If winter rainfall has been adequate, trees should not need to be irrigated more than once a month during their second year. After that, most trees can survive with only one or no irrigations, although they would probably do better with monthly applications. It is essential to maintain an area free of turf and weeds around tree trunks, because turf and weeds compete for water and nutrients, and some produce chemicals toxic to other plants. A small turf-free area around a tree also reduces the need for mowers to come close. This clear area must be at least one-foot in radius.
Larger areas add little benefit.
After four or five years, tree roots are extensive enough that other plants close to their trunks are not a problem, although mower operators should still exercise caution. Keep mulches at least two inches away from the trunks of trees to minimize disease and rodent damage. A wide range of organic and inorganic materials can be used. Unfortunately, most bulky mulches are not satisfactory for trees in turf that is mown, but some plastic planting-basin covers will reduce turf and weed growth. Power string trimmers are great for edging around borders and plants, but many trees have been fatally girdled by them.