You still have to manually target the the tree growth for it to spawn trees, but yes once they are stuck and you attempt to use it out of range there is no animation of fungal growth but trees will still spawn and no energy is used so you can use this to spawn an unlimited amount of trees in any spot on the map as fast as you can spam click the ability. This normally would not happen if they are not stuck and they would need to get in range and would use up energy.