Their life span is completed in one year. Most annual plants are herbs. The herbs remain in a small size and their stems are usually green and strong. Biennial plants have a life span that is completed within two years. Biennial plants do not reproduce flowers and seeds until their second growing season.
Perennial plants live for more than two years.
Perennials include trees and shrubs and many herbs. Stems and leaves of perennial herbs die each winter but they regrow during the next growing season. One of the most interesting things I found was that there were a lot of plants that were harmful. Symptoms include nausea, dizziness, convulsions, and paralysis. The Black Locust is also poisonous.