Planting Location Before selecting the location to plant bulbs in the landscape, consider the light requirements of the plant. Since early spring bulbs bloom before most trees or shrubs leaf out, they can successfully be planted under trees and shrubs. Many summer blooming bulbs require full sun or partial shade. Spring bulbs planted on a south slope will bloom earlier than the same bulbs planted on a north slope. Spring bulbs planted on a hillside will bloom earlier than bulbs planted in a valley.
Cold air is heavier than warm air and behaves like water.
It flows down the slope, settling in the low areas. The general rule of thumb for planting spring bulbs is to plant two to three times as deep as the bulbs is tall. This means most large bulbs like tulips or daffodils will be planted about 8 inches deep while smaller bulbs will be planted 3-4 inches deep. Planting depth is measured from the bottom of the bulb. This rule of thumb on planting depth does not apply to summer bulbs which have varied planting requirements.