Lettice

Lettices are defensive plants that produce flimsy walls for the player to drag to keep back zombies.

Overview
When planted, Lettice comes with a wall already made. The player can then drag this wall anywhere on the board to place it (it cannot be moved after being placed down). Here, the wall can keep back zombies, but it falls once a certain amount of zombies start acting on it. The amount varies on the strength of the zombies: If there are multiple zombie types currently acting on a Lettice wall, then the proper rate will be applied (ie. one imp is equivalent to half a regular zombie, so it takes 2 imps to fill in the strength of 1 zombie).
 * It takes 16 imps to push down a wall.
 * It takes 8 regular zombies to push down a wall.
 * It takes 4 muscular zombies (Troglobite, Jurassic Bully, etc.) or robots to push down a wall.
 * It takes 1 Gargantuar to smash a wall.

Once the amount of strength needed is forced upon the wall, it goes down. This process is not immediate however; there is a 3 second delay between the requirement met and the wall being defeated. If a zombie dies between this period, and it would bring the strength below tipping point, the wall will still fall.

Once the zombies push down a wall, the wall will fall down on the tile behind it (towards the house), dealing 1.5 damage points to all zombies on that tile.

Lettice regenerates a new wall every 15 seconds. If a Lattice is fully eaten while it holds a wall, then the wall will appear in Lettice's place.

Lettice is based off of lettuce. Its name is a portmanteau of "lettuce" and "lattice," in reference to the design of its wall. Its name is not to be read as "Lett-ice," as it is not an ice plant.

Plant Food Ability
Using Plant Food on a Lettice will cause it to be permanently boosted. In this boosted state, it creates steel walls. These walls take double the strength to push down (32 imps, 16 zombies, 8 musculars, and 2 Gargantuars). However, this increases to wall-production time to 25 seconds.

Strategies
Lettice is effective in stopping smaller groups of zombies. This means they do better in between huge waves, where the zombies are less plentiful. They also work better away from the very front of the lawn, as the more distance a zombie has to walk, the more likely they'll be taken out, which reduces the chances of a Lettice wall being pushed down.

Lettice is ineffective against Turquoise Skull Zombies and Explorer Zombies, as they will be able to burn the wall instantly. The same applies to All-Star Zombies and Rodeo Legend Zombies as well.

Trivia

 * Because it takes a certain amount of zombies to take down a Lettice wall, zombies can chew on it forever without the wall disappearing.
 * This means that the wall has virtually infinite health.
 * The wall can be placed anywhere, including the water and charred tiles.