Plant Food is a game mechanic in Plants vs. Zombies 2 that gives plants powerful boost of their attacks/defenses. The abilities are usually a stronger display of their function or at least something related to it.

It can be obtained in the Shop Stand or in the server book item itself.

The shovel is an item available in Shop Stand that is used to dig up plants.

when it comes to Lilypad and plant pot, you will have to interact with them and not by a hold press of the item.

Note: If you are in survival mode, you can use the shovel to obtain the plant you just planted.