The century plant will stay at ground level at about the same height for about 30 years, and then it will grow a giant stock from 15 to 30 feet high out of the middle of the plant, and it will have beautiful yellow flowers, which will drop seeds which will grow the next generation of century plants. If you have a century plant in your yard, at some point it will do this, and you can collect the seats and grow more century plants. Some people also call these sentry plants.