Wood Release

is a combined nature transformation kekkei genkai made up of techniques that mix earth-based chakra in one hand and water-based chakra in the other to create wood as well as various plants, from simple seeds to even flowering trees. Wood and plants can be produced from any surface, including the user's own body, as the user's chakra is literally converted into a source of life. are commonly affiliated with the Snake seal.

Overview
While being a kekkei genkai, the use of this nature transformation has only been done by Hashirama Senju and those who possess his exact DNA. His ability to use this technique was one of the reasons he was given the title of the First Hokage, and with Wood Release Secret Technique: Nativity of a World of Trees he created the foundation of Konohagakure. This technique also allowed him to completely reshape battlefields to his advantage. A highly coveted ability, several people have tried to replicate his power, with a few achieving weaker versions of it through experimentation with Hashirama's cells. As Obito Uchiha noted, Wood Release is very hard to control due to the sheer life force within Hashirama's cells, which can potentially overwhelm any who are infused with them. Danzō Shimura demonstrated this when, after his chakra levels were depleted, he almost turned into a tree as the cells overpowered him.

A derived technique of the Wood Release is the Hokage-Style Sixty-Year-Old Technique — Kakuan Entering Society with Bliss-Bringing Hands. This technique produces a seal on the user's right hand that can suppress a tailed beast's chakra as well as its influence over its jinchūriki. Hashirama's necklace aided in this technique's execution, but its exact purpose was unclear. After Naruto Uzumaki destroyed the necklace, Yamato implied that he could no longer suppress the Nine-Tailed Demon Fox's influence. Nevertheless, when Naruto began transforming during his training to control the Nine-Tails at the Falls of Truth, Yamato stated that he would try to suppress the beast, though it is unknown whether this would have been successful due to the transformation stopping through other means. In addition other Wood Release techniques are also capable of binding and suppressing the tailed beasts' power.

Background
The first person to attempt to make Hashirama's power his own was his rival, Madara Uchiha. Having used their confrontation at the Valley of the End to acquire a portion of Hashirama's flesh, Madara later applied it to the wound he sustained in his chest. In addition, Madara used the Demonic Statue of the Outer Path as a catylyst to cultivate Hashirama's cells, resulting in the creation of a flowering tree made up of Hashirama's artificial body. The White Zetsu stored within the Demonic Statue were later pulled out through the tree by Black Zetsu, each gaining the ability to use a weaker version of Hashirama's Wood Release in the process. Madara later used Hashirama's artificial body to repair the otherwise fatal wounds sustained by Obito Uchiha during his mission at Kannabi Bridge, giving him the ability to use Wood Release as well. When Madara was later reincarnated in a state beyond his prime by Kabuto Yakushi, he once again gained access to Wood Release.

After Hashirama's passing, Konohagakure once attempted to replicate Wood Release through implanting Hashirama's cells into various shinobi, which consistently ended in failure and the subject's death. Ultimately, the research was ceased and deemed forbidden. Orochimaru, another who desired the First Hokage's abilities, injected Hashirama's DNA into sixty children, with the sole survivor gaining the ability to use Wood Release as a result. Orochimaru also performed a similar procedure on Danzō Shimura by implanting the First's cells into his right arm. While Danzō was capable of using this power, his version appeared cruder and caused a significant drain of chakra with each usage, causing Danzō to avoid using it as much as possible. Orochimaru himself would later acquire this coveted ability after taking over the body of one of White Zetsu's parasite clones.

After reviving the Ten-Tails in an incomplete state, Madara and Obito were able to improve their control of the beast through the use of Hashirama's cells. Obito also demonstrated the ability to channel his Wood Release techniques through the Ten-Tails' body while attached to it.

Trivia

 * Wood Release parallels the real-life ninja art . One example of real-life mokuton-no-jutsu is Tanuki-gakure: the practice of climbing a tree and camouflaging oneself within the foliage.
 * Wood Release has had the most users and techniques out of all nature transformation kekkei genkai.
 * In the anime, the Moulding Mushroom appears to drain chakra from Wood Release users.
 * In the anime, Hashirama left behind a scroll detailing his various Wood Release techniques. Danzō later obtained this scroll and gave it to Yamato in the hopes that he would one day refine his Wood Release to Hashirama's level.
 * A replica of Hashirama's face formed on Danzō's right shoulder after Hashirama's cells were integrated into his body. Madara gained a similar replica of Hashirama's face on his chest after being reincarnated and modified by Kabuto, although it disappearred upon him being released from Kaguya Ōtsutsuki's control.