24 



BULLETIN 3 3, PORTO RICO EXPERIMENT STATION 



plants grown for wind protection and planting another as soon 

 thereafter as possible. In establishing a grove the first point need- 

 ing consideration is the maintenance of such wind protection as will 

 afford the most favorable conditions for tree growth and eliminate 

 the necessity of spraying. The second point is determining the best 

 method of improving the soil so that it will continue to support 

 growth during the many years the trees are expected to produce 

 profitable crops. 



The only treatment required by the tree mounds is that of keeping 

 them free from weeds and sufficiently well supplied with trash to 

 maintain a high degree of soil moisture. The soil will gradually 

 level down and after a few years will leave the trees with the 



Figure 15. — Tree which was planted on mound. Crown roots are well exposed and 

 trunk is free from gum disease 



crown roots entirely exposed. (Figs. 14 and 15.) These roots should 

 be carefully protected from injury. No implement of any kind 

 should be allowed in the proximity of the trees, and weeding should 

 be done by hand. Plows and harrows may be used 4 to 6 feet 

 from the tree trunk. Annual deep plowing is advisable, but inter- 

 mittent plowing is inadvisable. If plowing is deferred for several 

 years the large roots within reach of the plow are likely to be cut, 

 and the tree may thus be seriousty injured. 



The time and necessity for cultivation and the kind of implement 

 to be used vary with the different local conditions. In one 20-year- 

 old grove where the medium heavy clay soil is kept moist with water 

 from surrounding springs, plowing and cultivation have not been 

 practiced since the trees were young. Para grass {Pcmicum harbi- 

 node) grows luxuriantly in the grove and is cut at intervals. Most of 



