Originally posted by electricdawn:

The most effective way for me to fight growths is to wait for them to start shooting, then dodge sideways to evade them. I then run in using their recovery down time to kill them quickly. They're completely helpless during that (very) short time.

You also can prevent them from spawning again, by just placing a camp fire right at the border of the tar pit.

I do the same but they are weak to fire so I use flaming arrows. Roll out of the way and fire, repeat. Takes about 3 fire arrows to kill a growth. You don't even need poison resistance. Its possible to dodge all of their projectile attacks.