I've been able to take out 2 Tar pit's by using Wooden Arrows to bait the Growth's over one at a time. When it approaches, start circling it constantly and wait for it to attack, it will miss as long as you keep strafing it. It's attack has a cooldown of about 5-6 seconds so it's safe to attack for a moment. Use any weapon you want.

Do not block or dodge their attacks, just move calmly and sprint when needed.