The concept of Wood includes all forms of vegetation, from trees to flowers to grasses, but the tree is the archetypal representation. Consider an oak tree and its early manifestation, the acorn. In the autumn, leaves and acorns fall to the earth and some acorns become buried. During the winter the acorn, the seed, lies dormant in the ground. In response to the increasing yang of warmth and light in springtime, the acorn begins to sprout. It also requires moisture, sufficient soil and trace minerals in order to achieve its potential growth.

At this stage, the acorn has a plan within it. It is destined to be an oak or nothing at all. The young plant grows and encounters impediments such as rocks or nearby trees which frustrate it. It does not back off and consider giving up. It pushes upward but it is also prepared to change shape in order to maximise its growth. All the while it is forming itself, stage by stage, into an oak tree – the best, given the circumstances, that the acorn could have created.

People also begin life with an internal map or plan as to their capabilities and direction. They strive to become their own form of tree and they encounter obstacles and frustrations along the way. Depending upon the nature of their Wood, they may show flexibility in the face of these obstacles, thereby continuing to grow and develop. Alternatively they may have difficulty adapting and consequently become stuck. Like trees, people also require certain resources to fulfil their potential and they also require flexibility in order to adapt to changing circumstances.

For people the hindrances are often environments hostile to their growth. For example, a child with the talents of a mathematician may attend a school that supports drama and sports and has no committed maths teacher. Just as the oak requires resources, people require situations where their capabilities and directions are accepted, nourished and respected. Most of us know when we are not in the right environment, such as in the right school or doing the right work. Like the growing tree, our growth is frustrated and we need either to push harder or search out another context in which we are better able to thrive. The growing oak cannot pull up roots and transfer to a different field or meadow. Humans, however, frequently search out environments where the structures and resources available support their desire to grow and develop.

Although trees are the most obvious, any member of the plant world represents Wood. There are over 200 species of trees. Algae, lichens, moss, ferns, flowers and fungi all have a developmental cycle of growth in which maturity has a recognisable form at the end stage. Many plants (although not all) are green. They are usually rooted in the earth and respond to cyclical changes in the seasons. When acupuncture was developing, China was an agrarian society and doctors would have been well aware of the growth cycle of plants and what was required for them to flourish. Plant life provided many metaphors for early Chinese thinkers in their attempts to understand the human condition (Allan, 1997).

A fire needs fuel in order to burn well. In ancient times this fuel was usually the wood gathered from nearby forests. That Wood is the mother of Fire means that Fire symptoms, for example, heart pains, might be caused by one of the Organs of the Wood Element. When a symptom is manifesting from the Organ of one Element, it is always wise to look at the state of the qi of the previous Element. This is the ‘mother’ Element along the sheng cycle. An example of this is that Wood CFs can easily have heart problems arising from anger.

Water is the ‘mother’ of Wood in the sheng cycle. It is easy to understand how Water can create Wood, as plants will not survive unless they are given enough moisture. Sometimes when patients manifest symptoms that appear to be connected to the Wood Element these are caused by imbalance in the Water Element, the mother. Treating the mother causes the symptoms to improve.

Wood controls Earth across the ke cycle. If this relationship becomes dysfunctional it can easily create a wide range of symptoms. Physically there may be a tendency to digestive symptoms but it can as easily produce problems in patients’ minds and spirits, especially in the relationship between their need for sympathy and their anger. For example, a patient may appear to be frustrated and angry but really be crying out for support and sympathy. Once the person feels supported the anger may lessen.

The Metal Element controls the Wood Element. This is often described metaphorically with an example of a metal saw cutting down a tree. If a person’s Metal Element becomes weak it can lose control of the Wood Element. The Wood Element in turn may become too strong and symptoms of fullness such as extreme anger and hostility may develop.