In some parts of the Arctic the ground is covered with bright-colored flowers during the short summer. These little plants have very short stems. They must stay close to the ground, because the earth is warmer than the biting winds that blow above it. Even some rocks have plants growing on them. These rock plants are called lichens. Lichens will grow on the bare rocks. Yellow reindeer moss is really a lichen. It grows slowly, but often grows over six inches (15 cm) tall. It is spongy and full of water. This plant is the summer food for reindeer.