The second week it grew twice as much as the first week, so 2 * 2 inches = <<2*2=4>>4 inches.
The third week it grew 4 times as much as in the second week, so 4 * 4 inches = <<4*4=16>>16 inches.
In total, it grew 2 inches + 4 inches + 16 inches = <<2+4+16=22>>22 inches.
#### 22