The best time to plant spring-flowering bulbs depends on where you live. Ideally, wait until the soil temperature is below 60Â°F. As a general guide, plant in September through early October if you live in USDA Hardiness Zones 4 or 5; October to early November in zones 6 or 7; and November to early December in zones 8 and 9. Plant bulbs that have been refrigerated for 8 to 10 weeks in late December to early January in zone 10.
Bulbs grow best in a location with full sun. Choose planting beds where bulb foliage will receive at least 6 hours of sun during spring through summer. Most bulb species also prefer well-drained, not soggy, soil.
Dig Holes. Dig individual bulb holes or one wide hole to plant groups of bulbs. Digging up the whole bed makes bulb spacing, layering, and soil amending easier. The depth of the hole should equal three to four times the bulb height. For example, dig a 6- to 8-inch-deep hole for a 2-inch-high bulb.
Arrange bulbs. Set the bulbs in a planting bed or in separate planting holes with their roots or basal plate downward. Space bulbs according to supplier's recommendations. In general, smaller bulbs are planted closer together than larger bulbs. Fill the planting hole with soil and firm it gently.
Water and mulch. Water the bulbs right after planting to help initiate growth. In mild-winter areas, mulch right after planting to help keep soil cool and moist. Apply mulch after soil freezes in cold-winter areas to prevent the ground from heaving during winter thaws and pushing the bulbs too close to the surface.
Fertilize. Each autumn, maintain existing tulip and hyacinth plantings by sprinkling 1/2 cup of the 9-9-6 fertilizer per 10 square feet. Daffodils and snowdrops thrive on a 5-10-20 mixture. Three-fourths cup of 5-10-12 mix per 10 square feet works on any type of bulb. First-year bulbs don't need fertilizer.
Plant "mild-winter" tulip species that thrive in zones 8 through 10, such as the lady tulip (T. clusiana), the Candia tulip (T. saxatilis), and the Florentine tulip (T. sylvestris). These tulips do not need chilling before planting.
To discourage voles or gophers, add a handful of sharp gravel to the planting hole or plant bulbs in wire or fabric baskets. Don't mulch where rodents are a problem.
Layer two different species, such as tulips and grape hyacinths, in the same bed for exciting color combinations. Plant tulips first, then add enough soil to achieve the proper depth for the grape hyacinths. Plant the grape hyacinths between the tulips.