There are many factors in how much water a given fruit tree will need to grow. Soil type, natural rain fall and the age of the tree are three important factors. You want the soil to retain moisture but drain adequately. There are certain types of fruit trees that do not withstand draught and require a lot of regular watering. Furthermore, fruit trees will require different amounts of water throughout their season.
This group of fruit--including peaches, nectarines, plums and apricots--prefers moist soil and does not tolerate drought. You need the soil to retain moisture to grow these fruits, according to Brenda Olcott-Reid, a writer for Flower & Garden Magazine. These trees should be watered twice a week during a growing season, according to Olcott-Reid, if there is no rainfall. Trees that are producing require at least 1 inch of water per week. After harvest, the tree's watering needs decline significantly.
Many types of apple trees are resistant to rotting and therefore can withstand rather wet soils. Apples have been so widely cultivated and bred for every condition possible. They are winter-hardy, resistant to collar rot and fungus, and are deep-rooted. If your soil is poor-draining, consider planting your apple tree on a mound or in a raised bed to protect it from getting too wet.
Pear trees need at least 1 inch of water per week without natural precipitation. If the soil is sandy and drains fast or if the tree is in full sun, the tree may need more. Pear trees are semi-tolerant of wet soils and require less maintenance than peaches or apples. Remove the weeds from around the trunks of your trees to maximize the amount of water they are actually getting.