Half hardy annuals, on the other hand, can tolerate a light frost but not a hard one, and they are generally planted early in springtime to provide color throughout the spring and early summer. Half hardy annuals, like dianthus, generally start their decline in the heat of the summer, but they can bloom again the autumn.

Tender annuals, on the other hand, cannot tolerate any freezing
temperatures at all. Tender annuals, such as zinnias, impatiens and
 vincas, should not be planted until any danger of frost is gone.

Annuals are most often used as landscape plants, and the colors and varieties of annuals make them ideal for use in the landscape. It is important to remember that most annuals need full sunlight for at least
 four to six hours every day in order to produce the best blooms. There
 are, however, shade tolerant varieties of annuals, such as impatiens,
coleus and begonias, and they can be used in parts of the landscape
 that receive less sunlight.

When selecting planting locations for annuals, it is best to avoid areas where water pools after heavy rain. Pooling water can drown the roots of many annuals. It is also important to avoid planting annuals in areas that are close to trees or large shrubs, since the root structures of these large plants can compete for moisture and leave your annuals without sufficient water.

It is also important to prepare the planting bed properly to get the most from your annuals. The planting bed should be deeply spaded and dug between six and ten inches deep. Clay heavy soils should be amended prior to planting by mixing in at least two inches of humus, leaf mold, compost or small pea gravel. These improvements will help the soil drain well and provide additional aeration as well.