The care of a tree depends on the species, its size, at what season of year we are living, the type of soil (dry, humid or sandy) and the surrounding environment.
If the tree is newly planted it will need more water in the hot seasons, but beware, if you put too much water you can suffocate the roots and they will rot, this will also cause them to grow on the surface since they do not need to go underground to find water. It should be watered until its roots are abundant and it can have autonomy, in other words, there is no need to water it. One way to make sure you have the necessary water is to inspect the soil about 5 centimeters down; if it is wet but not too wet you are doing a good job taking care of your tree.
Sometimes it is necessary to fertilize the soil if it does not have enough nutrients, this can easily be done at home preparing a mixture of organic waste such as vegetables or fruits, you can also add ashes, leaves of trees or the same cut grass.
Once a year or every two years you can add about 2 kilograms of the fertilizer you prepared around the tree and mix it with the earth, do it gently so as not to damage the roots that are on the surface.