Water is essential to tree survival. Trees are composed mainly of water, and it is a key ingredient in photosynthesis, the tree’s food-making process. Minerals and nutrients from the soil are transported to the leaves by water. Too little water reduces photosynthesis, mineral uptake, and transport of nutrients in the tree, and can result in death of the tree. Too much water can also lead to tree death because the roots must have oxygen to function. Not too little, not too much— just right. Healthy trees require a regular and planned irrigation routine. Sporadic, random, shallow watering leads to shallow rooting and water stress and increases susceptibility to insect and disease damage. How water is applied, how much is applied, and how often it is applied are the key factors in tree irrigation. To determine what is right for the tree, first examine the site. What type of soil is the tree growing in? Soil is the storehouse for the tree’s water and may range from coarse, loose sand or cinder to fine, compact, heavy clay. Clay soil makes a ball that holds together when squeezed in the hand. Clay soils can be hard to dig, especially when dry, but they hold water very well. Heavy soils and clay soils often hold too much water and too little air for many trees. Clay soils can become very hard when they dry, and may crack. Sandy soil, when squeezed, makes a ball that falls apart easily. Sand can be dug easily, but does not hold water well. Water penetrates deeply but not very widely in sand. The “ideal” soil is a mixture of sand, clay, and silt, known as loam.