As a general rule, bulbs should be planted at a depth about 2.5 or 3 times their height. In other words, if a tulip bulb is 2 inches tall, you should dig a hole about 5 to 6 inches deep for it. Planting too shallow may expose the bulb to cold winter temperatures while planting too deep can force the plant to push its way up through too much soil resulting in a weakened plant.

A. Planting Spring Flowering Bulbs - Tulips, daffodils, hyacinths and other bulb plants that bloom in the early spring will need to be planted in the autumn of the year. Most of them need to be exposed to a certain number of days of temperatures below 40 degrees before they will develop the precursors of stems and flower buds. If they do not get these conditions, they will not flower the next spring. Check with your local Extension Service office or local nurseries to see if this is a problem in your area. Some regions of the Southern United States do not receive enough cold to trigger flowering in these bulbs.

B. Summer Flowering Bulbs - As mentioned earlier, there are a whole bunch of different types of plants that are lumped into the category of "bulbs." Several true bulbs such as the hardy lilies (Lilium) or ornamental onions (Allium) need to be planted in the fall since they too need a chilling effect before they will bloom.

Many of the other so-called bulbs that bloom in the summer including cannas, gladiolus, tuberous begonias, caladium and dahlias may be planted in the spring. In fact, these types of plants are generally not hardy in northern gardens and will need to be dug up and stored each autumn. Many of them may even be purchased in the spring as container plants which have been grown in the greenhouse.