Ornate growth rates will vary greatly. whether it is cb or wc will play huge role.
My largest somewhere between 21 1/2 and 22 inches is 6 years old. Growth was quick to the 16 inch mark and then slowed down. Once it hit the 18Inch mark allot of the growth was in the girth. (i believe this one is WC)
My second is 1 1/2 years old and now at 15" albeit very slendar.(this one is CB)