When tulips (Tulipa spp.) bloom in early to late spring, the garden comes to life with bold color. Tulips are cold-climate perennials not naturally well suited for mild climates, but, by pre-treating the bulbs before planting, you can grow a striking tulip garden in Mediterranean climates and frost-free coastal areas. Tulips are perennials in U.S. Department of Agriculture plant hardiness zones 3 through 8 and are grown as cool-season annuals in warmer areas.
Tulip Divisions or Groups
Tulips are divided into 15 groups, or divisions. Within each group, there are a variety of species and cultivars that bloom in red, yellow, white, green, pink, salmon, purple and lavender. Some tulip groups bloom in early spring, while others bloom in mid or late spring. Plant a selection from each group to create garden full of blooming tulips through the blooming season.
Tulip Groups by Bloom Time
Early to mid spring blooming tulip groups are: Single Early Group, Double Early Group, the Kaufmanniana Group and the Greigii Group. Mid to late spring blooming tulip groups are: Triumph Group, Darwin Hybrid Group, Lily-Flowered Group, Fringed Group and the Fosteriana Group. Late spring blooming tulip groups include Single Late Group, Viridiflora Group, Parrot Group and the Double Late Group. There is also a division listed as Miscellaneous Group, containing a variety of tulips and hybrid varieties, and the no longer available Rembrandt Group.
Getting Tulips to Bloom
Tulips bloom in spring, but preparation begins in early to late winter. Tulip bulbs need a minimum of four weeks of chilling before they will bloom. Nurseries often sell pre-chilled bulbs but if not, the process is simple. Start the chilling process in late fall, around late October or early November, in USDA zones 9 and warmer. To chill tulip bulbs, pack them in a box or bucket and keep them between 32 and 50 degrees Fahrenheit for four to eight weeks.
In USDA zone 8, plant tulip bulbs directly in the soil in late fall without pre-chilling them. The cool winter weather will naturally provide the required chilling time required for a strong spring blooming season. In USDA zones 9 and warmer, plant tulips in December after chilling the bulbs for the four- to eight-week period. Tulip bulbs grow best planted 4 to 6 inches deep and 2 to 5 inches apart.
You can force tulips to bloom out of season in winter by pre-chilling the bulbs and then planting them in pots indoors. The bulbs require the chilling period followed by 10 to 16 weeks in warm conditions before they will bloom. Start chilling the bulbs in late summer or early fall. After the chilling period, plant the tulips in pots and keep them at 65 F for two weeks, then increase the temperature to 68 F for the rest of the growing period.
- Missouri Botanical Garden: Tulipa (Group)
- Seasonal Celebrations: Seasonal Planting Calendar
- University of California Statewide Integrated Pest Management Program: Tulip--Tulipa spp.)
- University of California Marin Master Gardeners: Plant Bulbs Now for Spring Beauty
- National Gardening Association: How-To Project: Forcing Tulips Indoors
- Royal Horticulture Society: Tulips
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