192 HORTICULTURE FOR SCHOOLS 



As the almond blooms very early in the spring (February 1 

 to March 20, depending on the variety and district), it is very 

 likely to be injured by spring frosts except in the most favor- 

 able locations, such as the low foothill regions and somewhat 

 elevated portions of the large interior valleys of California, 

 where the air drainage is good and frost not likely to occur 

 at blooming time. 



All commercial varieties of almonds are self -sterile, insofar 

 as they have been tested, and some have been found to be 

 inter-sterile. The varieties for inter-planting and for pollina- 

 tion, therefore, must be selected very carefully. 



The almond is propagated by budding upon almond or 

 peach stocks. It thrives and produces best on deep well- 

 drained soils. A moderate amount of moisture is necessary. 



The California Almond Growers' Exchange is the principal 

 marketing agency for almonds grown in this country. This 

 cooperative organization is similar in its scope to the other 

 farmers' cooperative agencies mentioned in Chapter XIX. 



The almond is placed on the market both in the shell and 

 as a shelled product. Almonds and almond paste are used 

 in the making of many confections. 



The almond tree is subject to few diseases or insect pests. 



Crown-gall is rather common (see Chapter XVII) and 

 shot-hole fungus sometimes appears. The latter is controlled 

 by spraying with lime-sulfur solution. The most common 

 insect pest is the red-spider, which multiplies rapidly in the 

 hot summer months. Sulfur is applied as often as the red- 

 spider becomes troublesome. 



284. The walnut. Black walnuts of one kind or another 

 have been found in nearly every state and in parts of Canada. 

 The Persian (English) walnut, has been tested in many 

 sections of the United States, but did not thrive except 

 in favored districts. It is now grown commercially in the 

 Pacific states and especially in California. The latter state 

 has approximately 75,000 acres of walnut plantings. On 



