Wood Release

is a nature transformation kekkei genkai, a combination of earth and water. It was famously used by Hashirama Senju, and in fact is not known to have naturally occurred in anyone else. Because of Wood Release's power and versatility, there have been various efforts to reproduce it after Hashirama's death. Wood Release techniques are commonly affiliated with the Snake hand seal.

Usage
At its simplest, Wood Release allows the user to create wood, essentially converting their chakra into a source of life before, at it greatest, becoming mighty trees of various size and shape. The vegetation can sprout from the user's body or grow from the surroundings; Hashirama created a forest that served as a foundation for Konohagakure, contributing to his selection as First Hokage. Wooden constructs can also be created, ranging in complexity from cages to complete houses. It is not necessary that the created wood take any identifiable form, allowing users to focus on its inherent pliability to ensnare targets or its durability for brute force attacks.

Wood Release can produce very detailed, ornate constructs. Wood Release: Transformation essentially creates a costume around the user, allowing them to convincingly pass as another person. By using senjutsu, Hashirama could create a gigantic, many-armed wooden statue that he fully controlled; its barrage of punches were chiefly responsible for the Valley of the End's formation. Wood Release's most versatile application is the Wood Clone Technique, which makes a fully-functional duplicate of the user that is indistinguishable from the original and is even capable of performing other jutsu.

The Wood Release was also equally famous for its power to manipulate, suppress, and/or absorb a targets chakra. Hashirama's mastery of this ability earning him recognition as one of the few people able to fully control a tailed beast. This would be done by ensnaring a target with the Wood Release and upon such physical contact would then control the chakra until they were finally too weak to escape. Hashirama's usage of this skill let him subdue many of the tailed beasts, keeping them under his control and allowed him to distribute several to the early hidden villages.

Users
Hashirama possessed Wood Release naturally, which he used famously throughout his life. None of his descendants are known to have inherited his Wood Release, nor is he known to have inherited Wood Release from anyone; in the anime, his ancestor, Asura Ōtsutsuki, could perform Wood Release. Because of Wood Release's sheer usefulness, there have been various efforts to replicate it. In the anime, Konoha sanctioned several of these attempts, but all met with disastrous failure and further study was forbidden. Part of the difficulty lies in the vitality of Hashirama's cells, which can overwhelm and potentially kill those who try to use them.

Decades after Hashirama died, Orochimaru exhumed his body and infused sixty child test subjects with cells harvested from the remains in the hopes that one would prove able to use Wood Release. Only Yamato survived the process. Yamato became Hashirama's genetic double and thus could use Wood Release, but his version pales in comparison to Hashirama's. Most notably, he relies on the aid of Hashirama's necklace to suppress jinchūriki, something that is difficult for him otherwise.

Orochimaru also developed a method of infusing Hashirama's cells into part of a subject's body in order to grant them Wood Release. One such infusion was given to Danzō Shimura, applied to his specialised right arm. Danzō's Wood Release is quite taxing to perform and crude in function, for which reason he avoids using it directly; he more often uses Hashirama's cells to prolong the use of his implanted Sharingan. Kabuto Yakushi later furthers Orochimaru's research, enabling him to apply a graft of Hashirama's cells to Madara Uchiha's reincarnated body. Madara's Wood Release is much more extensive than Danzō's, being similar in scale and power to Hashirama's. In both Danzō's and Madara's cases, a replica of Hashirama's face grows on their body.

While he was alive, Madara acquired a sample of Hashirama's flesh. He initially applied it to himself in order to heal the injuries he received from Hashirama. Decades later, after acquiring the Rinnegan, Madara combined the flesh sample with the Demonic Statue of the Outer Path to produce a mindless clone of Hashirama. From this clone he could harvest a substance capable of replacing lost limbs, giving recipients, such as Obito Uchiha, limited Wood Release abilities. Madara used this same substance to make the White Zetsu Army, rendering each Zetsu an application of Wood Release. Orochimaru, by taking over one of these White Zetsu, finally gains Wood Release for himself.

Moegi Kazamatsuri is able to use Wood Release in adulthood, but it's not known how.

Trivia

 * is a real-life ninja art where the user climbs a tree and camouflages themselves within the foliage.
 * Hashirama possessed a Regeneration Ability, which passively healed all of his injuries. The ability itself was not Wood Release and it has never been stated to be part of his kekkei genkai, but efforts to reproduce his Wood Release also reproduce this Regeneration Ability. In addition, people with Hashirama's genetic tissue transplanted also no longer required any food or water to survive. However, it is also unknown if this trait is related or if Hashirama himself was also endowed with the latter.
 * Also, it is unknown if Naruto gained this self-sustenance capacity or the Wood Release from his own artificial arm of Hashirama' genes.
 * 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.
 * In Akatsuki Hiden, earth and water natures are also components in Mud Release. Because Wood Release is so much more famous, few people have ever heard of Mud Release.
 * Those who are in possession of Hashirama's cells along with a Mangekyō Sharingan are able to use the latter more extensively than those without the cells, as Danzō could use the Kotoamatsukami with a greatly reduced cool-down period, and Obito could use the Kamui repeatedly without signs of eyesight deterioration.
 * In the novelisation of Boruto: Naruto the Movie, Katasuke uses Wood Release through his Shinobi Gauntlet. His Wood Release is in turn absorbed by Momoshiki Ōtsutsuki.