The main reason to grow annuals in a bed by themselves is that the entire bed can be dug up and replanted once or twice a year. The presence of perennial plants makes this task more difficult. However, combination beds have their appeal, and annuals can be tucked into almost any sort of bed for temporary color or interest.
Some of the favorite combinations with annuals are annuals with perennials or annuals and spring-flowering bulbs in the same bed. Both perennials and bulbs put on a spectacular show of blossoms—often in colors or forms not found in annuals. By combining the three, then, you not only lengthen the overall period of bloom but also create a scene rich in contrasting flower and foliage forms and expand the possibilities for color combinations.
By adding a few evergreen or deciduous shrubs to the back of the border, you can create a scene with something of interest in every season. Look for shrubs that bloom during periods when little else is flowering in the garden; early-blooming flowering quince and forsythia are good examples.
If you live in an area where winter brings a blanket of snow, choose shrubs or trees with appealing winter form or color, such as the birches or dogwoods, or those with fruit that stays on the branches late into the season, such as cotoneasters, crabapples, or firethorns. Some gardeners like an even-textured “wall” behind their beds or borders. For this effect, consider installing a formal hedge instead of a fence or planting a not-so-formal grouping of leafy evergreen or deciduous shrubs.
In recent years “potpourri” gardens have increased in popularity. In the style of the European kitchen gardens, these are working gardens that combine annuals, perennials, herbs, bulbs, vegetables, and even fruit trees. Although they are usually the practical result of trying to grow as many plants as possible in a limited space, the results can be as attractive as they are productive.