Wood release is created by channeling water chakra in one hand and earth chakra in the other, causing them to combine with a handseal, which was shown by Yamato.
Wood release is weak to lightning due to it running through it, shredding it completely. Such as a bolt of lightning on a tree. It is also neutral to fire.
Wood release is strong against Bijuu chakra as we seen in the manga, as well earth due to it breaking earth apart from within. Wood release is strong against water, due to it being highly resistant against it.