the leafs at the top of a tree are always transpiring water via their stomata when the leaves evaporate water out of the leafs a negative pressure forms this causes water to be drawn up from the roots up a tall tree
water forms small bonds with each other which is cohesion so it can form small columns of water that are drown up capillary like structures called xylem.
the xylem is made with lignin which is insoluble to water allowing it to move continuously with less friction
water may also adhere to the side of the xylem preventing it from falling back down
hope that helps
