Yuck! is the 4th campaign mission on the zombie side.
You will be tasked with defending against 5 waves of plants in the exact same way you would do in Garden Ops. You can choose up to 3 AI zombies to help you in this battle. Any zombies you have previously unlocked are available to be chosen and you can switch between any of them using
. The first 4 waves throw random small plants and lots of sunflowers. They heal themselves pretty nicely but do very little damage to you and your team. Wave 5 however sends a super boss sunflower after you. This guy is huge and powerfull. His beam deals more damage than a normal sunflower. After you have defeated 5 waves you will teleport back to Dr. Patient (the quest giver) and the achievement will unlock.