210 MASS. EXPERIMENT STATION BULLETIN 170. 



of drought by cultivating around them, by supplying water, or by turning 

 luider the sod and applying manure heavily. Planting a crop around the 

 tree is also beneficial, but when this cannot be done conveniently, water 



may be supplied to the 

 roots through numerous 

 holes 1 or 2 feet apart and 

 12 or 15 inches deep, driven 

 in the soil by means of an 

 iron bar. In applying the 

 water it is important that 

 the feeding roots be 

 reached, and perhaps a 

 small amount of plant food 

 may be added at the same 

 time. Sometimes wells are 

 installed near the feeding 

 roots of trees; and tile 

 aqueducts can be placed 

 under trees at the time of 

 planting, through which 

 water can be supplied to 

 the roots of the tree. This 

 latter method would prove 

 valuable in periods of 

 drought for trees like the 

 European birch and others 

 which are greatly weak- 

 ened by any deficiency in 

 the water supply. 



FIG. 83. 



Red maple, alive with inferior foliage 

 at the top. 



Sun Scorch and Bronzing of Leaves. 



Sun scorch is a physiological trouble characterized by the wilting and 

 burning of the foliage of several species of trees during the spring and 

 summer. Sun-scorched leaves often present only a few dead, brownish 

 areas located on the margin of the leaves, or comprising more or less large 

 areas of dead tissues between the leaf veins. When a strong wind is 

 blowing the dead areas often disappear and the leaves present a lacerated 

 appearance. 



Sun scorch is caused by severe warm winds when the soil moisture is 

 low. It is more common in the spring and earlj^ summer, when transpira- 

 tion is at its maximum, the leaves transpiring more water than the roots 

 can obtain from the soil. As a result they become wilted, and those parts 

 of the leaves which fail to recover from the wilt die. Identical troubles 

 affect agricultural crops, ornamental shrubs, etc., although known by 

 different names. Tipburn of potatoes and onions, topburn of lettuce and 



