While Feng Shui typically refers to the built environment rather than the external, outdoor environment, there are no real rules when creating a garden. For a Feng Shui garden, the main consideration is that the landscaping looks good, and that it is in keeping with the rest of the environment, as living in a beautiful, stimulating environment is better than living in an ugly, dull one. It is possible to tell a neighbourhoods Qi (the circulating life energy which the Chinese to be inherent in all things; the balance of positive and negative forms) from the amount of greenery, and the general colour of the area.
There are some general rules to follow, however:
Flowers and colourful plants can be used as long as they fit within the environment and follow the rules of the 5 elements: "Wood produces fire, fire produces earth, earth produces metal, metal produces water, water produces wood." Wood is green, fire is red, earth is tans or yellows, metal is white or gold, water is blue or black. You should avoid using them in a destructive combination such that "wood uproots earth, earth blocks water, water douses fire, fire melts metal, and metal chops wood".
You should also consider the direction in which the house sits. For example, if the house faces north and sits to the south is a Li (the fire trigram) building, and so would benefit from red flowers, but not blue. A house which faces to the west and sits to the east is a Tui (the metal trigram), and so would benefit from a mixture of white and gold, while reds and purples should be avoided. Following these rules of balance can support the house and its occupants. These Feng Shui principles should apply to the trim colour of the house as well.
Two items which should be looked at more carefully are rocks and water. Because both are part of the 5 elements, and are used to remedy certain situations in the greater environment, they must be very carefully placed within your garden environment. Water in the west is not good, however if it is placed in the southwest or east it can assist prosperity. These directions should not be in front of, or behind, your house. If they are, you should employ a qualified Feng Shui practitioner to determine whether the water will have a positive or negative effect.
If you do wish to have a fountain in your garden, it is best not to use an earthen container, as earth blocks water in the cycle of elements. Metallic containers can be used to great effect, as metal strengthens water. With the right balance of flowers and plants surrounding the container, the container can blend in very well with the surrounding environment. For larger ponds or pools, a Feng Shui practitioner should be consulted regarding the positioning.
Rocks should also be placed under guidance of a trained practitioner, as they can also have an effect on the prosperity of a building if placed haphazardly, particularly to the front or back of the structure, hence a practitioner can help determine ideal locations for placement. Feng Shui folklore suggests that a building should have a mountain behind it for support. You can create this mountain in your garden using rocks and earth. However, while this may sound good, it is not true in ever case - every building is different, and so should be judged on a case-by-case basis.
At the end of the day, the goal of Feng Shui is to provide a comfortable and beautiful environment - bear this in mind while landscaping, and your garden should become a joy to behold