This article records tradition as it has been passed down and reported. Its sources are not yet part of the atlas's verified catalogue.
Wood Branches gathers the two of the twelve Earthly Branches whose own fixed agent is Wood: Yin the Tiger and Mao the Rabbit, the branches that open and then crown the spring.
Yin, the third branch, opens the first solar month at the Start of Spring in early February and governs the hour from three to five in the morning, in the east-northeast. It is a growth branch, storing Jia as its principal qi alongside Bing and Wu, so Yin carries the newborn Fire of the year concealed inside its own Wood; as the branch that opens the Fire trine, it marks the vigorous upthrust where the year's yang first breaks into the open. Mao, the fourth branch, sits at the spring equinox and governs the hour from five to seven in the morning, seated due east. It is a pure cardinal branch, storing only Yi, so its concealed qi and its surface agree without the mixed stems a storehouse branch carries; as the cardinal Wood it anchors the Wood trine it forms together with Hai and Wei, and it reads in the Four Pillars as clean, undiluted Wood.
Between them the two Wood branches trace spring's whole arc, from the first upthrust of yang Yin carries, fire already seeded within it, to the gentle, supple growth Mao brings to its height. Both began, like every branch, as day-count signs in the oracle-bone tradition, numbering a sixty-day cycle together with the ten Heavenly Stems before either carried the animal now attached to it.