Form:Plants large and small have various forms, each offering something different to the landscape. They can be weeping, round, pyramidal, spreading, oval, vase or columnar. Look at trees for example. In addition to a tree's form during the growing season, consider how much shade it will provide and where the shade will be during the spring and summer. If it's a deciduous tree, imagine how it will look without leaves in fall and winter.
Line: Whether curved or straight, lines are used to draw your eye towards a focal point or to separate areas of the garden. Establishing bed lines is one of the first things to do when designing a landscape.
Texture: Leaves, flowers, stems all have texture. Finding plants and features that contrast or complement is basic to a good garden design. Foliage that is lacy in appearance would highlight a plant with more rounded leaves. Consider the year-round appearance of your prospective plants.
Color: Color is the most obvious aspect of the landscape and may be the least understood. A well-designed landscape can look good without any color (other than green). Color used wisely will accent your garden, while too much color can appear harsh or grating. When deciding which plants to use, keep color in mind just as you would when painting your home. The house is almost always the dominant feature of your landscape. The color of your plantings should complement your home's color. When choosing flowers, for example, consider the almost infinite combinations of color, the flower and foliage shapes, the timing of blooms and their duration, and the height of the plants. Decide whether you prefer the instant gratification of annuals versus the long-term investment of perennials, or a combination of both.