Why is this the answer?

The answer is hair because this clever riddle uses fun word pictures to describe something that grows right out of your own head. The person who wrote this puzzle is pretending that your hair is just like a wild garden or a neat lawn outside. They want you to think of your own body as a landscape. Let us explore the clues one by one, like finding hidden treasures to solve a secret mystery. The first big clue says the answer "Grows from the ground, bushes and grass." When you first hear this, you probably picture a real plant, maybe beautiful flowers, a tall tree, or a big, leafy shrub. That is the trick of the riddle. For this puzzle, the "ground" is actually your scalp, which is the skin on your head. Your hair starts growing from this skin, just like little green plants start growing from the dirt in a garden. The riddle compares your long hair to "bushes and grass" when it starts to get long and a little bit messy. The next line talks about the colors: "leaves of yellow, red and brow." This clue is pointing out how different hair colors match the colors you see in nature. Think about the colors of hair you see on your friends and family. There is light blonde hair, which is like a shade of yellow. There is bright red hair. And there is brown hair, which the riddle cleverly calls "brow." Your hair can have all the same wonderful, beautiful colors as the leaves you see outside when the season changes in the autumn. Finally, the most fun clue is about trimming: "unruly plants, get the axe, trim the hedge back down." When a garden or hedge gets too long and wild, like a bunch of "unruly plants," a gardener has to use big clippers or shears to cut it back into a neat shape. The riddle uses the word "axe" to stand for the sharp scissors or clippers that your family or hairdresser uses on you. When they cut your hair, they are "trimming the hedge back down" to make it neat, short, and tidy again. Your hair keeps growing, just like grass in a yard, so you have to keep trimming it. All these funny plant clues work perfectly together to describe the hair on your head.