There are many schools and approaches to Feng Shui, but my training is in Form School which is rooted in the earliest origins of Feng Shui. The form school practitioner is one who looks first at land formations and applies those guiding principles to both the exterior and interior of a home.
You may think that what is going on outside the home is irrelevant but it is the first place I look to asses the situation. A Feng Shui practitioner can learn a great deal about what may be happening inside the home by looking at the land form where the house is sited and by the type and quality of the vegetation that surrounds it.
Some of the most helpful signs are those given by trees. Different trees prefer different types of energies, seeing what kinds of trees thrive or fail to thrive can tell me what is happening in the earth that could effect the dwelling. Oak trees could indicate Geopathic Stress, Willow trees thrive in wet soil and could indicate a wet basement or mold problems. Multiple burls or "tree cancers" or trees that are growing in odd ways can again indicate Geopahtic stress or other electromagnetic stress. Correcting the underlying energetic problems are a critical foundation for any subsequent adjustments that need to be made and without them the other adjustments or "cures" will be less effective.
By dowsing I can confirm these presence of these energies but the trees are always offer great insight into the energy of the land. Of course newer construction areas where all of the trees have been cut down make this much harder. So, take care of our green friends because they made hold the clues that will in turn help us!
Below are a few examples of what trees can tell us:
This is a very large, old, Weeping Willow tree, one of my favorites. It is thriving because there is a great deal of water in the ground around it, the presence of multiple large tree cancers or burls also indicates the presence of Geopathic Stress.
The oddly curved trees shown among this group of trees shows the negative effects of electromagnetic fields and are growing below large power lines.
This tree in the foreground is growing away from geopathic stress because it does not like this type of energy, you can see the oak tree behind it thrives in these conditions and is straight, tall and strong.