally the longest lived tulips. Some naturalize when given favorable growing conditions. Species tulips include wild tulip species and varieties developed from these wild species. Species tulips are usually smaller than most modern tulips. They also have smaller flowers. Species tulips are excellent choices for rock gardens and in the front of beds and borders. They are also sometimes referred to as botanical tulips.
To successfully force tulip bulbs indoors, you’ll need high quality bulbs, a well-drained commercial potting mix, and suitable containers. Containers for forcing can be plastic, clay, ceramic or metal. Almost any container can be used as long as it has drainage holes in the bottom.
Begin by partially filling the container with potting soil. Then place the tulip bulbs on the soil surface. Adjust the soil level until the tops of the bulbs are even or slightly below the rim of the container. The number of bulbs to plant per pot depends on the size of the container. Generally, four to five bulbs are placed in a 5-inch-diameter pot, six to seven in a 6-inch-diameter pot. When placing tulip bulbs in the container, position the bulb so the flat side of the bulb faces the wall of the pot. When positioned in this way, the large lower leaf of each bulb will grow outward over the edge of the container forming an attractive border around the edge of the pot.
Once properly positioned, place additional potting soil around the bulbs. However, do not completely cover the bulbs. Allow the bulb tops (noses) to stick above the potting soil. For ease of watering, the level of the soil mix should be ½ to 1 inch below the rim of the container. Label each container as it is planted. Include the name of the variety and the planting date. After potting, water each container thoroughly.
In order to bloom, tulips and other spring-flowering bulbs must be exposed to temperatures of 40 to 45 degrees Fahrenheit for 12 to 16 weeks. Possible storage sites include the refrigerator, root cellar or an outdoor trench. During cold storage, water the bulbs regularly and keep them in complete darkness.
Begin to remove the potted tulip bulbs from cold storage once the cold requirement has been met. At this time, yellow shoots should have begun to emerge from the bulbs. Place the tulips in a cool (50 to 60 degree Fahrenheit) location that receives low to medium light. Leave them in this area until the shoots turn green, usually four or five days. Then move them to a brightly lit, 60 to 70 degree Fahrenheit location. Keep the plants well watered. Turn the containers regularly to promote straight, upright growth. On average, flowering should occur three to four weeks after the bulbs have been removed from cold storage. For a succession of bloom indoors, remove pots from cold storage every two weeks.