Imagine for a moment that a plant (let's say a maple tree, though any plant will do), has unlimited energy. There's no conversion of sunlight or anything - the energy is just there, being soaked directly into the tree. This energy is infinite, as much as the tree needs.
How fast could the tree grow? If you have an elf 'tree-shaping' this way, could he theoretically form something within five minutes? Or is it more like five years?
*Note: Despite the elf illustration, magic is not a factor and should not be considered. The only factors are unlimited energy and the plant involved.