By Vera Gates
There are two basic options: symmetrical and asymmetrical. The site itself, the architecture and the design intentions will inform which you will choose.
A symmetrical design is created around a central axis line, with everything on one side of the axis being mirrored exactly on the other. This works great if you have a symmetrical space and the architecture of the house is laid out in a symmetrical way. It can also work well if there is one great natural feature of the site, for example a perfectly matched pair of trees, that can be the central, ordering focus of the design.
Symmetrical design is the easiest to draw on paper and the most difficult to maintain long term in the garden. While it works very well for buildings, it can very difficult to mirror plantings from one side of a garden space to another, especially if sun and shade vary, the plants on one side will perform very differently than the other and throw off the planned symmetrical design. Because of this it is best to rely on built elements to maintain the symmetry, versus plantings.
The site will either lend itself to a symmetrical design or it won't. If the space is very regular and aligned to key site lines, a symmetrical design can work well.
It can be very difficult to incorporate existing natural features and often a symmetrical garden design requires removing just about everything on the site. This is not a problem if the site has already been cleared, but can be very costly otherwise.
The rhythm of a symmetrical garden is easily recognized and understood, but can quickly become repetitive and boring, especially if it goes on for too long. A better approach is to incorporate some symmetrical aspects, where they make the most sense and then interweave that symmetry with other aspects, as shown below.