THE AVOCADO 33 



vation destroys many of them, thus cutting off a large part 

 of the tree's food supply. On shallow soils the most healthy 

 and vigorous trees are those which are mulched. The mulch 

 should extend at least two feet in each direction from the 

 trunk of the young tree, and as the latter increases in size 

 and its roots reach out on all sides, the mulch must be en- 

 larged to be always a little wider than the diameter of the crown. 



Mulching serves two purposes : it prevents the soil from 

 drying out rapidly, and it protects the delicate feeding roots 

 from injury due to excessive heating of the soil. This protec- 

 tion is of particular importance in Florida, where in many 

 places the land is sandy and becomes exceedingly hot if exposed 

 to the sun. 



When the trees are of mature size, the shade furnished by 

 their own foliage, together with the fallen leaves which carpet 

 the ground, aids materially in maintaining the soil in good 

 condition; but additional loose material, especially during 

 the summer, is highly desirable. 



The use of green cover-crops between the rows is decidedly 

 beneficial, but they must not be brought close enough to the 

 trees to rob them of their food. In Florida, cowpeas and 

 velvet beans have been used for this purpose, cowpeas being 

 preferred. A clump of pigeon peas (Cajanus indicus) planted 

 four feet to the south of each young tree will provide shade 

 during the first summer or two, serve as a protection from wind, 

 and aid in enriching the soil. In California, purple vetch 

 (View, atropurpurea) , common vetch, and the other cover- 

 crops used in citrus culture will probably prove satisfactory. 

 Up to the present time they have not been extensively tried 

 in connection with avocado culture. 



Fertilizer. 



Little systematic attention has yet been given to this subject. 

 Not only is the question difficult, but it is also one of the most 



