Hydrangea is a flowering plant native to southern and eastern Asia. Hydrangea grows as a shrub, usually 1 to 3 feet tall, distinguished by large, round flower heads resembling pom poms or mop heads. Most often the flowers are white but they can be blue, red, pink or purple. The color of the flower is actually influenced by the pH level of the soil, where an acidic environment produces bluer flowers, while alkaline soil produces more pink flowers.