Trees and bushes are a little different from other crops. You can place fruit trees and berry bushes in your Backyard and you can collect fruit or berries from them for four times in a row and three times in a row thereafter post watering them.
After providing fruit for the third time, the trees and bushes need to be watered. You can water them yourself by tapping on the watering can. You need goodies to water trees and bushes.
You can ask your friends and fellow chefs to help you with watering them if you do not want to spend goodies. Just tap the "help" sign next to the tree / bush that requires to be watered and any other fellow chefs who visit your restaurant will be able to water them.
Note: You can also water the plants with the help of Goodies.