Small trees, dwarf conifers, and deciduous or evergreen shrubs are combined with dense plantings of suitable perennials and bulbs, to form a harmonious plant community. Annuals and climbers may also be included. The trees and shrubs provide the structure and vertical elements of the border. Perennials, ornamental grasses, and ground covers furnish flower color, later season interest, and the ground layer. The focus is not just on color, but also texture and shape of plants and garden features. Both harmony and contrast, and the balance of the two in a planting, are essential. Dwarf, columnar conifers, and garden ornaments can be focal points. Ideally, mixed borders promote year-round interest, but may favor one season, such as summer or fall. Certain plants are repeated throughout the planting area or even the complete garden, and several varieties are used in larger drifts or sweeps. This results in visual continuity and moves the eye along the border. The plantings can display an analogous color range, favoring just a few related colors, or present a rainbow of colors, expressed in a polychromatic, joyful color scheme.

Mixed borders are spectacular to look at and provide interest throughout the year, and can also be low-maintenance if designed correctly. While dead-heading is important to prolong the flowering season, choosing long-flowering, robust plants with improved pest and disease resistance will ease maintenance requirements. If the soil has been amended and prepared thoroughly prior to planting, the plants will form a solid, continuous plant community within two years of installation, resulting in reduced weed growth and water loss. “Soil wants to cover itself” to prevent moisture loss and provide an environment beneficial to the soil food web. Well-designed mixed borders densely cover the soil during the growing season, resulting in a happy soil life and year-round enjoyment for the gardener and viewer.

The plantings frequently are informal and can be naturalistic. While this is a decorative, attractive garden style, and appropriate for the avid gardener, it can be quite high maintenance, especially if self-seeding flowering plants are included. A combination of mixed border, in conjunction with a decorative vegetable garden or potager, is similar in style, but lower in maintenance and may look less busy.