In the second year, the tree will grow 2 x 1.5 = <<2*1.5=3>>3 feet.
In the third year, it will grow 3 x 1.5 = <<3*1.5=4.5>>4.5 feet.
In the fourth year, it will grow 4.5 x 2 = <<4.5*2=9>>9 feet.
In the fifth year, it will grow 9 / 2 = <<9/2=4.5>>4.5 feet.
When the tree is 5 years old, including the first year's growth, it will be this tall 2 + 3 + 4.5 + 9 + 4.5 = <<2+3+4.5+9+4.5=23>>23 feet.
#### 23