BROAD-LEAVED EVERGREENS 



339 



for acid-soil plants. In very sandy soils for which so little peat 



is available that the evergreens suffer for nourishment, the 



following special acid 



fertilizer devised for blue- ^^ , . 



berries and cranberries \\ I ^> '^^■ 



would probably do well 



for rhododendrons, ap- .. ^^ . ,,^ 



plied at the rate of an ' 



eighth to a fourth of a 



pound to a square 



y^^^* Pounds /^^N«^^-^;>^ 



Nitrate of soda 17 ( ^Af-ti^^^^^^^^^i--' 



Dried blood 23 ^^Zz^^^S-^:;^lllf~--^ ' ^' '"> 



Steamed bone 34 I M(| 



Phosphate rock 34 ^ ** '^ 



Potash 17 



Experiments in \ "§ \ ~~" I 



the last two years 97. Beneficial efifect of aluminum sulfate on Rhodo- 

 have shown that an ^^"^°° maximum.-Half natural size 



ordinary garden or greenhouse soil, well suited to roses, but 

 fatal to rhododendrons, can be acidified by the application of 

 crude aluminum sulfate, and will then nourish rhododendron 

 seedlings almost as well as peat and sand (see Figs. 96, 97). f 



*From page 20 of "Directions for blueberry culture, 1921," Bull. 974, U. S. Dept. 

 Agr., 24 pages and 29 plates. 



fFor a detaUcd account of these experiments, see "The effect of aluminum sulphate 

 on rhododendron seedlings," 1923, Bull. 1, Amer. Hort. Soc, 6 pages and 5 plates. 



Fig. 96. Injurious Effect of Ordinary Rich Garden Soil on a Rhododendron. In 

 early May, healthy seedlings of Rhododendron maximum were set in 2-inch pots in an 

 ordinary greenhouse or fertile garden soil composed of equal parts, by bulk, of loam, 

 well-rotted manure, and sand. Other exactly similar plants were potted in a soil con- 

 sisting of two parts of peat to one of sand. In June of the following year, when the 

 photograph was made, the plant at the left, in the ordinary fertile garden soil, had 

 made no growth, while the plant at the right, in the strongly acid peat soil, had made 

 normal and luxuriant growth. 



Fig. 97. Rhododendron maximum a Year after Treatment with Aluminum Sulfate. 

 The plant at the left (same as in Fig. 96), potted in a fertile garden mixture on May 

 3, 1921 which is not suited to rhododendron culture, had made no growth when it was 

 photographed on June 3, 1922. The plant at the right, exactly similar to the other 

 in history and treatment except that it had received one-third gram of aluminum sul- 

 fate in 10 cubic centimeters of water on May 27, 1921, made luxuriant growth, 

 almost as good as the plant in the acid peat-and-sand soil illustrated in Fig. 96. 



