FERTILIZING AND WATERING TREES 17 



Established trees 



With normal rainfall, established trees can obtain an ade- 

 quate supply of water from the soil. During droughts or extended 

 dry periods in the summer, all trees are benefited by watering. 

 Trees weakened by injury, disease, or insect pests will be espe- 

 cially benefited. The relative moistness or dryness of the soil 

 can be determined by inspecting a soil core removed with a spade 

 or soil profile tube. Soil taken from different depths should be 

 examined while being crumbled between the fingers. 



Water applied to the soil surface fills the capillary spaces 

 from the top down. A surface sprinkling daily to wet the soil to 

 a depth of 1 inch or so is of little value to trees or grass, since 

 most plant roots are at greater depths and remain in dry soil. 

 Water should be applied less frequently and in larger quantities. 



Water should not be applied more rapidly than the soil will 

 absorb it. If applied too rapidly, water will be lost through runoff 

 and will erode the soil surface. Heavy clay soils are difficult to 

 wet and slow to dry out. They require more water per application 

 and applications at less frequent intervals than do sandy soils. 

 Sandy or light soils are easy to wet, but because their water- 

 holding capacity is less, they must be watered more frequently 

 than heavier soils. 



The most satisfactory means of supplying and distributing 

 uniformly an adequate amount of water to an established tree is 

 with a garden hose and an oscillating lawn sprinkler. To thor- 

 oughly wet the soil, the equivalent of 2 inches of rainfall should 

 be applied. During prolonged dry periods in the summer this 

 should be repeated at intervals of 2-3 weeks. Coffee cans placed 

 near the sprinkler make handy gauges for measuring the amount 

 of water applied. If water begins to run off the surface before 

 the intended amount is supplied, half the volume should be ap- 

 plied one day and the other half the following day. 



Other means of supplying supplemental water are soaker 

 hoses and root-watering needles. Soaker hoses are best used in 

 limited areas, such as border plantings, hedge plantings, or foun- 

 dation plantings. A root-watering needle is conveniently used 

 around small trees or shrubs. The needle has the advantage of 

 injecting water into the immediate area of the roots, but since 

 only a limited amount of soil is watered at each site, the needle 

 must be moved at frequent intervals. 



