Considering that trees grow throughout their lives, a tree reaches its full-size on the day it dies. A white oak tree can reach its full size after three centuries while a redbud tree reaches its full-size when it's about 20 years old.
Trees reach maturity at different times. Red oak trees reach maturity when they are about 25 years old. Apple trees take from six to 10 years, depending on whether they are semi-dwarf or standard. Some trees reach maturity when they are a certain size. The redbud reaches maturity when it reaches a height of between 20 and 30 feet.