General concepts

Hidden stems (Cang Gan)

Also known as: hidden stemscang gancanggan藏干支藏干hidden heavenly stemsbranch hidden stemsren yuan人元main qiben qi本气middle qizhong qi中气residual qiyu qi余气jijanggan지장간zokanzoukan蔵干

Hidden stems (Cang Gan, 藏干) are the Heavenly Stems that the BaZi tradition places inside each of the twelve Earthly Branches: one to three per branch, a main qi and sometimes a middle and a residual qi. They let a chart show phases that its visible signs do not.

A BaZi chart has eight visible characters: four Heavenly Stems on top and four Earthly Branches below them. The tradition reads each stem as a single, pure phase. The branches are more complex. Each one stands for a month and a moment in the seasons, and the classical texts describe it as holding several kinds of qi at once, written as stems hidden inside it. They are called Cang Gan, "stored stems", and sometimes Ren Yuan (人元), the "human element", because they sit between heaven above and earth below.

Each branch holds one to three of them. The main qi (ben qi, 本气) is the strongest and gives the branch its phase. The middle qi (zhong qi, 中气) and the residual qi (yu qi, 余气) are weaker; one is usually read as what remains of the previous season, the other as what the branch stores or prepares. The common table is: Zi (子) holds Gui; Chou (丑) holds Ji, Gui and Xin; Yin (寅) holds Jia, Bing and Wu; Mao (卯) holds Yi; Chen (辰) holds Wu, Yi and Gui; Si (巳) holds Bing, Wu and Geng; Wu (午) holds Ding and Ji; Wei (未) holds Ji, Ding and Yi; Shen (申) holds Geng, Ren and Wu; You (酉) holds Xin; Xu (戌) holds Wu, Xin and Ding; Hai (亥) holds Ren and Jia. The main qi is always listed first.

The pattern follows the seasons. The four branches in the middle of a season, Zi, Mao, Wu and You, are nearly pure and hold a single stem, or two in the case of Wu. The four Earth branches at the turns of the seasons, Chou, Chen, Wei and Xu, keep a trace of the season that is ending and are called storehouses of another phase: Chen stores Water, Wei stores Wood, Xu stores Fire and Chou stores Metal. The four branches that open a season, Yin, Si, Shen and Hai, carry the seed of the phase that will come next.

In a reading the hidden stems matter in three ways. They are roots: a stem on top of a pillar is read as rooted when its phase is also hidden in a branch, and many schools judge the Day Master's strength largely by these roots. They receive Ten Gods: each hidden stem relates to the Day Master like a visible one, so a chart can contain, for example, a Direct Officer that appears only inside a branch. And they can be revealed (tou chu, 透出) when the same stem also stands visibly on top of a pillar, which the tradition reads as an emphasis. Schools weigh the three levels differently; some give the main, middle and residual qi a share of days within the month (Ren Yuan Si Ling), and published tables differ in details, for example whether the Horse also holds Ji.

The free BaZi calculator in AstroSensus uses the common table above. Under every branch it lists the hidden stems, main qi first, each with its character, phase and Ten God towards the Day Master. In the five-phase overview the hidden stems are counted separately from the eight visible signs, and both numbers are labelled as counts, not strength. The calculator does not weigh the hidden stems, does not mark which of them are revealed and does not judge whether the Day Master is strong or weak.