Wall-nut First Aid

Wall-nut First Aid is an item that can be purchased from Crazy Dave's Twiddydinkies for $2000 after the player has beaten Adventure Mode. It lets the player plant new seeds of specific plants over the old, damaged ones and fully restore their health.

Wall-nut First Aid returns in Plants vs. Zombies 2: It's About Time as an upgrade. This time, it is obtained after beating Wild West - Day 15 after version 1.7 and after unlocking the one-key gate pre-1.7 instead of paying coins. It retains the same functions as in Plants vs. Zombies, although it cannot restore the metal encasings provided by Plant Food in Wall-nuts, Tall-nuts, and Pea-nuts.

Overview
Wall-nut First Aid allows the player to plant new Wall-nuts, Tall-nuts, Pumpkins, Infi-nuts, Pea-nuts, Sweet Potatoes, and Chard Guards on top of damaged plants of the same kind without having to dig them up first. This allows the player to replace a defensive plant when a zombie is chewing on it without digging it up and giving the zombie a chance to escape. Wall-nut First Aid does not work on any other plants, including Garlic.

Tall-nuts still cannot replace Wall-nuts without first digging up the Wall-nut, so keep this in mind if the player's strategy is to start off with cheaper Wall-nuts before replacing them with stronger Tall-nuts. Planting a Pumpkin around the Wall-nut before digging it up would keep the space protected during the swap, but this would be a waste of sun, so it would make more sense to wait until there are no zombies nearby.

For the achievement Sunny Days, it is wise to have Wall-nut First Aid purchased, so you can easily replace the Wall-nuts or Tall-nuts the zombies are chewing on, while collecting sun as well.

Trivia

 * The player cannot plant a new Wall-nut, Tall-nut, Pumpkin, Sweet Potato, or Pea-nut over an undamaged (losing leaf for Chard Guard) one. They are categorized as intact until they begin to visually look like they have been bitten.
 * Even though Garlic is a defensive plant, the Wall-nut First Aid does not work on it. The same happens with Spikerock, the only plant other than defensive plants that degrades.
 * Wall-nut First Aid does not work on the endangered Wall-nuts in the Save Our Seeds levels.
 * However, it work on endangered Chard Guard.
 * Before the 2.8 update, it does not work on Pea-nut when it is on the second degrade.