Quote Originally Posted by BobBong
There are such things as dwarf plants.. Thing will only get so large.. mature then flower. It's happened to me..
Only autoflowering strains have the ability to do this. They reach a certain calendar age and then flower.

Dwarf plants are rare. Most likely if you are running a non-autoflowering strain, and it stays small, it is a problem with soil pH or the plant is root-bound.