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 reappears in Plants vs. Zombies 2: It's About Time. This time, it is obtained after beating Wild West-Day 15. It retains the same functions as in Plants vs. Zombies, though it cannot restore the metal encasing provided by Plant Food in Wall-nuts and Tall-nuts.

Overview
Wall-nut First Aid allows the player to plant new Wall-nuts, Tall-nuts, Pumpkins and Infi-nuts 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 your 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

 * Players cannot plant a new Wall-nut, Tall-nut or Pumpkin over an undamaged one. They are categorized as undamaged until they begin to visually look like they have got bitten.
 * Even though the 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 the Wall-nut, Tall-nut, Pumpkin and Garlic to degrade, as well as the only offensive plant to do so.
 * Due to a possible glitch, Wall-nut First Aid no longer works in the endangered Wall-nuts in the Wild West Save Our Seeds levels.