Must You Wait Till Fall to Plant Flower Bulbs?

How Bulbs Work

• Every bulb contains an embryonic plant, complete with flowers and enough nutrients to keep it growing, right through next year’s bloom. At that point, the mature plant packs in enough nutrients to nurture the next year’s plant as it develops. The plant sheltered within the bulb's papery covering grows constantly, never going completely dormant. The first task of the bulb when it is planted is to grow sturdy roots that will help gather nutrients from the soil to support its growth and to pack in nutrients for the following year. Some bulbs need a period of cooling to kick-start the sequence of development that leads to bloom. Without this cooling, they may grow foliage but cannot flower.

Spring Planting

• Bulbs that bloom in summer and fall -- lily of the Nile (Agapanthus), hardy from U.S. Department of Agriculture plant hardiness zone 7 to 11, and cannas (Canna), hardy from USDA zone 9 to 11, for example -- are planted in early spring. Planting summer and fall-blooming bulbs in spring fits into their growth cycle and guarantee bloom their first season. Some late spring bloomers, including many lilies (Lilium spp.), many hardy from USDA zone 5 through 10, also bloom if planted in very early spring or late winter. In Mediterranean climate areas, planting can commence as early as late January or early February. In cooler zones, tender bulbs must be lifted in fall and replanted in spring.

Cooling Bulbs

• Some bulbs, such as tulips (Tulipa spp.), hardy from USDA zone 3 to 7, should be planted in fall within their hardiness range, but they need more chilling than occurs in warmer zones. Without chilling, the bulbs exhaust themselves by bloom time and are unable to recover and store nutrients for continued growth, a process called perennialization. They can be grown as annuals in warmer zones if the bulbs are refrigerated until December and then planted. The other option for these bulbs is to lift them after their foliage dies back, refrigerate them, replant them in December and hope some of the bulbs come up again and bloom.

Gift Plant Bulbs

• Holiday or gift plants with bulbs might make the transition to the garden, particularly when they have bloomed at their usual time of year. Spring or fall, plant bulbs as soon as possible after blooms fade. Refrigerate bulbs during the heat of summer and plant them in fall. Bulbs that survive may grow only foliage the first year or bloom at an odd time, but if they manage to produce leaves the first year, they will eventually return to their natural bloom schedule.